With almost 18 million deaths each year, or 31% of total global mortality, cardiovascular disease is the leading cause of death worldwide. It is a general term for a group of conditions that affect the heart and the vascular system and include coronary heart disease (affecting the vessels that supply the cardiac muscle), cerebrovascular disease (affecting the vessels that supply the brain), rheumatic diseases, thrombosis, and many more. Of these deaths, an estimated 7.4 million are due to coronary heart disease and 6.7 million to stroke. A third of these deaths occur prematurely in people under the age of 70.
Of course, cardiovascular disease is also strongly associated with aging. And the increase in the incidence of these diseases is partly due to the aging of the population. Cardiovascular diseases are classified as non-communicable diseases. And it is possible to prevent most of these diseases by reducing behavioral risk factors like smoking, alcohol consumption, unhealthy diet, sedentary lifestyle and physical inactivity.
The health benefits, particularly for cardiovascular diseases, of reducing sedentary lifestyle and increasing physical activity are now well known. Do not hesitate to consult our articles on the subject. However, many of these studies are based on self-reported physical activity methods, which are often very imprecise. Most people tend to overestimate their physical activity and fitness level. In addition to this, these methods have a very limited ability to assess the duration of sedentary behaviors (sitting, lying down, doing nothing, reading a book or watching TV) and low-intensity activities (walking in the house, for example). This is particularly limiting for the study of physical activity in older people who spend at least 60-75% of their time in a sedentary state. Since adherence to official recommendations for physical activity is generally very low, it would be interesting to know what minimal dose of physical activity could benefit this population.
In an attempt to fill this information gap, Swedish and Norwegian researchers analyzed data from 3,343 people, aged 70 or more, who participated in a prospective study between 2012 and 2017. During this period, all these people wore an accelerometer for a week to record the actual level of activity in their daily life. Of these people, 1,604 (48%) adhered to public health recommendations by engaging in at least 30 minutes per day of moderate to vigorous physical activity during that week of observation. Finally, between 2012 and 2017, the researchers carried out a complete health follow-up and recorded the number of incidents and deaths due to a stroke or a myocardial infarction.
Of the participants, 3% had a previous stroke and 4% had a myocardial infarction, 20% were diagnosed with depression, 18% had cancer and 57% were taking medication for high blood pressure. And during the follow-up period, 124 events occurred: 39 strokes, 35 myocardial infarctions and 50 deaths, i.e., an incidence of 14.2 per 1000 people.
The main results show that every additional 30 minutes of low-intensity physical activity was associated with 11% lower risk of stroke, heart attack or death. This risk decreased to 36% for each additional 30 minutes of moderate-intensity physical activity.
When it comes to sedentary time (that is, sitting, lying down), each hour spent increased the risk of stroke, heart attack or death by 33%. But this risk was modified by the level of physical activity. In fact, each hour of sedentary behavior was associated with a risk of stroke, heart attack or death of 29% for people who practiced 15 minutes or less of physical activity at moderate intensity. This risk decreased to 20% for people practicing between 16 and 29 minutes per day of physical activity at moderate intensity, and to 11% for people practicing more than 30 minutes per day.
These findings were independent of sex, social status, health status, smoking, medication use, and cardiometabolic risk factors.
With the increase in sedentary lifestyle (overall, more time spent sitting) and physical inactivity (not following public recommendations on physical activity), studies on the benefits of physical activity in reducing risks of health problems have increased significantly in recent years. Part of the literature is now turning to the benefits of increasing low-intensity physical activity, and thus, in reducing sedentary time. This is even more relevant given that seniors tend to spend a large majority of their waking time being sedentary and performing low-intensity activities. However, as the results of this observational study show, moderate-intensity activities have the greatest impact on reducing the risk of cardiac events or overall mortality. And it is the more sedentary seniors who benefit the most from increased physical activity, whether light or moderate.
Of course, given its nature, this study cannot establish any causal link. In addition, it is also not possible to exclude reverse causation. That is, it is not possible to know whether it is the physical activity which really decreases the risk of cardiac events or if it is the initial health condition which limits or not the physical activity of the elderly participating in this study. However, the scientific evidence for the benefits of regular physical activity on the human body is such that there is no reason to believe that physical activity would not be beneficial, regardless of age. It simply seems necessary to us to implement good hygiene as early as possible in one's life. As the authors very well conclude: "Regardless of intensity, the more you move and the less you sit, the better." And if the intensity can be moderate to intense, and the duration of practice can be increased, the health benefits will be even stronger, and could even reduce the harmful effects of a sedentary lifestyle.
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