No surprises: 6-8 hours is best
Association of estimated sleep duration and naps with mortality and cardiovascular events: a study of 116 632 people from 21 countries. EHJ (2018) 0, 1–10; Wang C, Bangdiwala SI, Rangarajan S, et al.
In our busy workaholic world, we would like a study that shows that sleeping less has no impact on health but in our heart of heart, we know that it probably does.
This analysis looked at data from the international PURE (Prospective Urban Rural Epidemiology) study to examine the association between sleeping patterns and cardiovascular events in more than 110,000 people. Based on analysis of self-reported data over a median follow-up of 7.8 years that was adjusted by age and gender, individuals with relatively long (>8 hours per day) and relatively short (≤6 hours per day) estimated total sleep durations had a higher risk of a composite outcome of major cardiovascular outcomes. However, an additional analysis that was adjusted for lifestyle behaviour, health status, and demographic characteristics found a significant trend for a greater risk of the composite outcome for those with sleep durations of more than 9 hours per day and no significant increase in events in the group with less than 6 hours sleep.
These findings suggest a lower risk of major cardiovascular events and deaths in people with 6 to 8 hours of total daily sleep. Sleeping less is actually better than sleeping too long.
One possible explanation may be that people who have underlying illnesses are more tired, and hence they need to sleep longer. Therefore, longer sleep might not be harmful in itself, but it could be a marker of underlying and perhaps unrecognised disease. The limitation of the study was that it relied on questionnaires, and it is quite possible that the self-reported data are not accurate. We should not conclude that short sleep is fine, but perhaps patients who need to sleep long may have an underlying disease that affects their prognosis.