Getting too little or too much sleep is associated with a shorter lifespan, but research involving over 90,000 adults has revealed that some of the negative effects can be counteracted with physical activity. The study showed that increased levels of physical activity diluted the mortality risks related to too little or too much sleep.
Adequate exercise and sound sleep help extend life expectancy. However, the interaction of physical activity with sleep duration to promote health has not been clear.
The primary limitation of previous research was the use of subjective sleep and physical activity which may not be accurate. By comparison, an accelerometer device measures movement and thus provides more reliable, objective estimates of sleep duration and activity.
This study examined the combined effects of sleep duration and physical activity on the risk of death using accelerometry. The study involved 92,221 individuals aged 40 to 73 who wore an accelerometer bracelet for 1 week.
Nighttime sleep duration of less than 6 hours was classified as short, 6 to 8 hours as normal, or longer than 8 hours. Total volume of physical activity was divided into low, intermediate, and high tertiles. Moderate to vigorous intensity physical activity was classified according to WHO guidelines.
Death registries provided mortality data. The primary outcome was death from all causes. Secondary outcomes were death due to cancer or cardiovascular disease.
The mean age of the participants was 62, and just over half were women. During an average 7-year follow-up, 3,080 people died, 1,871 died of cancer, and 1,074 died of cardiovascular disease.
The influence physical activity had on the impact of sleep on mortality was examined. Activity volume was first considered the intensity of physical activity.
Factors such as gender, age, ethnicity, education level, deprivation, sleep measurement season, shift work, diet, body mass index, alcohol consumption, and smoking were adjusted for influencing the association.
In participants with low activity levels, short and long sleep were linked to 16% and 37% increased risk of death from all causes, respectively.
Only short sleep was harmful in individuals with intermediate levels of exercise, resulting in a 41 percent increased chance of death from all causes. Sleep duration was not associated with risk of death in individuals with high levels of exercise.
Backsleepers with low levels of exercise had a 69 percent increased risk of cardiovascular death, which was negated when exercise was increased to moderate or high levels. Long sleepers with low levels of exercise had a 21 percent increased risk of dying from cancer that was canceled out with moderate or high levels of exercise.
Similar results were observed for moderate to vigorous intensity physical activity. Short and long sleep were linked to 31% and 20% increased risk of death from all causes in individuals who did not meet WHO recommendations.
These risks have been nullified in people by following WHO guidelines. Back sleepers who did not meet the intensity of exercise recommendations had a 52% increased risk of cardiovascular death, which was negated in individuals who met the recommendations.
Backsleepers who didn’t meet the recommendations had a 21 percent increased risk of dying from cancer that was negated in people who followed the WHO recommendations.
The findings indicate that health-promoting efforts that target both sleep duration and physical activity might be more effective at preventing or delaying premature death of middle-aged and older individuals than focusing on just one behavior.
Individuals who consistently get healthy amounts of physical activity and sleep would be an ideal scenario. This study, however, indicates that getting enough exercise could partially offset the detrimental impact of too little or too much sleep.
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