Sleeping is a true pleasure. But also, sleeping — sleeping well — is essential to survive and to live longer. However, it would seem that people sleep increasingly less. In fact, one in four adults believes that they do not rest well. That is why it is important to take the time to reflect on our sleep habits, in terms of quantity and quality. The optimal duration of sleep for adults and the elderly is seven to nine hours; for children, it is longer. The current evidence suggests that too little or too much sleep can increase the risk of all-cause mortality; in addition, women are more susceptible to shorter sleep durations.
If you are wondering what exercise has to do with sleep, the answer is: a lot. We know that sleep and exercise influence each other through a complex, reciprocal interaction that includes multiple physiological and psychological pathways. Committing to doing enough physical activity and keeping healthy sleep habits is key to extend life expectancy. Despite the fact that so far the scientific results have not been very conclusive due to some limitations of the studies, we believe that sufficient physical activity can reduce the risk of mortality related to unhealthy sleep. The main limitation of this research, the subjective measurement of physical activity, was overcome in a study about the association of physical activity and sleep duration with risk of mortality that was recently published in the European Journal of Preventive Cardiology.
In it, nearly 100,000 participants of both sexes with a mean age of 62 years had their physical activity objectively measured for an entire week, and mortality outcomes were followed-up for seven years. During that period, just over 1,000 people died from cardiovascular diseases and 1,800 from cancer. Sleep duration was divided into three groups: short (less than six hours a day), normal (six to eight) and long (more than eight). Moderate to vigorous physical activity was divided according to whether or not it met the guidelines of the World Health Organization (WHO): approximately 150 minutes of moderate physical activity or 75 minutes of vigorous physical activity throughout the week, or equivalent combinations.
With these results, an independent association of sleep duration and risk of mortality was observed in a U-shaped pattern, meaning that those who sleep little (less than six hours) or a lot (more than eight) had a higher risk of death than those with a normal sleep duration (six to eight hours). This occurred both with the risk of all-cause mortality and the risk of mortality from cardiovascular causes. However, sleep duration was not associated with risk of cancer mortality.
If we stratify the above association by categories of physical activity, the results are encouraging and favorable for the people who do meet the recommendations of the WHO. Complying with these guidelines decreases the excess risk of mortality (all-cause, cardiovascular and cancer-related) associated with too little or too much sleep. Thus, physical activity may mitigate the harmful association of inadequate sleep durations with mortality. The data also yielded the conclusion that the people with the lowest risk of death were those who had a normal sleep duration (six to eight hours) and who performed large amounts of physical activity.
The most interesting lesson that we can take from this study is that people who sleep for too many or too few hours can reduce their high risk of death, compared to those who sleep the ideal time, if they meet the physical activity recommendations of the WHO. The authors speculate on the mechanisms by which this phenomenon of reducing the risk of mortality occurs in those who sleep many or few hours. Poor sleep is associated with a number of conditions, including hyperarousal of the sympathetic nervous system, insulin resistance, endothelial dysfunction and inflammation. Meanwhile, physical activity strengthens cardiorespiratory fitness, inhibits the inflammatory response and improves glucose metabolism.
This study conclusively confirms that the increased mortality risk due to inadequate sleep duration, whether too long or too short, is exacerbated and aggravated by physical inactivity. Thus, these findings support the integration of physical activity into clinical sleep interventions and public health guidelines.
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