Do houseplants have beneficial effects on health?

Do houseplants have beneficial effects on health?


Having and caring for houseplants can:

  • Reduce psychological and physiological stress.
  • Improve recovery after surgery.
  • Increase attention and concentration.
  • Increase creativity and productivity.

In our modern societies, where everything seems to go faster and faster, many feel the harmful effects of stress and anxiety; however, this appears to have increased since the start of the COVID-19 pandemic. During spring and summer 2020, many Quebecers took advantage of the beautiful weather to recharge their batteries in nature, either by visiting a park, camping, walking in the forest, or renting a cottage in the countryside. As winter approaches, contact with greenery becomes scarce and travel to regions with warmer climates is risky and strongly discouraged by Public Health. Apart from hiking in our beautiful coniferous forests, one of the only possible contacts with greenery during this long winter will be the green plants we take care of in our homes. Houseplants decorate and bring a natural touch to our homes, but do they have proven beneficial effects on our physical and mental health.

Stress reduction
A systematic review in 2019 identified some 50 studies on the psychological benefits of houseplants, most of these studies being of average quality. The most noticeable positive effects of houseplants on participants are an increase in positive emotions and a decrease in negative emotions, followed by a reduction in physical discomfort.

In a randomized, controlled crossover study of young adults, participants saw their mood improve more after transplanting an indoor plant than after performing a task on the computer. In addition, participants’ diastolic blood pressure and sympathetic nervous system activity (physiological response to stress) were significantly lower after transplanting a plant than after performing a computer task. These results indicate that interaction with houseplants can reduce psychological and physiological stress compared to mental tasks.

Plants in the office
In 2020, a Japanese team carried out a study on the effects of plants in the workplace on the level of psychological and physiological stress of workers. In the first phase of the study (1 week), workers worked at their desks without a plant, while in the intervention phase (4 weeks), participants could see and care for an indoor plant that they were able to choose from six different types (bonsai, Tillandsia, echeveria, cactus, leafy plant, kokedama). Participants were instructed to take a three-minute break when feeling tired and to take their pulse before and after the break. During these 3-minute breaks, workers had to look at their desks (with or without an indoor plant). Researchers measured psychological stress with the State-Trait Anxiety Inventory (STAI). The participants’ involvement was therefore both passive (looking at the plant) and active (watering and maintaining the plant).

The psychological stress assessed by STAI was significantly, albeit moderately, lower during the intervention in the presence of an indoor plant than during the period without the plant. The heart rate of the majority of patients (89%) was not significantly different before and after the procedure, while it decreased in 4.8% of participants and increased in 6.3% of patients. It must be concluded that the intervention had no effect on heart rate, which is an indicator of physiological stress, although it slightly reduced psychological stress.

A study of 444 employees in India and the United States indicates that office environments that include natural elements such as indoor plants and exposure to natural light positively influence job satisfaction and engagement. These natural elements seem to act as “buffers” against the effects of stress and anxiety generated by work.

Recovery after surgery
It appears that houseplants help patients recover after surgery, according to a study in a hospital in Korea. Eighty women recovering from thyroidectomy were randomly assigned to a room without plants or to a room with indoor plants (foliage and flowering). Data collected for each patient included length of hospital stay, use of analgesics to control pain, vital signs, intensity of perceived pain, anxiety and fatigue, STAI index (psychological stress), and other questionnaires. Patients who were hospitalized in rooms with indoor plants and flowers had shorter hospital stays, took fewer painkillers, experienced less pain, anxiety, and fatigue, and they had more positive emotions and greater satisfaction with their room than patients who recovered from their operation in a room without plants. The same researchers performed a similar study in patients recovering after an appendectomy. Again, patients who had plants and flowers in their rooms recovered better from their surgery than those who did not have plants in their rooms.

Improved attention and concentration
Twenty-three elementary school students (ages 11–13) participated in a study where they were put in a room with either an artificial plant, a real plant, a photograph of a plant, or no plant at all. The participants wore a wireless electroencephalography device during the three minutes of exposure to the different stimuli. Children who were put in the presence of a real plant were more attentive and better able to concentrate than those in the other groups. In addition, the presence of a real plant was associated with a better mood in general.

A cross-sectional study of 385 office workers in Norway found a significant, albeit very modest, association between the number of plants in their office and the number of sick days and productivity. Workers who had more plants in their office took slightly fewer sick days and were a bit more productive on the job. In another study, American students were asked to perform computer tasks, with or without houseplants, in windowless rooms. In the presence of plants, participants were more productive (12% faster in performing tasks) and less stressed since their blood pressure was lower than in the absence of houseplants.

What about air quality?
Do plants purify the air in our homes? This is an interesting question since we spend a lot of time in increasingly airtight homes, and materials and our activity (e.g. cooking) emit pollutants such as volatile organic compounds (VOCs), oxidizing compounds (e.g. ozone), and fine particles. A NASA study showed that plants and associated microorganisms in the soil could reduce the level of pollutants in a small, sealed experimental chamber. Are these favourable results obtained in a laboratory also observable in our homes, schools and offices? Some studies (this one for example) conclude that plants decrease the concentrations of CO2, VOCs and fine particles (PM10). However, these results have been called into question by researchers (see this study) who question the methodology used in previous studies and who believe that plants are ineffective in improving the indoor air quality of our buildings. According to these researchers, it would be better to focus research efforts on other air-cleaning technologies as well as on the beneficial effects of plants on human health.

Indoor plants can provide health benefits by reducing psychological and physiological stress. Owning and maintaining plants can improve mood and increase attention and concentration. New, more powerful and better controlled studies will be needed to better identify and understand the effects of plants on human health.

The social environment, essential for mental and physical health

The social environment, essential for mental and physical health


  • A large number of studies have established a strong association between an inadequate social network and an increased risk of developing a variety of diseases and dying prematurely.
  • One of the major challenges in the fight against infectious diseases such as COVID-19 is therefore to find a balance between the measures necessary to prevent viral transmission while maintaining a sufficient level of social interaction for the mental and physical well-being of the population.

The containment of the population in response to the COVID-19 pandemic has made it possible to substantially reduce the number of people infected with the SARS-CoV-2 coronavirus. According to recent estimates, the measures implemented to contain the epidemic have prevented around 530 million infections worldwide, including 285 million in China and 60 million in the United States. However, these measures mean that less than 4% of the population seems to have been infected with the virus, which means that the fight is far from won and that we must remain vigilant if we want to avoid further waves of infection.

One of the main challenges in the fight against COVID-19 is to find a balance between the measures necessary to prevent viral transmission while maintaining a sufficient level of social interaction for the well-being of the population. Humans are social animals and much has been said, and rightly so, about the deleterious effects of confinement on mental health. This is confirmed by the results of a survey recently published in the Journal of the American Medical Association (JAMA). Using a questionnaire developed to assess the presence of mental disorders (Kessler 6 Psychological Distress Scale), researchers noted that in April 2020, during the COVID-19 epidemic, 14% of American adults exhibited serious symptoms of psychological distress compared to 4% in 2018. These symptoms were particularly common in young adults aged 18 to 29 (24%), as well as among low-income households (less than $35,000 per year).

Physical harm
It should also be remembered that the social environment has a huge influence on physical health in general. It has long been known that certain parameters of our social life, in particular the level of social integration, socioeconomic status and negative experiences at an early age, are among the main predictors of the state of health of individuals and their life expectancy. Disruptions to life in society, such as those caused by a large-scale epidemic, can therefore have negative consequences on the health of the population in the medium and long term.

A large number of studies have established a very clear association between social adversity (negative experiences of life in society) and an increased risk of developing a variety of diseases and dying prematurely (Figure 1). Three main aspects were studied:

Social integration. Studies show that the level of social integration (positive interactions with family, friends and/or colleagues, emotional and physical support from those around them) increases people’s life expectancy by 30 to 80% (Fig. 1B). Conversely, poor social integration (also called social isolation) is associated with an increased risk of several diseases, in particular cardiovascular disease (Fig. 1E), and an increase of about 50% of overall mortality, a risk similar to that associated with well-known risk factors such as obesity, hypertension or sedentary lifestyle (see also our article on this subject). This impact of the level of social integration on health appears to be biologically “programmed”, as similar effects have been observed in a large number of social animals, including primates, rodents, whales and horses. On the scale of the evolution of life on Earth, the link between the degree of social integration and life expectancy has therefore existed for several million years and can consequently be considered as a fundamental characteristic of the life of several species, including ours.

Socioeconomic status. Another consequence of social distancing measures is to disrupt economic activity and, at the same time, cause a drop in or even a loss of income for many people. It has long been known that there is a close correlation between socioeconomic inequalities (generally measured by household income) and the health of the population. For example,  as early as the 1930s, it was observed in the United Kingdom that the risk of death from cardiovascular disease was twice as high among men of lower social class compared to those of the upper classes. Studies since that time have shown that these income differences are associated with an increased prevalence of a large number of diseases (Fig. 1D) and a significant decrease in life expectancy (Figure 1A). In the United States, a comparison of the poorest 1% of the population to the richest 1% of the population indicates that the difference in longevity is of the order of 15 years for men and 10 years for women. This difference may be less pronounced in countries with a better social safety net than Americans (such as Canada), but nevertheless remains significant. In Montreal, for example, the life expectancy of residents of Hochelaga-Maisonneuve was 74.2 years in 2006–2008, compared to 85.0 years for residents of Saint-Laurent, a gap of almost 11 years.

Negative experiences of childhood. The first years of life represent a period of extreme vulnerability to the external environment, both physical and social. One of the dangers associated with periods of prolonged confinement is exposing some children living in precarious conditions to an increased risk of injuries. Unfortunately, this appears to be the case with the COVID-19 epidemic, as U.S. pediatricians recently reported an abnormal rise in children admitted to hospital with severe physical trauma.

This is an extremely worrying situation, as it has been clearly shown that social adversity at an early age is associated with an increased risk of several diseases, including cardiovascular disease, stroke, respiratory disease and cancer (Fig. 1F), as well as a greater susceptibility to viral infections and premature mortality (Fig. 1C). These negative impacts that occur during childhood appear to form a lasting imprint that persists throughout life, even when there is an improvement in living conditions. For example, a study of American doctors reported that subjects who had lived in early childhood in a family with low socioeconomic status had a twice as high risk of premature cardiovascular disease (before age 50), even if they had achieved high socioeconomic status in adulthood.

Figure 1. Association between social adversity and the risk of disease and premature death. (A) Life expectancy at age 40 for American men and women by annual income. (B) Proportion of subjects alive after 9 years of follow-up according to the social network index (quantity and quality of social relations) (n = 6298 people). (C) Average age at death based on the number of adverse childhood experiences (ACEs) (n = 17,337 people). (D) Prevalence of various diseases among American adults as a function of their annual income (n = 242,501 people). (E) Risk of disease by level of social integration among American adults (n = 18,716 people). (F) Risk of disease based on the number of adverse childhood experiences (ACEs) (n = 9,508 people). From Snyder-Mackler et al. (2020).

Role of chronic stress
Several studies indicate that stress plays an important role in the association between social adversity and the increased risk of disease and premature death. All forms of social adversity, whether it is social isolation, insufficient income to meet children’s needs or childhood trauma, are perceived by the body as a form of aggression and therefore cause activation of physiological mechanisms involved in the stress response, such as the secretion of cortisol and adrenaline. For example, exposure to some form of social adversity has been shown to be associated with epigenetic changes (DNA methylation) that alter the expression of certain inflammatory genes involved in the stress response. Studies also show that individuals who are socially isolated tend to adopt behaviours that are more harmful to health (smoking, sedentary lifestyle, excessive drinking, etc.), which obviously contributes to reducing life expectancy.

Overwork can increase the risk of cardiovascular disease

Overwork can increase the risk of cardiovascular disease

In Canada, as in most industrialized countries, the proportion of time spent working has decreased considerably since the beginning of the 20th century. At that time, most people worked around 3,000 hours per year (equivalent to 60–70 hours per week), much more than the 1,800 hours worked on average by today’s workers (Figure 1). This reduction in workload was particularly pronounced in Europe, with a 50% drop in hours worked between 1870 and 2000 (and even 60% in some countries such as Germany or Holland). Among the factors responsible for this trend is the importance of the workers’ movements, whose demands made it possible to limit the excesses and abuses that were frequent at the beginning of the Industrial Revolution (10 to 16 hours of work per day, 6 days a week) and to reduce the work week to a maximum of 40 hours.

Figure 1. Decrease in the number of hours worked annually between 1870 and 2000 in Canada (red) and Europe (black). Adapted from Huberman and Minns (2007).

This reduction in workload, however, does not affect all workers: in some countries, there is a significant proportion of people who still work a lot (more than 50 hours per week), a situation that affects more than one in five workers in Turkey, Mexico, Japan and Korea (Figure 2). In Western countries (United Kingdom and the United States) as well as in Australia, long hours at work are also quite frequent (about 15% of workers), while this phenomenon is much less common in Canada as well as in European countries.

Figure 2. Comparison of the proportion of employees who worked more than 50 hours per week in 2016 in different OECD (Organization for Economic Co-operation and Development) countries. From OECD.Stat.

It should also be noted that since the 1990s, deindustrialization and the technological revolution that have affected economically developed countries have fostered the emergence of a new economy, mainly based on services. There are several consequences to this transformation, one of them being that it has become commonplace to work more than 8 hours a day to meet the demands imposed by work. This type of situation is particularly common among high-skilled workers (finance, health, technology, etc.), with more than one in five people routinely working more than 50 hours a week (Figure 3). Lower skilled workers earning lower wages are not spared, however, since many of them have to combine part-time jobs to make ends meet. In other words, even though the majority of people are currently working less than before, there are still two sub-populations of hard workers: highly skilled workers who have to work long hours in exchange for high wages and/or to keep their jobs, and low-skilled, low-wage workers who have to work longer because of their more precarious financial situation.Figure 3. Increase in the proportion of people who work a lot (50 hours a week or more) among highly skilled workers in Western Europe and North America. From Burger (2015).

Effects on cardiovascular health
An immediate consequence of the long hours spent at work is increasing stress levels, a major risk factor for cardiovascular disease. One of the first clues to this comes from the INTERHEART study, where work-related stress was associated with a twice as high risk of coronary heart disease, an increase similar to that observed for well-documented stressors such as divorce or the death of a loved one. This detrimental effect of overwork on health is particularly well documented in Japan. Loyalty, a sense of duty and sacrifice, and respect for the hierarchy occupy a very important place in Japanese culture; as a result, the number of hours spent at work is considered proof of loyalty to the company, and it is therefore very common to work a lot (up to 60 hours or more per week) to please superiors and keep the respect of colleagues. This extreme “dedication” to the company particularly increased in the 1990s because of what has been called the “Lost Decade”, characterized by economic stagnation, lower wages, and greater job insecurity.

During this period, there was a significant increase in mortality caused by overwork, a phenomenon known in Japan as karōshi (karō “overwork” and shi “death”). In most cases, these premature deaths are a consequence of the detrimental influence of long hours worked on the cardiovascular system: for example, an analysis of the causes of death of 203 karōshi victims revealed that 60% had died of a stroke (meningeal or intracerebral haemorrhage and cerebral infarction), 25% had acute heart failure, 13% had a heart attack, and 2% had an aortic rupture. In addition to these sudden cardiac deaths, it should be noted that overwork is also an important cause of suicide (karōjisatsu), which can account for up to 12% of voluntary deaths in Japan. Similar effects of overwork were observed in other Asian countries, including South Korea (gwarosa) and China (guolaosi); in the latter case, it has become common for Chinese companies to introduce what is familiarly known as “996”, that is, a work schedule from 9 a.m. to 9 p.m., 6 days a week.

In Western countries, a meta-analysis of studies of 600,000 workers in Europe, Australia and the United States showed a strong association between long hours worked and the risk of cardiovascular disease. This analysis revealed that people who work a lot (more than 55 hours per week) are about 13% more likely to have a heart attack than those who work 35–40 hours a week, while the risk of stroke was increased by 33%. This increased risk of stroke, already observed among people who work 41–48 hours (10%), increases to 27% among those who work 49–54 hours, and finally reaches 33% among very hard workers (55 hours and more).

Several psychosocial, behavioural and biological factors have been proposed to explain how stress may contribute to the increased risk of cardiovascular events seen in hard workers (Table 1). However, it should be noted that a link between excessive work and these different factors has not been observed in all studies and their exact contribution remains to be clearly established.

Table 1. Major factors that may contribute to the increased risk of cardiovascular disease caused by overwork.

Factors  Description
Risk behaviours (smoking, excess alcohol)People who work more than 50 hours per week are more likely to smoke (Artazcoz et al. 2009) and drink excessive amounts of alcohol (Virtanen et al. 2015).
Lack of sleepWorking more than 55 hours per week is associated with an increased risk of not getting enough sleep (twice), having difficulty falling asleep (4 times), and fatigue when waking up (twice). (Virtanen et al. 2009).
HypertensionPeople who work more than 50 hours per week are 30% more likely to have high blood pressure (Yang et al. 2006).
Sedentary lifestyleThe high number of hours spent at work reduces the time available for other activities, including exercise. Studies show that physical inactivity, combined with sedentary work, increases the risk of cardiovascular disease (Ekelund et al. 2016).
Fatigue and exhaustionYoung men (<55 years) who had an acute myocardial infarction frequently report episodes of excessive fatigue and exhaustion in the period prior to the coronary heart event (Sihm et al. 1991).
Job strainJob strain, a situation where the worker faces high demands but lacks the resources to meet them, is associated with a 23% increase in the risk of coronary heart disease (Kivimäki et al. 2012) and a 30% increase in the risk of stroke (Huang et al. 2015)
Atrial fibrillationPeople who work long hours are at higher risk for episodes of atrial fibrillation, a major risk factor for stroke (Kivimäki et al. (2017).

The increased risk of atrial fibrillation caused by long working hours is particularly interesting because this arrhythmia causes clots in the left atrium, which can reach the brain and obstruct blood flow to the brain, and could contribute to the increased risk of stroke in people who work hard. This increase in the incidence of atrial fibrillation is mainly observed in people who work more than 50 hours a week, and can reach up to 40% of those who work more than 55 hours a week (Figure 4). It should also be noted that overwork has been associated with other coagulation disorders, including deep vein thrombosis (a 68% increase risk), a major cause of pulmonary embolism.

Figure 4. Effect of the number of hours worked on the risk of atrial fibrillation.
From Kivimäki et al. (2017).

Job strain
Another factor that may contribute to the negative effects of overwork is the so-called job strain, a particular form of stress that has been repeatedly associated with cardiovascular health risk situations. According to the model developed by Robert Karasek (see box), this tension at work is defined as a situation where work and psychological demands are high, combined with a lack of available resources to cope with it and a low decision-making latitude. In other words, a situation where workers are required to be highly productive, but without giving them adequate resources or the necessary flexibility. The risk is further aggravated if the employee has low social support (e.g. from co-workers) and/or if the high productivity requirement is not associated with a valuation of the work done (effort-reward imbalance). It goes without saying that working long hours in such an unfavourable environment can only have a negative impact on both physical and mental health.

Job strain   A work situation is always the result of a combination of two factors: 1) A “psychological demand”, that is to say, the demands imposed by the job (amount of work to be done, time constraints, interruptions, contradictory demands, etc.); 2) “job decision latitude”, i.e., the ability to make decisions and be creative, for example by having the opportunity to choose how to do one’s job, to participate in decisions, and to use skills. According to Karasek, the combination of psychological demand and decision latitude makes it possible to define 4 types of work situations (see figure below)The at-risk combination is one in which the psychological demand is high, either because of the amount of work to be done or its difficulty, combined with the depreciation of the workers due to their low participation in the decision-making process.

In conclusion, overwork is associated with a slight but significant increase in the risk of cardiovascular disease, especially stroke. It should be noted, however, that recent studies suggest that the effect of psychological stress on cardiovascular health is more pronounced in people who already have cardiometabolic abnormalities. For example, it has been shown that the association between work strain and risk of premature mortality was higher among those with a history of diabetes, coronary heart disease, or stroke than among those who had not been affected by these conditions. These at-risk individuals generally have several metabolic abnormalities (high blood sugar, inflammation, atherosclerotic plaques) that increase the risk of cardiovascular events following exposure to the effects of work stress (arrhythmia, hypercoagulation, hypertension, etc.). Conversely, people who work hard but who exercise regularly and are in good physical shape do not show any increase in the risk of coronary heart disease. As with the general population, it is therefore important for hard workers to adopt a generally healthy lifestyle (normal weight, plant-rich diet, regular physical activity) to reduce the effects of stress on the risk of cardiovascular events. Working has never killed anyone … who is in good health.


The Blue Zones: Areas where people are living better and longer

The Blue Zones: Areas where people are living better and longer

Updated on March 15, 2019

Life expectancy at birth in Canada in 2015 was 84.1 years for women and 80.2 years for men. It has been steadily rising for half a century: in 1960 life expectancy was 74.1 years for women and 71.1 for men. However, it is far from the exceptional longevity observed in specific areas of our planet where we find a large proportion of centenarians. These regions, named “Blue Zones”, have been identified by two demographers, Gianni Pes and Michel Poulain, and journalist Dan Buettner, author of the article The Secrets of Long Life in National Geographic magazine and the book The Blue Zones.

The five Blue Zones identified in the world.

Sardinia, Italy
By studying the longevity of the inhabitants of Sardinia, an Italian island in the Mediterranean Sea, the demographers Gianni Pes and Michel Poulain and their collaborators have located the areas where morecentenarianslive. These longevity hot spots, or Blue Zones (the researchers initially used a blue marker to delineate these areas on a map), are located in a mountainous area of ​​the island, the Barbagia, which was still difficult to access a few decades ago. This geographical situation discouraged immigration and promoted consanguinity, reducing the diversity of the genetic heritage. In the area of ​​exceptional longevity, in the southeast of the Province of Nuoro, 91 people have become centenarians among the 18,000 people who were born in the region between 1880 and 1900. In one village in particular, Seulo, 20 centenarians were identified between 1996 and 2016. In comparison, according to Statistics Canada, there were 17.4 centenarians per 100,000 inhabitants in Canada in 2011.

The analysis of genes involved in inflammation, cancer and heart disease did not reveal any significant difference that could be related to the exceptional longevity of the Sardinians. Researchers therefore suspect that environmental characteristics, lifestyle and diet are much more important than genetic predispositions for a long and healthy life. Many of these Sardinian centenarians are shepherds or farmers who have been doing a great deal of outdoor physical activity throughout their lives. The Sardinian diet, which is part of the Mediterranean diet, could play an important role in the longevity of the inhabitants of this Blue Zone. Indeed, the Sardinian diet consists of homegrown vegetables (mainly beans, tomatoes, eggplants), whole-grain bread, Pecorino cheese made from whole milk from grass-fed sheep, and local red wine particularly rich in polyphenols. The traditional Sardinian diet included meat once a week at most.

When journalist Dan Buettner asked some of these centenarians the reason for their exceptional longevity, many mentioned the importance of family and social ties; in Sardinia, elderly people live with their family rather than in retirement homes. The elderly who live in the Sardinian Blue Zone believe they have excellent mental well-being and report few symptoms of depression. An Italian study of 160 elders of the Sardinian Blue Zone reports that the trait of resilience was significantly associated with markers of good mental health. For these seniors, resilience and satisfaction derived from social ties are predictors of all markers of good mental health.

Okinawa, Japan
Japan has one of the largest concentrations of centenarians in the world, more than 34.7 per 100,000 inhabitants in 2010. The inhabitants of the islands of the Okinawa archipelago in southwestern Japan have a particularly high life expectancy, and 66.7 centenarians per 100,000 inhabitants have been recorded in this prefecture. Women living in Okinawa are 3 times more likely to live to age 100 than North Americans. The Okinawa diet is plant-based, and includes many leafy green vegetables, sweet potatoes, fish and seafood. The majority of Okinawa’s centenarians maintained a vegetable garden during their lifetime and moderate physical activity, which helps reduce stress and stay in shape. The people of Okinawa traditionally practice self-restraint when it comes to food, by following the Confucian teaching hara hachi bu, which recommends eating so as to be 80% satiated at the end of a meal. Older people in Okinawa are very active and maintain strong family and social ties, for example through regular meetings called moai. It is very important for them to make sense of their life. To have an ikigaiis to have a reason to get up every morning.

Nicoya, Costa Rica
Life expectancy is relatively high in Costa Rica (82.1 for women and 77.4 for men), especially in the region of the Nicoya Peninsula where men aged 60 are 7 times more likely to become centenarians than other Costa Ricans. Like Sardinia, Nicoya is a region that has been relatively isolated for hundreds of years. The cancer mortality rate is 23% lower than in the rest of the country, and Nicoya residents have a plant-based diet (squash, black beans, corn tortillas, plenty of local fruits), but that also includes eggs and meat (chicken and pork). The centenarians of Nicoya are very physically active, have strong family ties as well as strong religious faith, and like to work. Their stress level is low and they are generally very positive and happy.

Loma Linda, United States
The only identified Blue Zone in North America is located in Loma Linda, a city in Southern California, located 100 km east of Los Angeles, where there is a community of 9,000 members of the Seventh-day Adventist Church. In California, a 30-year-old Adventist man will live on average 7.3 years longer than a white Californian of the same age. A 30-year-old Adventist woman will live on average 4.4 years longer than a Californian of the same age. Knowing that about two thirds of Americans die from cardiovascular disease or cancer, it is not surprising that Adventists are living longer as their way of life means they are less at risk of developing these diseases. About half of Adventists are vegetarians or rarely eat meat, and non-vegetarian Adventists are twice as likely to develop cardiovascular disease. The majority of Adventists are non-smokers and do not drink alcohol. As a result, they have a lower incidence of lung cancer than Americans in general. Adventists are physically active and have a very developed community spirit, as they are very religious and their church encourages its members to help one another.

Icaria, Greece
Icaria is a Greek island in the Eastern Aegean Sea where one in three inhabitants will reach the age of 90. The incidence of cancer, cardiovascular disease, diabetes and dementia is significantly lower than the rest of the world. As in Sardinia, Okinawa and other Blue Zones, Icarians maintain a vegetable garden at home and lead a low-stress life. Their diet, of the Mediterranean type, is composed of vegetables (potatoes, peas, lentils, green leafy vegetables), fruits, olive oil, fish, goat milk, dairy products, and a little meat. Icarians eat little sugar and drink coffee, red wine and herbal teas made from rosemary, sage, oregano and artemisia daily. Icarians who observe the calendar of the Greek Orthodox Church must fast regularly, and caloric restriction is known to slow down the aging process in mammals.

The inhabitants of the Blue Zones, Okinawa, Sardinia, Nicoya, Icaria and Loma Linda, share characteristics in their lifestyle that contribute to their longevity. In his book The Blue Zones, Dan Buettner lists 9 common features:

    • Moderate and regular physical activity, throughout life.
    • Caloric restriction.
    • Semi-vegetarianism, food largely sourced from plants.
    • Moderate alcohol consumption (especially red wine).
    • Give meaning and purpose to life.
    • Reduced stress.
    • Engagement in spirituality or religion.
    • Family is at the centre of life.
    • Social commitment, integration in the community.
The effects of stress on the heart

The effects of stress on the heart

Updated May 22, 2018

In animals, detecting a threat (smell of smoke, sight of a predator, sound of a gunshot) by the sensory organs (nose, eyes, ears) triggers a maximum alert in the brain that will initiate a series of extremely complex processes called the “fight-or-flight response.” By activating the adrenal glands, the brain controls the release of action hormones such as adrenaline into the blood in order to increase the respiratory rate, the heartbeat, the oxygen supply to the tissues, as well as the level of wakefulness and cerebral attention. All these changes are triggered so the animal can quickly fight or flee the danger. This is biological stress, essential to the survival of individuals and, consequently, of their species. Depending on the duration of the metabolic reactions, three categories of effects can be distinguished: 1) the immediate effects caused by the production of adrenaline and norepinephrine by the sympathetic nervous system (duration of a few seconds); 2) the intermediate effects from the secretion of adrenaline and norepinephrine by the medulla of the adrenal glands (duration of a few minutes); and 3) the prolonged effects caused by the hypothalamic-pituitary-adrenal (or corticotropic) axis, vasopressin and thyroxine (duration of a few hours, up to weeks).

Corticotropic axis
When a stressful situation occurs, neuronal signals are produced in the brain by the limbic system (amygdala, hippocampus) and transmitted to the hypothalamus (see Figure 1).

Figure 1. Corticotropic axis. Adapted from Managing stress:
Principles and Strategies for Health and Well-being, Fifth edition, 2005.

In response to this signal, the hypothalamus secretes the corticotropin-releasing hormone (CRH) that activates the pituitary gland, an endocrine gland that secretes several hormones including adrenocorticotropin (ACTH). This hormone is rapidly recognized by specific receptors present in the adrenal glands, which triggers the secretion of corticosteroids (cortisol, aldosterone) and adrenaline. The stress response is relayed by these messengers, which has the effect of increasing metabolism (more energy sources) and blood pressure. Cortisol increases blood pressure and blood sugar levels and inhibits the immune system. Catecholamines (adrenaline and norepinephrine) facilitate the fast and powerful use of muscles. Adrenaline binds to liver cell receptors and stimulates glucose production. Cortisol also induces the transformation of fatty acids into sugars and gluconeogenesis (glucose production from glycogen), which allows a significant energy supply to the muscles in order to escape or fight the stress-generating situation.

Effects of intense stress on the heart
Intense stress has a very important effect on the sympathetic autonomic nervous system that, along with hormones such as adrenaline, directly stimulates the heart. These changes accelerate the heart rate, cause severe cardiac arrhythmias, and may cause coronary arteries to contract. A good example of the negative impact of stress is the dramatic rise in sudden death that follows a tragic event: in the weeks following the earthquake off Sendai and the powerful tsunami that devastated this northeastern region of Japan in 2011, the number of people who died suddenly doubled compared to previous years, a trend that was maintained within three weeks of the initial shock (Figure 2). An increase in sudden mortality has also been observed following other major earthquakes (see here and here), illustrating how the physiological response to acute stress can have a negative impact on the heart.

Figure 2. Increased number of cardiac arrests during the Great East Japan Earthquake in 2011, in the three most affected prefectures (Iwate, Miyagi, Fukushima). Source: Kitamura et al. (2013).

Broken heart syndrome or takotsubo cardiomyopathy
People who do not have coronary heart disease but who are subjected to intense emotional stress may suffer from syndromes known by various names: broken heart syndrome, takotsubo cardiomyopathy, transient left ventricular apical ballooning syndrome, myocardial stunning, and neurogenic stress cardiomyopathy. These syndromes, which have common pathophysiological characteristics, are grouped together under the term “stress-induced cardiomyopathies.” Stress-induced cardiomyopathies without neurological impairment mainly affect women (80–90% of patients), especially postmenopausal women. In most cases, emotional or physical stress occurred before the onset of symptoms. Originally described in 1990 by Japanese cardiologists, takotsubo syndrome occurs when a person is exposed to significant stress or very bad news and suddenly develops high-intensity chest pain, secondary to myocardial infarction. If the person survives (which is usually the case), acute myocardial infarction is noted on arrival at the hospital, but without any arterial injury, i.e., without any blockage of the coronary artery. The name takotsubo comes from the shape of the left ventricle during the angiography exam (Figure 3), which is shaped like a vase (壺, tsubo) that resembles a trap that Japanese fishermen use to catch octopuses (蛸, tako). This phenomenon is caused by severe damage to the left ventricle, which is the region of the heart muscle that pumps arterial blood to the body. Several triggers have been identified over the years, most of them associated with strong negative emotions such as grief, anger or fear. Recent results, however, indicate that strong positive emotions (marriage, victory of a sports team) can also cause the onset of this syndrome.

Figure 3. Left illustration: Angiographic imaging of a heart of a person suffering from a takotsubo.
Right image: The octopus trap (takotsubo) used by fishermen in Japan.


Chronic stress
Aside from these rather extraordinary examples that demonstrate the dramatic effects that the brain and our emotions may have on the heart, thousands of studies have been published on the effect of chronic stress, negative emotions, anxiety, depression, anger and hostility on the incidence of long-term coronary heart disease. In the 1940s and 1950s, early psychosomaticists, namely psychiatrists (usually psychoanalysts), became interested in the psychological characteristics that appeared to be associated with patients with coronary artery disease. Subsequently, in the 1960s, two cardiologists, R. H. Rosenman and Meyer Friedman, described the Type A personality, referring to people who are always in a hurry, are impatient, and have difficulty managing their aggressiveness. Having this type of personality seemed linked to the onset of coronary heart disease, but this link is still quite controversial today. Research on the subject suggests that it is rather two components present in Type A personalities, anger and hostility, that constitute important risk factors. Indeed, a meta-analysis of 25 studies has shown that both of these emotions are associated with a higher risk of having a myocardial infarction. They are also linked to a greater risk of recurrence according to 19 studies in patients who have already suffered a cardiac event.

Despite extensive evidence of a strong link between the brain and cardiovascular disease, this issue has been relatively under the radar of cardiologists until the publication of the Canadian cardiologist Salim Yusuf’s INTERHEART study. This major study, conducted among more than 24,000 people in 52 different countries, aimed to determine the main risk factors for myocardial infarction. Originally, Dr. Yusuf’s primary focus was on the classic risk factors of cholesterol, hypertension, abdominal obesity, and tobacco, but he decided to also observe measures of perceived or objective stress in the patients, even though he wasn’t convinced of its effects. A relevant addition, as the study demonstrated that “psychosocial” stress is indeed associated with an increased risk of myocardial infarction and that this effect, although less important than smoking, is comparable to the effect of hypertension and abdominal obesity. Dr. Yusuf concluded his article by emphasizing that psychosocial factors are far more important than previously recognized, and that they can contribute to a “substantial” proportion of myocardial infarction in all societies. Several mechanisms can explain the effect of stress on the cardiovascular system and, in particular, the coronary arteries: inflammation, increase in blood coagulability, decrease in fibrinolysis (ability of blood to dissolve clots), and increased circulating catecholamines (adrenaline and norepinephrine hormones), which, among other effects, accelerate the heart and increase its force of contraction (Figure 4).

Figure 4. The pathophysiological effects of acute psychosocial stress.
Source: Piña et al., J. Am. Coll. Cardiol. 2018.

Depression and cardiovascular disease
With respect to depression, several studies report that a depressive state after myocardial infarction increases the risk of death in the months following discharge from hospital. A study conducted at the Montreal Heart Institute by Dr. François Lespérance and his collaborators has shown that the presence of depression in hospitalized patients after an unstable angina episode increases the risk of fatal recurrence or infarction by 6 the year following hospital discharge.

Although stress and depression are now recognized as major risk factors for cardiovascular disease, studies on the treatment for these conditions using antidepressant or anxiolytic medications have not produced convincing results. This is a significant problem as up to 30–40% of patients experience depressive symptoms after myocardial infarction, which can greatly increase the risk of recurrence and premature death if not adequately treated. There is also a high rate of depression after cardiac surgery. At the Montreal Heart Institute’s EPIC Centre, for the past 30 years we have observed that a cardiac rehabilitation program that includes exercise training practiced two to three times a week at the Centre, alongside a group of patients with similar conditions, considerably improves depressive feelings and reduces stress after a cardiac event or surgery. When patients are asked what is most important to them after myocardial infarction, many of them say they would like to “reduce their stress.” Patients are also often convinced that the stress they are experiencing is the primary cause of their heart condition.

To successfully prevent recurrence, everything must therefore begin with the brain, because when stress and depressive states are well “managed” and priorities have been redefined, patients are prepared to significantly change their lifestyle habits. Unfortunately, patients from a low socioeconomic background have problems that medicine alone cannot remedy; they benefit the least from prevention programs, for many economic and social reasons. This situation is well documented in western countries. Indeed, poverty remains the biggest risk factor for premature death.

Stress management
How can you change your lifestyle habits when your psychological state is unstable? Based on my experience, the patients with the best outcomes are those who succeed in making quite drastic changes, either by themselves, because the heart attack or cardiac surgery has triggered a reassessment of their personal situation, or with the help of a multidisciplinary team and a stress management program.

Managing your stress — A few references

At the MHI’s EPIC Centre, workshops on stress management through mindfulness are led by Dr. Robert Béliveau and other professionals experienced in this approach. I encourage readers to look into this subject, especially by consulting the following books:

—Christophe André, Looking at Mindfulness;

—Matthieu Ricard, The Art of Meditation;

—Jon Kabat-Zinn, Full Catastrophe Living;

—Rick Hanson, Hardwiring Happiness.

For about ten years, we have been using the approach developed by Jon Kabat-Zinn of the Center for Mindfulness in the Faculty of Medicine at the University of Massachusetts in Boston, an approach called “mindfulness-based stress reduction.” This is a fairly intensive approach presented in eight two-and-a-half-hour-long weekly workshops. This method has proven its value for over 25 years, and many scientific articles have demonstrated its effectiveness, not only for reducing stress and improving overall quality of life but also for preventing recurrence after a cardiac event. For example, a study published in 2012 by R. H. Schneider and his colleagues confirms that practicing meditation for 20 minutes twice a day cuts relapses after a cardiac event in half in the five years following. By managing their stress much better, patients more easily adopt all the changes needed to avoid recurrence.

Should this approach also be used in primary prevention, before becoming ill? The answer is yes, absolutely. People with many risk factors or who have a mediocre quality of life owing to chronic stress can benefit greatly from the mindfulness-based approach.

What the neurosciences have taught us, and what Rick Hanson describes very well in his book Hardwiring Happiness (2013), is that the human brain first went through a “reptilian” stage during evolution, originally reinforcing our reactions to danger to give us a chance at survival. Obviously, the brain evolved and became much more complex with the development of the cerebral cortex, but traces of our reptilian brain are still there. We therefore have a tendency to view negative events as being three to five times more important than positive ones (see here and here). For example, Daniel Kahneman, who received the Nobel Prize in Economics in 2002 for his studies on this subject, observed that, given an equal amount of money, a financial loss is much more strongly felt than a gain. In other words, if you lose $1,000 on the stock market, the psychological impact will be as powerful as if you had won $5,000. The same holds true for our interpersonal relationships: a negative remark or behaviour directed at us has three to five times more impact than its positive equivalent. This tendency to overemphasize the negative has enabled humans to survive and evolve. For example, worrying and then making sure that there are no snakes hidden in a bush is a situation where the vigilance associated with worry results in avoiding a bite, whereas unconcern in the face of danger can cause death. Our brain is thus programmed to worry. To manage our stress well and improve our quality of life, we have to work actively at “reprogramming” it, so it gives more weight to the effects of positive experiences rather than of negative ones.

The approach suggested by Jon Kabat-Zinn, Christophe André, and Matthieu Ricard teaches us to take a moment to pause, carefully observe our physical and psychological reactions, and modify our perceptions and behaviours. Contrary to what many people think, meditation is not a relaxation technique, nor a way to hide our problems. Quite the opposite: the goal is to pause briefly, concentrate on the present moment, and observe our thoughts so as to transform the way we think. It is not a means of relaxation, but rather a means of transformation.

Social isolation: An important risk factor for premature death

Social isolation: An important risk factor for premature death

Several studies have clearly shown that some psychological factors, such as stress anxiety, depression and the lack of adequate social relationships, have a negative impact on health and significantly reduce life expectancy. This close relationship between psychology and physiology is particularly well documented with regard to social relationships. Indeed, a large number of studies have shown that people who are more socially engaged are in overall better health and have a decreased risk of depression and a reduced rate of cognitive decline. Conversely, social isolation and solitude (see box below for the distinction between the two) increase the risk of premature death, an impact comparable to that of well-established risk factors such as obesity, physical inactivity, and even tobacco use.  For example, the data collected during studies conducted among a total of 308,849 subjects indicated that those who have adequate social relationships have a 50% lower risk of premature mortality compared to those who have unsatisfying social relationships, an impact comparable to smoking cessation. These results are in line with the data collected during the Harvard Study of Adult Development, which has been studying the factors involved in healthy aging, from both the physical and psychological point of view, since 1939. The main conclusion of this study, which has been ongoing for 75 years, is simple: quality personal relationships, whether with family or friends, are one of the most important predictive factors of a person’s happiness and good health throughout their life.

Social isolation and solitude: two distinct realities
Social isolation refers to a lack of interpersonal relationships. It is an objective parameter that can be measured by examining whether a person lives alone, their conjugal status, the size of their social network, and their participation in group activities. Social isolation is a particularly frequent problem in elderly people, when a decrease in economic resources, invalidity, or the death of family and friends contribute to reducing social contacts. Studies show that socially isolated individuals are at greater risk of heart diseaseinfectious diseases (such as colds), cognitive decline, and premature mortality. These increased risks are a result of the negative impact of social isolation on several physiological parameters, in particular an increase in blood pressure and fibrinogen levels (higher risk of developing blood clots) as well as the activation of inflammatory processes.

As for solitude, it can be viewed as the psychological counterpart of social isolation, i.e., it is not only the number of contacts that come into play, but mainly dissatisfaction regarding the quality of the social relationships a person maintains (frequency, intimacy). Thus, a person can suffer from solitude even when surrounded by people, and, conversely, someone can feel not alone even if they live in an isolated way. Studies show that solitude is associated with a disruption of several physiological processes, including increased blood pressurecortisol levels in the blood and inflammatory processes, as well as a higher risk of heart disease and premature mortality.

One of the main health problems resulting from social isolation and solitude is the increased risk of heart disease.  Epidemiological studies show that low social support is associated with an approximately two-fold increase of the risk of cardiovascular events and is a predictive factor for hypertensioncoronary heart disease and heart failure. In patients who have already suffered a myocardial infarction, studies show that low emotional and social support triples the risk of cardiovascular events and mortality, impacts comparable to those of other well-documented risk factors such as hypercholesterolemia, type 2 diabetes, and tobacco use.

Two main reasons explain this enormous influence of the social network on the risk of heart disease. First, social relationships can act as “stress buffers” that alleviate the negative impacts associated with difficult times in life (disease, bereavement, divorce, etc.). An adequate social network can offer structural and emotional support to the people affected by these ordeals, helping them better deal with the shock, and thus reducing the harmful physiological consequences resulting from chronic stress, in particular on the risk of heart disease.  Studies also show that individuals with a developed social network tend to be more physically active and adopt better lifestyle habits, which contributes to reducing the risk of heart disease and improving life expectancy. Socially active people are also more likely to receive better advice from their family and friends in the event of health problems and to quickly consult following an anomaly (chest pain, for example). Isolated people cannot count on this type of support due to the absence of someone they can trust in their circle, which contributes to a higher rate of premature death, in particular in those who present certain risk factors for heart disease.

However, the impact of the social network is not only psychological: it is now clearly proven that isolation is perceived by the body as a form of “aggression” and provokes the activation of physiological mechanisms involved in the stress response, such as the secretion of cortisol and adrenaline. For example, studies show that inadequate social relationships are associated with an increase in adrenaline levels in urine, a higher resting heart rate and an exaggerated increase in blood pressure and heart rate in response to stress, followed by a slower recovery. Socially isolated individuals are also more at risk of presenting lower heart rate variability (the interval between two heartbeats) and left ventricular hypertrophy, two risk factors of cardiovascular mortality.  Over time, all these effects of chronic stress damage the heart and blood vessels and would explain the marked increase in cardiovascular events observed in socially isolated people.

Studies suggest that social isolation could also foster the development of atherosclerosis, the process responsible for the formation of plaque on the artery walls. Studies conducted in the 50s on animals at the Philadelphia zoo showed that isolation of birds and mammals was associated with a ten-fold increase of atherosclerotic lesions in these animals. In humans, a study showed that some markers of a diminished social network (widowhood, celibacy) were associated with an increase of the degree of coronary artery calcification, a marker of atherosclerosis. It was also observed that low social support, combined with a tendency toward anger, greatly accelerates the progression of atherosclerosis plaques, which could contribute to a higher risk of cardiovascular events observed in people exhibiting hostile behaviour.

When we discuss the prevention of heart disease, what generally comes to mind is the importance of quitting smoking, adopting a healthy diet high in plant-based foods, exercising regularly, and maintaining a healthy body weight. These lifestyle changes are of course crucial, but the disastrous impact of inadequate social relationships on the risk of developing and dying from these diseases is a reminder that we cannot overlook the importance of psychosocial factors in any strategy intended to reduce their incidence. Especially since several current trends such as the aging of the population, high divorce rates, and the increasing number of people living alone (in Quebec, 1 out of 3 households were one person in 2011) can exacerbate social isolation and the feeling of solitude. The impending mass retirement of baby-boomers is another factor to consider, since several new retirees see their health rapidly decline following their departure from the workplace.  However, studies show that this risk can be considerably reduced by replacing the loss of work relationships by joining other groups (sports, cultural, political or other).  Several people turn to social media, in particular Facebook, to maintain a network of contacts, and a recent study suggests that this “virtual” social life can provide the same benefits as a “real” social life in terms of reducing the risk of premature death. Whatever shape it takes, it is certain that a dynamic, diversified social network is a major asset to living longer in good health and should be a basic element of life hygiene.  Indeed, in all the regions of the world recognized for the longevity of their inhabitants (Blue Zones), establishing a close-knit social fabric is part of the “secret” to a long life, on par with a healthy diet, regular physical activity, moderate alcohol consumption, and stress management.