Why do the Japanese have the highest life expectancy in the world?

Why do the Japanese have the highest life expectancy in the world?

OVERVIEW

  • The Japanese have the highest life expectancy at birth among the G7 countries.
  • The higher life expectancy of the Japanese is mainly due to fewer deaths from ischemic heart disease, including myocardial infarction, and cancer (especially breast and prostate).
  • This exceptional longevity is explained by a low rate of obesity and a unique diet, characterized by a low consumption of red meat and a high consumption of fish and plant foods such as soybeans and tea.

Several diets are conducive to the maintenance of good health and to the prevention of cardiovascular disease, for example, the Mediterranean diet, the DASH diet (Dietary Approaches to Stop Hypertension), the vegetarian diet, and the Japanese diet. We often refer to the Mediterranean Diet in these pages, because it is well established scientifically that this diet is particularly beneficial for cardiovascular health. Knowing that the Japanese have the highest life expectancy among the G7 countries, the special diet in Japan has also captured the attention of experts and an informed public in recent years.

Japanese life expectancy
Among the G7 countries, Japan has the highest life expectancy at birth according to 2016 OECD data, particularly for women. Japanese men have a slightly higher life expectancy (81.1 years) than that of Canadian men (80.9 years), while the life expectancy of Japanese women (87.1 years) is significantly higher (2.4 years) than that of Canadian women (84.7 years). The healthy life expectancy of the Japanese, 74.8 years, is also higher than in Canada (73.2 years).

The higher life expectancy of Japanese people is mainly due to fewer deaths from ischemic heart disease and cancers, particularly breast and prostate cancer. This low mortality is mainly attributable to a low rate of obesity, low consumption of red meat, and high consumption of fish and plant foods such as soybeans and tea. In Japan, the obesity rate is low (4.8% for men and 3.7% for women). By comparison, in Canada 24.6% of adult men and 26.2% of adult women were obese (BMI ≥ 30) in 2016. Obesity is an important risk factor for both ischemic heart disease and several types of cancers.

Yet in the early 1960s, Japanese life expectancy was the lowest of any G7 country, mainly due to high mortality from cerebrovascular disease and stomach cancer. The decrease in salt and salty food intake is partly responsible for the decrease in mortality from cerebrovascular disease and stomach cancer. The Japanese consumed an average of 14.5 g of salt/day in 1973 and probably more before that. They eat less salt these days (9.5 g/day in 2017), but it’s still too much. Canadians now consume on average about 7 g of salt/day (2.76 g of sodium/day), almost double the intake recommended by Health Canada.

The Japanese diet
Compared to Canadians, the French, Italians and Americans, the Japanese consume much less meat (especially beef), dairy products, sugar and sweeteners, fruits and potatoes, but much more fish and seafood, rice, soybeans and tea (Table 1). In 2017, the Japanese consumed an average of 2,697 kilocalories per day according to the FAO, significantly less than in Canada (3492 kcal per day), France (3558 kcal per day), Italy (3522 kcal per day), and the United States (3766 kcal per day).

Table 1. Food supply quantity (kg/capita/year) in selected countries in 2013a.

              aAdapted from Tsugane, 2020. FAO data: FAOSTAT (Food and agriculture data) (http://www.fao.org/).

Less red meat, more fish and seafood
The Japanese eat on average almost half as much meat as Canadians (46% less), but twice as much fish and seafood. This considerable difference translates into a reduced dietary intake of saturated fatty acids, which is associated with a lower risk of ischemic heart disease, but an increased risk of stroke. On the contrary, dietary intake of omega-3 fatty acids found in fish and seafood is associated with a reduced risk of ischemic heart disease. The lower consumption of red meat and higher consumption of fish and seafood by the Japanese could therefore explain the lower mortality from ischemic heart disease and the higher mortality from cerebrovascular disease in Japan. Experts believe that the decline in death from cerebrovascular disease is associated with changes in the Japanese diet, specifically increased consumption of animal products and dairy products, and consequently of saturated fat and calcium (a consumption which remains moderate), combined with a decrease in salt consumption. Indeed, contrary to what is observed in the West, the consumption of saturated fat in Japan is associated with a reduction in the risk of hemorrhagic stroke and to a lesser extent of ischemic stroke, according to a meta-analysis of prospective studies. The cause of this difference is not known, but it could be attributable to genetic susceptibility or confounding factors according to the authors of the meta-analysis.

Soybeans
Soy is a food mainly consumed in Asia, including Japan where it is consumed as is after cooking (edamame) and especially in processed form, by fermentation (soy sauce, miso paste, nattō) or by coagulation of soy milk (tofu). It is an important source of isoflavones, molecules that have anticancer properties and are beneficial for good cardiovascular health. Consumption of isoflavones by Asians has been linked to a lower risk of breast and prostate cancer (see our article on the subject).

Sugar
The Japanese consume relatively few sugars and starches, which partly explains the low prevalence of obesity-associated diseases such as ischemic heart disease and breast cancer.

Green tea
The Japanese generally consume green tea with no added sugar. Prospective studies from Japan show that green tea consumption is associated with a lower risk of all-cause mortality and cardiac death.

Westernization of Japanese eating habits
The westernization of the Japanese diet after World War II allowed the inhabitants of this country to be healthier and to reduce mortality caused by infectious diseases, pneumonia and cerebrovascular diseases, thereby considerably increasing their life expectancy. A survey of the eating habits of 88,527 Japanese from 2003 to 2015 indicates that this westernization continues. Based on the daily consumption of 31 food groups, the researchers identified three main types of eating habits:

1- Plant foods and fish
High intakes of vegetables, fruits, legumes, potatoes, mushrooms, seaweed, pickled vegetables, rice, fish, sugar, salt-based seasonings and tea.

2- Bread and dairy
High intakes of bread, dairy products, fruits and sugar. Low intake of rice.

3- Animal foods and oils
High intakes of red and processed meat, eggs, vegetable oils.

A downward trend in the “plant foods and fish” group (the staple of the traditional Japanese diet or washoku) was observed in all age groups. An increase in the “bread and dairy” group was observed in the 50–64 and ≥65 years age groups, but not among the youngest. For the “animal foods and oils” group, an increasing trend was observed during the thirteen years of the study in all age groups except the youngest (20–34 years). The Japanese are eating more and more like Westerners. Will this have an adverse effect on their health and life expectancy? It is too early to know, only the next few decades will tell.

Contribution of genes and lifestyle to the health of the Japanese
Some risk factors for cardiovascular disease and cancer are hereditary, while others are associated with lifestyle (diet, smoking, exercise, etc.). At the turn of the 20th century, there was significant Japanese immigration to the United States (especially California and Hawaii) and South America (Brazil, Peru). After a few generations, the descendants of Japanese migrants adopted the way of life of the host countries. While Japan has one of the lowest incidences of cardiovascular disease in the world, this incidence doubled among the Japanese who migrated to Hawaii and quadrupled among those who chose to live in California according to a 1975 study. What is surprising is that this increase has been observed regardless of blood pressure or cholesterol levels, and seems rather directly related to the abandonment of the traditional Japanese way of life by migrants.

Since the 1970s, the average cholesterol level of the Japanese has nonetheless increased, but despite this and the high rate of smoking in this country, the incidence of coronary heart disease remains substantially lower in Japan than in the West. To better understand these differences, a 2003 study compared the risk factors and diets of Japanese living in Japan with third- and fourth-generation Japanese migrants living in Hawaii in the United States. Men’s blood pressure was significantly higher among Japanese than among Japanese-Americans, while there was no significant difference for women. Far fewer Japanese were treated for hypertension than in Hawaii. More Japanese people (especially men) smoked than Japanese-Americans. Body mass index, blood levels of LDL cholesterol, total cholesterol, glycated hemoglobin (an indicator for diabetes), and fibrinogen (a marker of inflammation) were significantly lower in Japan than in Hawaii. HDL cholesterol (the “good” cholesterol) was higher in the Japanese than in the Japanese-Americans. The dietary intake of total fat and saturated fatty acids (harmful to cardiovascular health) was lower in Japan than in Hawaii. In contrast, the intake of polyunsaturated fatty acids and omega-3 fatty acids (beneficial for good cardiovascular health) was higher in Japan than in Hawaii. These differences may partly explain the lower incidence of coronary heart disease in Japan than in Western industrialized countries.

In other words, even if these migrants have the same basic risk as their compatriots who have remained in the country of origin (age, sex and heredity), the simple fact of adopting the lifestyle of their host country is enough to significantly increase their risk of cardiovascular disease.

Although the Japanese diet is different from those of Western countries, it has similar characteristics to the Mediterranean diet. Why not prepare delicious Japanese soy dishes from time to time (for example, tofu, edamame, miso soup), drink green tea, eat less meat, sugar and starch and more fish? Not only will your meals be more varied, but you could enjoy the health benefits of the Japanese diet.

Reducing calorie intake by eating more plants

Reducing calorie intake by eating more plants

OVERVIEW

  • Twenty volunteers were fed a low-fat or low-carbohydrate diet in turn for two weeks.
  • Participants on the low-fat diet consumed an average of nearly 700 fewer calories per day than with the low-carbohydrate diet, a decrease correlated with a greater loss of body fat.
  • Compared to the low-carbohydrate diet, the low-fat diet also led to lower cholesterol levels, reduced chronic inflammation, and lowered heart rate and blood pressure.
  • Overall, these results suggest that a diet mainly composed of plants and low in fat is optimal for cardiovascular health, both for its superiority in reducing calorie intake and for its positive impact on several risk factors for cardiovascular disease.

It is estimated that there are currently around 2 billion overweight people in the world, including 600 million who are obese. These statistics are truly alarming because it is clearly established that excess fat promotes the development of several diseases that decrease healthy life expectancy, including cardiovascular disease, type 2 diabetes, and several types of cancer. Identifying the factors responsible for this high prevalence of overweight and the possible ways to reverse this trend as quickly as possible is therefore essential to improve the health of the population and avoid unsustainable pressures on public health systems in the near future.

Energy imbalance
The root cause of overweight, and obesity in particular, is a calorie intake that exceeds the body’s energy needs. To lose weight, therefore, it is essentially a matter of restoring the balance between the calories ingested and the calories expended.

It might seem simple in theory, but in practice most people find it extremely difficult to lose weight. On the one hand, it is much easier to gain weight than to lose weight. During evolution, we have had to deal with periods of prolonged food shortages (and even starvation, in some cases) and our metabolism has adapted to these deficiencies by becoming extremely efficient at accumulating and conserving energy in the form of fat. On the other hand, the environment in which we currently live strongly encourages overconsumption of food. We are literally overwhelmed by an endless variety of attractive food products, which are often inexpensive, easily accessible, and promoted by very aggressive marketing that encourages their consumption. The current epidemic of overweight and obesity thus reflects our biological predisposition to accumulate reserves in the form of fat, a predisposition that is exacerbated by the obesogenic environment that surrounds us.

Eating less to restore balance
The body’s innate tendency to keep energy stored in reserve as fat makes it extremely difficult to lose weight by “burning” those excess calories by increasing the level of physical activity. For example, a person who eats a simple piece of sugar pie (400 calories) will have to walk about 6.5 km to completely burn off those calories, which, of course, is difficult to do on a daily basis. This does not mean that exercise is completely useless for weight loss. Research in recent years shows that exercise can specifically target certain fat stores, especially in the abdominal area. Studies also show that regular physical activity is very important for long-term maintenance of the weight lost from a low-calorie diet. However, there is no doubt that it is first and foremost the calories consumed that are the determining factors in weight gain. Moreover, contrary to what one might think, levels of physical activity have hardly changed for the last thirty years in industrialized countries, and the phenomenal increase in the number of overweight people is therefore mainly a consequence of overconsumption of food. Exercise is essential for the prevention of all chronic diseases and for the maintenance of general good health, but its role in weight loss is relatively minor. For overweight people, the only realistic way to lose weight significantly, and especially to maintain these losses over prolonged periods, is thus to reduce calorie intake.

Less sugar or less fat?
How do we get there? First, it’s important to realize that the surge in the number of overweight people has coincided with a greater availability of foods high in sugar or fat (and sometimes both). All countries in the world, without exception, that have adopted this type of diet have seen their overweight rates skyrocket, so it is likely that this change in eating habits plays a major role in the current obesity epidemic.

However, the respective contributions of sugar and fat to this increase in caloric intake and overweight are still the subjectof vigorous debate:

1) On the one hand, it has been proposed that foods high in fat are particularly obesogenic, since fats are twice as high in calories as carbohydrates, are less effective in causing a feeling of satiety, and improve the organoleptic properties of foods, which generally encourages (often unconscious) overconsumption of food. Therefore, the best way to avoid overeating and becoming overweight would be to reduce the total fat intake (especially saturated fat due to its negative impact on LDL-cholesterol levels) and replace it with complex carbohydrates (vegetables, legumes, whole-grain cereals). This is colloquially called the low-fat approach, advocated for example by the Ornish diet.

2) On the other hand, the exact opposite is proposed, i.e. that it would be mainly carbohydrates that would contribute to overconsumption of food and to the increase in the incidence of obesity. According to this model, carbohydrates in foods in the form of free sugars or refined flours cause insulin levels to rise markedly, causing massive energy storage in adipose tissue. As a result, fewer calories remain available in the circulation for use by the rest of the body, causing increased appetite and overeating to compensate for this lack. In other words, it wouldn’t be because we eat too much that we get fat, but rather because we are too fat we eat too much.

3) By preventing excessive fluctuations in insulin levels, a diet low in carbohydrates would thus limit the anabolic effect of this hormone and, therefore, prevent overeating and the accumulation of excess fat.

Less fat on the menu, fewer calories ingested
To compare the impact of low-carb and low-fat diets on calorie intake, Dr. Kevin Hall’s group (NIH) recruited 20 volunteers who were fed each of these diets in turn for two weeks. The strength of this type of cross-study is that each participant consumes both types of diets and that their effects can therefore be compared directly on the same person.

As shown in Figure 1, the two diets studied were completely opposite of each other, with 75% of the calories in the low-fat (LF) diet coming from carbohydrates versus only 10% from fat, while in the low-carb (LC) diet, 75% of calories were in the form of fat, compared to only 10% from carbohydrates. The LF diet under study consisted exclusively of foods of plant origin (fruits, vegetables, legumes, root vegetables, soy products, whole grains, etc.), while the LC diet contained mainly (82%) animal foods (meat, poultry, fish, eggs, dairy products).

Figure 1. Comparison of the amounts of carbohydrates, fats and proteins present in the low-carbohydrate (LC) and low-fat (LF) diets consumed by study participants. Adapted from Hall et al. (2021).

The study shows that there is indeed a big difference between the two types of diets in the number of calories consumed by participants (Figure 2). Over a two-week period, participants who ate an LF (low-fat) diet consumed an average of nearly 700 calories (kcal) per day less than an LC (low-carbohydrate) diet. This difference in calorie intake is observed for all meals, both at breakfast (240 calories less for the LF diet), at lunch (143 calories less), at dinner (195 calories less), and during snacks taken between meals (128 calories less). This decrease is not caused by a difference in the appreciation of the two diets by the participants, as parallel analyses did not find any difference in the level of appetite of the participants, nor in the degree of satiety and satisfaction generated by the consumption of either diet. However, the LF diet was composed exclusively of plant-based foods and therefore much richer in non-digestible fibres (60 g per day compared to only 20 g for the LC diet), which greatly reduce the energy density of meals (quantity of calories per g of food) compared to the high-fat LC diet. It is therefore very likely that this difference in energy density contributes to the lower calorie intake observed for the low-fat diet.

Overall, these results indicate that a diet consisting of plants, and thus low in fat and high in complex carbohydrates, is more effective than a diet consisting mainly of animal products, high in fat and low in carbohydrates, to limit calorie intake.

Figure 2. Comparison of the daily calorie intake of participants on a low-carbohydrate (LC) or low-fat (LF) diet. From Hall et al. (2021).

Weight loss
Despite the significant difference in calorie intake observed between the two diets, their respective impact on short-term weight loss is more nuanced. At first glance, the LC diet appeared to be more effective than the LF diet in causing rapid weight loss, with about 1 kg lost on average in the first week and almost 2 kg after two weeks, compared to only 1 kg after two weeks of the LF diet (Figure 3). However, further analysis revealed that the weight loss caused by the LC diet was mainly in the form of lean mass (protein, water, glycogen), while this diet had no significant impact on fat loss during this period. Conversely, the LF diet had no effect on this lean body mass, but did cause a significant decrease in body fat, to around 1 kg after two weeks. In other words, only the LF diet caused a loss of body fat during the study period, which strongly suggests that the decrease in calorie intake made possible by this type of diet may facilitate the maintenance of astable body weight and could even promote weight loss in overweight people.

Figure 3. Comparison of changes in body weight (top), lean mass (middle), and body fat (bottom) caused by low-carbohydrate and low-fat diets. From Hall et al. (2021).

Cardiovascular risk factors
In addition to promoting lower calorie intake and fat loss, the LF diet also appears to be superior to the LC diet in terms of its impact on several cardiovascular risk factors (Table 1):

Cholesterol. It is well established that LDL cholesterol levels increase in response to a high intake of saturated fat (see our article on the issue). It is therefore not surprising that the LF diet, which contains only 2% of all calories as saturated fat, causes a significant decrease in cholesterol, both in terms of total cholesterol and LDL cholesterol. At first glance, the high-fat LC diet (containing 30% of the daily calorie intake as saturated fat) does not appear to have a major effect on LDL cholesterol; however, it should be noted that this diet significantly modifies the distribution of LDL cholesterol particles, in particular with a significant increase in small and dense LDL particles. Several studies have reported that these small, dense LDL particles infiltrate artery walls more easily and also appear to oxidize more easily, two key events in the development and progression of atherosclerosis. In sum, just two weeks of a high-fat LC diet was enough to significantly (and negatively) alter the atherogenic profile of participants, which may raise doubts about the long-term effects of this type of diet on cardiovascular health.

Table 1. Variations in certain risk factors for cardiovascular disease following a diet low in carbohydrates or low in fat. From Hall et al. (2021).

Branched-chain amino acids. Several recent studies have shown a very clear association between blood levels of branched-chain amino acids (leucine, isoleucine and valine) and an increased risk of metabolic syndrome and type 2 diabetes, two very important risk factors for cardiovascular diseases. In this sense, it is very interesting to note that the levels of these amino acids are almost twice as high after two weeks of the LC diet compared to the LF diet, suggesting a positive effect of a diet rich in plants and poor in fats in the prevention of these disorders.

Inflammation. Chronic inflammation is actively involved in the formation and progression of plaques that form on the lining of the arteries and can lead to the development of cardiovascular events such as myocardial infarction and stroke. Clinically, this level of inflammation is often determined by measuring levels of high-sensitivity C-reactive protein (hsCRP), a protein made by the liver and released into the blood in response to inflammatory conditions. As shown in Table 1, the LF diet significantly decreases the levels of this inflammatory marker, another positive effect that argues in favour of a plant-rich diet for the prevention of cardiovascular disease.

In addition to these laboratory data, the researchers noted that participants who were fed the LF diet had a slower heart rate (73 vs. 77 beats/min) as well as lower blood pressure (112/67 vs. 116/69 mm Hg) than observed following the LC diet. In the latter case, this difference could be related, at least in part, to the much higher sodium consumption in the LC diet compared to the LF diet (5938 vs. 3725 mg/day).

All of these results confirm the superiority of a diet mainly composed of plants on all the factors involved in cardiovascular health, whether in terms of lipid profile, chronic inflammation, or adequate control of calorie intake necessary to maintain body weight.

Electronic cigarettes cause much less inflammation than tobacco

Electronic cigarettes cause much less inflammation than tobacco

OVERVIEW

  • Cigarette smoke causes chronic inflammation that significantly increases the risk of lung and cardiovascular disease.
  • Two recent studies show that this inflammation can be considerably reduced by replacing cigarettes with e-cigarettes.
  • Smokers can therefore drastically reduce the damage caused by cigarette smoke and the risk of smoking-related illnesses by using e-cigarettes as a source of nicotine.

It is now well established that smokers have a reduced life expectancy of around 10 years compared to non-smokers. This dramatic increase in the risk of premature mortality is due to the repeated exposure of smokers to the thousands of toxic and carcinogenic substances that are generated during the combustion of tobacco leaves (polycyclic aromatic hydrocarbons and nitrosamines, among others). For example, it is estimated that each pack of cigarettes contains enough carcinogenic compounds to cause two mutations in the DNA of lung cells, so decades of smoking results in the accumulation of several thousand of these mutations and dramatically increases (about 40 times) the risk of lung cancer.

Pro-inflammatory smoke
Another factor that contributes to the harmfulness of tobacco is the chronic inflammation caused by the many toxic compounds found in cigarette smoke. Locally, this inflammation damages cells in the airways and greatly increases the risk of developing chronic obstructive pulmonary disease (e.g. emphysema). But the damage caused by this inflammation is not limited to the lungs. Following inhalation of cigarette smoke, the toxic compounds rapidly diffuse into the pulmonary capillaries and can then spread throughout the body via the bloodstream. A climate of generalized chronic inflammation is then created, characterized by an increase in several inflammatory markers (IL-6, CRP, ICAM) and the recruitment of immune cells to the surface of blood vessels, two phenomena that contribute to the development of atherosclerosis.

The blood vessels that supply the heart (coronary arteries) are particularly vulnerable to this inflammation. Since the heart is closely associated with the lungs, it is the first organ to receive blood that has been in contact with cigarette smoke and is therefore necessarily exposed to higher concentrations of toxic compounds.

The consequences of this proximity are disastrous. Studies show that people who smoke a pack a day have a 5 times higher risk of myocardial infarction compared to those who have never smoked, and smoking is estimated to be responsible for about 20% of all coronary heart disease deaths. So, even though we mainly talk about the major impact of tobacco on the risk of suffering from lung cancer, we must not forget that cardiovascular diseases remain the main cause of death associated with smoking. Of all the actions a person can take to improve their cardiovascular health (and overall health), quitting smoking is by far the most important.

Reversible damage
The good news is that this damage of smoking on cardiovascular health can be reversed by quitting. Studies show that former smokers see their risk of cardiovascular accident decrease by 40% in the first five years after quitting and becomes similar to that of non-smokers after 10–15 years. Smoking cessation is beneficial at any age, but is particularly effective before the age of 40, with a 90% reduction in the risk of premature death from smoking.

Quitting smoking is difficult, with only 5% of people able to remain smoke-free after one year. However, several recent data show that this smoking cessation success rate can be considerably increased among smokers who opt for e-cigarettes. For example, a randomized clinical trial recently showed that e-cigarettes can double the effectiveness of smoking cessation compared to traditional approaches based on nicotine replacement therapy. A Cochrane review of 50 studies (including 26 randomized trials) with a total of 12,430 participants comes to a similar conclusion.

Reducing damage
In addition to facilitating smoking cessation in the longer term, adopting e-cigarettes also has the advantage of immediately reducing the damage caused by tobacco. Remember that in an e-cigarette, a nicotine solution is heated to 80°C (compared to temperatures around 900°C in a cigarette), and therefore the vapour generated does not contain carbon monoxide, nor the thousands of toxic combustion products found in cigarette smoke. According to a recent study by the Institut Pasteur, the vapour emanating from e-cigarettes contains less than 1% of the toxins present in cigarette smoke, and consequently substantially reduce smokers’ exposure to these toxic compounds (see our article on this subject).

Two recent studies show that this drastic decrease in the amount of toxic compounds in e-cigarette vapour correlates with a significant decrease in inflammation normally observed in response to cigarette smoke. In the first of these studies, the researchers compared the levels of different inflammatory markers (hsCRP, IL-6, sICAM) or oxidative stress (urinary 8-isoprostane) present in non-smokers, vapers, cigarette smokers, and mixed users (vapers and smokers). As shown in Figure 1, while smoking causes a significant increase in the levels of all markers examined, these increases are much smaller, and in some cases (IL-6) even completely abolished, among exclusive e-cigarette users. Replacing tobacco cigarettes with an e-cigarette can therefore substantially decrease the inflammatory response and, in turn, reduce the risk of cardiovascular disease. However, the study clearly shows that this reduction in inflammation is not at all observed in vapers who continue to smoke cigarettes at the same time. To truly reduce the damage caused by smoking, e-cigarettes must therefore completely replace cigarettes and not simply serve to reduce the number of cigarettes smoked in a day.

Figure 1. Change in the levels of different markers of inflammation and oxidative stress in vapers and smokers. From Stokes et al. (2020). hsCRP: high sensitivity C-reactive protein; IL-6: interleukin-6; sICAM: soluble intercellular adhesion molecule.

The other study looked at the impact of e-cigarettes on the expression of inflammatory proteins by monocytes, a class of white blood cells involved in the innate immune response. Over-activation of these cells (by toxic compounds like cigarette smoke, for example) has been shown to trigger an inflammatory response that plays an important role in the initiation and progression of atherosclerosis.

Using blood samples taken from non-smokers, smokers, and vapers, the researchers examined by flow cytometry the profiles of inflammatory proteins (caspase-1, IL-6 receptor, TLR4) present in circulating monocytes in each category of volunteers. Unsurprisingly, they noted that the expression of all of these inflammatory proteins was higher in smokers, about 4 times higher on average than in non-smokers. However, this inflammatory signature was completely absent in vapers, suggesting once again that the elimination of cigarettes in favour of e-cigarettes leads to concrete health benefits for smokers. This is consistent with a recent randomized controlled trial that showed that the transition of smokers to e-cigarettes is accompanied by a rapid improvement (in just 1 month) in the health of the blood vessels.

This study shows once again how e-cigarettes allow smokers to significantly reduce their exposure to the many toxic substances in cigarette smoke and are therefore an extremely useful tool in the fight against diseases caused by smoking.

Effects of cold on cardiovascular health

Effects of cold on cardiovascular health

OVERVIEW

  • Exposure to cold causes a contraction of blood vessels as well as an increase in blood pressure, heart rate, and the work of the heart muscle.
  • The combination of cold and exercise further increases stress on the cardiovascular system.
  • Cold temperatures are associated with increased cardiac symptoms (angina, arrhythmias) and an increased incidence of myocardial infarction and sudden cardiac death.
  • Patients with coronary artery disease should limit exposure to cold and dress warmly and cover their face when exercising.

Can the sometimes biting cold of our winters affect our overall health and our cardiovascular health in particular? For an exhaustive review of the literature on the effects of cold on health in general, see the summary report (in French only) recently published by the Institut national de santé publique du Québec (INSPQ). In this article, we will focus on the main effects of cold on the cardiovascular system and more specifically on the health of people with cardiovascular disease.

Brief and prolonged exposure to cold both affect the cardiovascular system, and exercise in cold weather further increases stress on the heart and arteries. Numerous epidemiological studies have shown that cardiovascular disease and mortality increase when the ambient temperature is cold and during cold spells. The winter season is associated with a greater number of cardiac symptoms (angina, arrhythmias) and cardiovascular events such as hypertensive crisis, deep venous thrombosis, pulmonary embolism, aortic ruptures and dissections, stroke, intracerebral hemorrhage, heart failure, atrial fibrillation, ventricular arrhythmia, angina pectoris, acute myocardial infarction, and sudden cardiac death.

Mortality from cold
Globally, more temperature-related deaths were caused by cold (7.29%) than heat (0.42%). For Canada, 4.46% of deaths were attributable to cold (2.54% for Montreal), and 0.54% to heat (0.68% for Montreal).

Intuition may lead us to believe that it is during periods of extreme cold that more adverse health effects occur, but the reality is quite different. According to a study that analyzed 74,225,200 deaths that occurred between 1985 and 2012 in 13 large countries on 5 continents, extreme temperatures (cold or hot) accounted for only 0.86% of all deaths, while the majority of cold-related deaths occurred at moderately cold temperatures (6.66%).

Acute effects of cold on the cardiovascular system of healthy people

Blood pressure. The drop in skin temperature upon exposure to cold is detected by skin thermoreceptors that stimulate the sympathetic nervous system and induce a vasoconstriction reflex (decrease in the diameter of the blood vessels). This peripheral vasoconstriction prevents heat loss from the surface of the body and has the effect of increasing systolic (5–30 mmHg) and diastolic (5–15 mmHg) blood pressure.

Heart rate. It is not greatly affected by exposure of the body to cold air, but it increases rapidly when, for example, the hand is dipped in ice water (“cold test” used to make certain diagnoses, such as Raynaud’s disease) or when very cold air is inhaled. Cold air usually causes a slight increase in heart rate in the range of 5 to 10 beats per minute.

Risk of atheromatous plaque rupture?
Post-mortem studies have shown that rupture of atheroma plaques (deposits of lipids on the lining of the arteries) is the immediate cause of over 75% of acute myocardial infarctions. Could cold stress promote the rupture of atheromatous plaques? In a laboratory study, mice exposed to cold in a cold room (4°C) for 8 weeks saw their blood LDL cholesterol level and the number of plaques increase compared to mice in the control group (room at 30°C). Furthermore, it is known that exposure to cold induces aggregation of platelets in vitro and increases coagulation factors in vivo in patients during colder days (< 20°C) compared to warmer days (> 20°C). Combined, these cold effects could help promote plaque rupture, but to date no study has been able to demonstrate this.

Risk of cardiac arrhythmias
Arrhythmias are a common cause of sudden cardiac death. Even in healthy volunteers, the simple act of dipping a hand in cold water while holding the breath can cause cardiac arrhythmias (nodal and supraventricular tachycardias). Could cold promote sudden death in people at risk for or with heart disease? Since arrhythmias cannot be detected post-mortem, it is very difficult to prove such a hypothesis. If it turns out that exposure to cold air can promote arrhythmias, people with coronary artery disease may be vulnerable to the cold since the arrhythmia would amplify the oxygenated blood deficit that reaches the heart muscle.

Effects of cold combined with exercise
Both cold and exercise individually increase the heart’s demand for oxygen, and the combination of the two stresses has an additive effect on this demand (see these two review articles, here and here). Exercising in the cold therefore results in an increase in systolic and diastolic blood pressure as well as in the “double product” (heart rate x blood pressure), a marker of cardiac work. The increased demand for oxygen by the heart muscle caused by cold weather and exercise increases blood flow to the coronary arteries that supply the heart. The rate of coronary blood flow increases in response to cold and exercise combined compared to exercise alone, but this increase is mitigated, especially in older people. Therefore, it appears that cold causes a relative lag between the oxygen demand from the myocardium and the oxygenated blood supply during exercise.

In a study carried out by our research team, we exposed 24 coronary patients with stable angina to various experimental conditions in a cold room at – 8°C, specifically a stress test with electrocardiogram (ECG) in cold without antianginal medication and an ECG at + 20°C. We then repeated these two ECGs after taking one drug (propranolol) that slows the heart rate, and then another drug (diltiazem) that causes dilation of the coronary arteries. The results showed that the cold caused mild to moderate ischemia (lack of blood supply) to the myocardium in only 1/3 of the patients. When ECG was done with medication, this effect was completely reversed. The two drugs have been shown to be equally effective in reversing this ischemia. The conclusion: cold had only a modest effect in 1/3 of patients and antianginal drugs are as effective in cold (- 8°C) as at + 20°C.

In another study in the same type of patients, we compared the effects of an ECG at – 20°C with an ECG at + 20°C. The results showed that at this very cold temperature, all patients presented with angina and earlier ischemia.

Hypertension
The prevalence of hypertension is higher in cold regions or during winter. Cold winters increase the severity of hypertension and the risk of cardiovascular events such as myocardial infarction and stroke in people with hypertension.

Heart failure
The heart of patients with heart failure is not able to pump enough blood to maintain the blood flow necessary to meet the body’s needs. Only a few studies have looked at the effects of cold on heart failure. Patients with heart failure do not have much leeway when the heart’s workload increases in cold weather or when they need to exert sustained physical effort. Cold combined with exercise further decreases the performance of people with heart failure. For example, in a study we conducted at the Montreal Heart Institute, cold reduced exercise time by 21% in people with heart failure. In the same study, the use of beta-blocker class antihypertensive drugs (metoprolol or carvedilol) significantly increased exercise time and reduced the impact of cold exposure on the functional capacity of patients. Another of our studies indicates that treatment with an antihypertensive drug from the class of angiotensin converting enzyme inhibitors, lisinopril, also mitigates the impact of cold on the ability to exercise in patients with heart failure.

Cold, exercise and coronary heart disease
It is rather unlikely that the cold alone could cause an increase in the work of the heart muscle large enough to cause a heart attack. Cold stress increases the work of the heart muscle and therefore the blood supply to the heart in healthy people, but in coronary patients there is usually a reduction in blood flow to the coronary arteries. The combination of cold and exercise puts coronary patients at risk of cardiac ischemia (lack of oxygen to the heart) much earlier in their workout than in warm or temperate weather. For this reason, people with coronary artery disease should limit exposure to cold and wear clothes that keep them warm and cover their face (significant heat loss in this part of the body) when working out outdoors in cold weather. In addition, the exercise tolerance of people with coronary heart disease will be reduced in cold weather. It is strongly recommended that coronary heart patients do indoor warm-up exercises before going out to exercise outdoors in cold weather.

Standing up is still doing a little exercise!

Standing up is still doing a little exercise!

OVERVIEW

  • Sedentary lifestyle is associated with a significant increase in the risk of cardiovascular disease, type 2 diabetes, certain types of cancer and an increased risk of dying prematurely.
  • A study of seniors (65 years and older) reported that simply standing for more than an hour a day, without necessarily exercising, is enough to significantly reduce this risk of premature death.

According to recent estimates from the World Health Organization, physical inactivity is directly responsible for around 10% of premature deaths worldwide, an impact similar to those of smoking and obesity. Canada is no exception to this trend, with barely 15% of the population doing the recommended minimum of 150 minutes of physical activity per week and only 5% doing so on a regular basis, i.e. being active for at least 30 minutes a day, five days a week. This sedentary lifestyle is particularly pronounced among older people (60 and over), with barely 10% of this age group being sufficiently active. As a result, it is estimated that the elderly spend on average more than 60% (10 hours and more) of their waking period in sedentary activities, totally devoid of physical activity (Figure 1).

Figure 1. Proportion of waking time spent in sedentary activities by age group. From Matthews et al. (2008).

This is far too much, as numerous studies have clearly shown that high levels of physical inactivity are associated with a significant increase in the risk of cardiovascular disease, type 2 diabetes, certain types of cancer and an increased risk of dying prematurely. There is no doubt that sitting or lying down doing nothing for too long is very bad for health and that itis absolutely necessary to break this bad habit to improve the health of the population.

Standing up is already better
Obviously, the best option to counter the harmful effects of a sedentary lifestyle is to be more physically active. For example, a recent study reports that around 30 minutes of moderate to vigorous physical activity per day (such as brisk walking) seems sufficient to completely cancel out the negative impact of a sedentary lifestyle on the risk of premature mortality.

A study of older people suggests that much lower levels of physical activity may also have positive health effects. In this study, nearly 6,000 American women, ages 63 to 97, wore a research accelerometer for seven days to get accurate measurements of time spent sitting, standing, or moving. During a follow-up period of 5 years on average, the researchers observed that the simple fact of spending more time in a standing position, without doing any other exercise, was enough to significantly decrease the risk of premature death. Compared to the most sedentary women (less than 45 min standing per day), participants who spent the most time standing had a 37% lower risk of death (Figure 2A). These positive effects of standing were even stronger when participants stood and moved at the same time (50% reduction in mortality) (Figure 2B).


Figure 2. Effect of standing (A) or standing with movement (B) on the risk of premature mortality. The values represent the comparison of the mortality rate between the most sedentary people (Q1) and those who are more active (Q4). From Jain et al. (2020).

These results are interesting because many elderly people develop several chronic diseases during aging that weaken them and prevent them from participating in moderate to vigorous physical activities. According to the study, however, these people can improve their health simply by switching from sitting to standing as often as possible.

The transition from sitting to standing requires activating the muscles of the legs and abdominals to lift the body and keep it in balance. These efforts immediately increase blood pressure, heart rate and vascular tone, and the required energy expenditure improves blood vessel function and lipid and carbohydrate metabolism. Although these physiological adaptations are obviously not of the same order as during higher intensity exercise, the results of the study clearly show that they have a positive effect on health and that standing, even without moving, is far better than sitting or lying down for long periods of time.

In short, these results confirm that a sedentary lifestyle is an abnormal behaviour, completely ill adapted to human physiology, and that one should avoid sitting and being inactive for too long as much as possible, regardless of the type of activity performed. And this is true for all ages, young and old alike.