Smoking continues to decline among young people

Smoking continues to decline among young people


  • The percentage of young Canadians aged 16–19 who smoke cigarettes on a regular basis continued to decline between 2017 and 2019, from 3.8% to 2.3%.
  • This decrease in youth smoking is correlated with an increased use of electronic cigarettes, with the proportion of young people having vaped at least once in their lives increasing from 29 to 41% during this period.
  • These vapers are, however, mostly occasional or regular smokers, which suggests that the electronic cigarette represents an alternative to traditional cigarettes and contributes to the decline in smoking observed among young people.

One of the greatest successes of tobacco control in the last 20 years has been the dramatic decline in smoking among young adolescents. As we mentioned in another article, while nearly 25% of teens in grade 12 smoked cigarettes daily in the early 2000s, this proportion is now around 2%. This drastic drop in youth smoking is of paramount importance, as more than 90% of regular adult smokers started smoking before the age of 18, during the experimentation period of adolescence. Such a low rate of smoking among young people will therefore necessarily translate into a significant reduction in the number of adult smokers over the next few years and a decrease in the incidence of the many diseases caused by tobacco, which is the ultimate goal of tobacco control.

However, this good news is rarely mentioned: instead of celebrating this decline in youth smoking, much more attention has been paid to the recent emergence of a new trend, namely the increase in the number of young people who have experimented with electronic cigarettes in recent years. According to a recent study by Dr. David Hammond’s group, e-cigarette use is indeed on the rise among young Canadians, with about 41% of 16-19-year-olds having tried these products at least once, compared to 29% in 2017 (Figure 1). This increase is correlated with the appearance on the market of e-cigarettes of the Juul type, extremely attractive and easy-to-use devices, which allow the absorption of a significant amount of nicotine (see our article on the subject).

Figure 1. Frequency of use of electronic cigarettes by 16-19-year-olds. Adapted from Hammond et al. (2020). Note that non-smokers represent less than 1% of total vapers.

However, it is important to note that the vast majority of this vaping is experimental in nature. While almost half of young people have used these products at least once in their life, this proportion decreases to 18% in the last month, 12% in the last week, eventually reaching just over 5% of regular vapers (20 or more times in the last month). Daily use of electronic cigarettes is therefore still a relatively uncommon phenomenon among young people and certainly does not reach “epidemic” proportions, as is often said. Not only do regular vapers remain a very small minority, but most (over 85%) of these young people already smoke cigarettes occasionally or regularly. Young people who have never smoked cigarettes represent less than 15% of regular vapers, which corresponds to less than 1% of all vapers (Figure 1, red rectangle).

Overall, these results paint a much more nuanced picture of the phenomenon of vaping among young people than what we regularly hear in the media: the vast majority of those who want to experience the effect of tobacco are now turning to new forms of nicotine such as electronic cigarettes, but even then the regular users of these products remain relatively few, and are mostly young people who are primarily attracted to tobacco.

Initially, the main concern raised by the increased use of electronic cigarettes by young people is that it could lead to an increase in smoking in this population. This is clearly not the case as the number of young smokers continues to decline each year, even since the introduction of the electronic cigarette, and studies even indicate that these products have led to an acceleration of this decline in the smoking rate. The study mentioned earlier observes the same phenomenon, i.e. that the increase in vaping observed over the past two years in Canada is directly correlated with a significant decrease (40%) in smoking among young people (Figure 2).

Figure 2. The increase in the percentage of young vapers is correlated with a decrease in the percentage of young smokers. From Hammond et al. (2020).

Instead of being a gateway to tobacco as was initially feared, the electronic cigarette therefore seems to represent more of an alternative to traditional cigarettes. The abandonment of cigarettes by young people in favour of this new technology is not so surprising when you consider the unpleasant smell of cigarettes, the exorbitant prices of tobacco, and the ban on smoking in almost all public places. In such a context, it is difficult to conceive why a user of electronic cigarettes might be tempted to turn to conventional tobacco products.

Obviously, everyone agrees that it would be better if young people did not use either electronic cigarettes or tobacco. But if we assume that adolescence is an intense period of experimentation, it is vastly preferable that this experimentation with the effects of nicotine be done in the form of vaping rather than of tobacco cigarettes.

It should be noted that with an electronic cigarette, the vaper inhales an aerosol containing nicotine, but without the multiple carcinogenic molecules, carbon monoxide and fine particles that are generated during the combustion of tobacco (at around 900 °C). This last point is the most important: it is the combustion products of tobacco cigarettes that cause health problems, not the nicotine. The latter is a drug that creates addiction to tobacco and pushes people to smoke, but it has no major effects on health and is especially not responsible for cardiovascular diseases or lung cancer that result from smoking. According to the British public health agency, Public Health England, the vapour generated by electronic cigarettes is much less toxic than the smoke produced by the combustion of tobacco, and therefore vaping presents considerably less risk to health than smoking.

It is also important to remember that while there is great concern about the increase in vaping among young people, electronic cigarettes are certainly not the main threat to their health. For example, surveys in the United States indicate that more than 15% of high school youth regularly drink large amounts of alcohol (binge drinking), an extremely harmful behaviour that is associated with an increased risk of accidents, violence and several serious diseases (stroke, cirrhosis, cancer). Although the consumption of alcohol is more socially acceptable than that of electronic cigarettes, it should be kept in mind that excessive alcohol consumption represents one of the main causes of death on a global scale and is therefore much more harmful to the health of youth than electronic cigarettes. Before considering banning vaping products under the pretext of “protecting our young people”, as is sometimes argued, we must take into account these relative risks and avoid any form of prohibition that could have the effect of leading them towards combustible tobacco products, which are much more harmful to health. Despite the often very alarmist reports, the transition from tobacco to e-cigarettes is a less worrying trend than it might appear at first glance and represents a typical example of harm reduction in public health.

Can exercise protect against respiratory infections?

Can exercise protect against respiratory infections?


  • Participants in more than 14 studies were randomly separated into two groups: one group who did not exercise and one who exercised regularly and under supervision.
  • Exercise did not reduce the incidence of acute respiratory infections.
  • Exercise appears to reduce the severity of symptoms associated with episodes of acute respiratory infections.
  • According to several other studies, exercise can improve the immune response to viruses, bacteria and other antigens. Regular physical activity and frequent exercise may reduce or delay the aging of the immune system.

COVID-19 caused by infection with the SARS-CoV-2 virus particularly affects people who have certain risk factors (advanced age, male) or a comorbidity such as chronic respiratory disease, obesity, cardiovascular disease, diabetes, hypertension and cancer (see this article). A healthy lifestyle, including eating well, not smoking, consuming alcohol in moderation, and exercising regularly, is the best way to prevent many diseases such as diabetes, cancer and cardiovascular disease. Also, certain conditions are associated with a decrease in immune activity, for example, stress, diabetes and the deficiency of certain dietary compounds like vitamin D and zinc. By its action on these conditions, exercise is likely to influence our resistance to infections.

Can exercise prevent acute respiratory infections, including COVID-19? Researchers at the Cochrane Library recently updated a systematic review of the effect of exercise on the occurrence, severity and duration of acute respiratory infections.  The systematic review included 14 studies of 1377 healthy individuals aged 18 to 85 who were followed for a median period of 12 weeks. The participants were randomly separated into two groups: one who did not exercise and one who exercised regularly. In most cases, the exercise was supervised and was performed at least three times per week. The exercise sessions lasted 30 to 45 minutes and consisted of moderate intensity exercise such as walking, cycling, treadmill or a combination of these exercises. Exercise did not have a significant effect on biochemical parameters, quality of life or number of injuries.

Exercise did not decrease the number of acute respiratory infections (ARI) episodes, nor the proportion of participants who had at least one episode of ARI during the study, or the number of days with symptoms during each of these episodes. On the other hand, exercise was associated with a decrease in symptom severity in two studies and in the number of days with symptoms during the total study duration (4 studies). The study authors indicate that certainty about the data is low and that data from ongoing or future studies may impact their conclusions.

Exercise and the immune system
The immune system is very responsive to exercise, depending on both the duration and the intensity of effort (see this review article). Exercise causes multiple micro-injuries to the muscles, triggering a local and systemic inflammation reaction. During a moderate to high intensity exercise session lasting less than 60 minutes, the number of leukocytes (white blood cells) and several cytokines (proteins produced by the immune system to stimulate the proliferation of defence cells) increases rapidly in the bloodstream. The increase in the number of neutrophils (a type of white blood cell) often lasts for up to 6 hours after the end of the exercise session. This physiological response to stress caused by exercise is followed, during the recovery period, by a drop in the number of leukocytes in the bloodstream to a level below that measured at the start of the exercise session.

Although exercise transiently increases markers of inflammation, including several cytokines (interleukins, chemokines, interferons, and others), at rest, people who exercise regularly have lower blood levels of these pro-inflammatory proteins than people who exercise little or not at all or who are obese. Regular exercise therefore appears to moderate the inflammatory response and promote an anti-inflammatory environment in the body. The persistent increase in markers of inflammation (chronic inflammation) is linked to several conditions and diseases, including obesity, osteoarthritis, atherosclerosis and cardiovascular disease, chronic kidney disease, liver disease, metabolic syndrome, insulin resistance, type 2 diabetes, chronic obstructive pulmonary disease, dementia, depression, and various types of cancers. In short, exercise reduces the negative effects on the immune system of a recognized factor that is diabetes and the associated insulin resistance.

It is known that in severe forms of COVID-19 an exaggerated inflammatory reaction called “cytokine storm” destroys the cells of the pulmonary endothelium that allow oxygenation of the blood and body. Could regular exercise that provides a less inflammatory environment protect us in the event of a SARS-CoV-2 virus infection? This has not been demonstrated, but it is certainly a hypothesis that will need to be examined. Moreover, it seems that in the elderly, immune aging (also called “immunosenescence”) is associated with a decline in the cells that regulate the immune response. It is because of this decline that we observe an increase in immune disorders such as autoimmune diseases and an increase in cancers. However, the cytokine storm would be secondary to the lack of control by these cells. A healthy immune system would be less likely to lack these “regulatory” cells.

Suppression of immunity in athletes: Myth or reality?
In recent decades, an idea has taken root in the scientific literature according to which aerobic exercise, particularly if it is vigorous and of long duration, can interfere with immunocompetence, i.e. the body’s ability to produce a normal immune response in response to exposure to an antigen. This idea is now increasingly questioned and has even been called a myth by some researchers. This hypothesis dates from the early 20th century, when fatigue was believed to contribute to infections that caused pneumonia, but it was not until the 1980s–1990s that studies verified this assertion with professional and amateur athletes. In general, it is increasingly certain that it is “psychological” stress rather than physical stress that is immunosuppressive. For example, a study in the 1980s among medical students showed that immune capacity collapsed within 24 to 48 hours of exams. The “mental” stress on the eve of competitions could be the comparison. Exercise is a great stress reliever for most people.

One of the studies indicated that one third of the 150 runners participating in the 1982 Two Oceans ultramarathon (56 km) in South Africa reported symptoms of upper respiratory tract infection (runny nose, sore throat, sneezing) within two weeks of the race. The control group reported half as many symptoms of upper respiratory tract infection than runners. Similar results were obtained from athletes who participated in the Los Angeles Marathon (42 km) in 1987. Among the 2311 participants who completed the race and who had not reported symptoms of infection in the week before the race, 12.9% reported symptoms of infection in the week following the race. Only 2.2% of participants who dropped out of the race (for reasons other than health reasons) reported symptoms of infection in the week after the race. Another study conducted at the same time did not find an association between aerobic exercise and the risk of upper respiratory tract infection for runs over shorter distances, namely 5 km, 10 km, and 21 km (half marathon). This suggested that the risk of infections increases only after exercising for a very long period of time.

The major problem with these studies is that they are questionnaire-based and none of the infections reported by athletes were confirmed in the laboratory. In a 2007 study, researchers took swabs and tested athletes who reported symptoms of upper respiratory tract infection over a period of 5 months. Only 30% of the cases reported by the participants were associated with the presence of viruses, bacteria, or mycoplasmas. These results suggest that the symptoms experienced by athletes in previous studies may not have been caused by infection, but rather by other causes, including allergies, asthma, inflammation of the mucous membranes, or trauma to the epithelial cells of the airways caused by increased breathing or exposure to cold air.

The decrease in leukocytes in the bloodstream that is observed after exercise has led to the so-called “open window” hypothesis that intense exercise causes transient immunosuppression during the recovery period. During this “open window”, athletes would be more susceptible to viral and bacterial infections. Another hypothesis would be that of the recruitment of white blood cells to repair small damage to the muscles. Indeed, tissue damage, whether mechanical or infectious, causes the release of cytokines, which “call” the defences to “see what happens.” Yet, contrary to the studies cited above, recent studies indicate that exercise is rather associated with a reduction in the incidence of infections. There are as many epidemiological studies that show that regular exercise is associated with a reduction in infections as there are that show that regular exercise is associated with an increase in infections, but the former are less taken into account than the latter in the literature on exercise immunology.

For example, a Swedish study of 1509 men and women aged 20 to 60 found that high levels of physical activity are associated with a reduced incidence of upper respiratory tract infections. Studies of ultramarathon runners, one of the most taxing sports, have shown that these people report fewer days of absence from school or work due to illness compared to the general population. For example, the average number of sick days reported annually was 1.5 days in a study of 1212 ultramarathon runners and 2.8 days in another study of 489 161-km ultramarathon runners, while that year the number of sick days reported in the American population was 4.4 days. An often overlooked aspect of outdoor exercise is its vitamin D intake with exposure to the sun. The longer the routes, the greater the exposure and endogenous skin production of vitamin D. Vitamin D intake would be beneficial for the regulatory cells of the immune system.

In summary, contrary to the immunosuppression (“open window”) hypothesis, regular exercise can be beneficial for the immune system, or at least not harmful. Exercise does not increase the risk of diagnosed opportunistic infections. Exercise can improve the immune response to viruses, bacteria, and other antigens. Regular physical activity and frequent exercise may reduce or delay the aging of the immune system.

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.