The recommended amount of sleep for adults is six to eight hours a night. Sleeping more than those hours is associated with an increased risk of death and cardiovascular diseases, says a global study published Wednesday in the European Heart Journal, CNN reported.
Looking at data from 21 countries, across seven regions, the research team found that people sleeping more than the recommended upper limit of eight hours increased their risk of major cardiovascular events, like stroke or heart failure, as well as death by up to 41%.
But a possible reason for this could be that people have underlying conditions causing them to sleep longer, which in turn could raise the risk of cardiovascular disease or mortality, explain the authors of the study.
The team, led by Chuangshi Wang, a Ph.D. student at McMaster and Peking Union Medical College in China, also identified a rising risk among daytime nappers.
“Daytime napping was associated with increased risks of major cardiovascular events and deaths in those with [more than] six hours of nighttime sleep but not in those sleeping [less than] 6 hours a night,” Wang said.
But, this was not the case for people who slept under six hours per night.
“In these individuals, a daytime nap seemed to compensate for the lack of sleep at night and to mitigate the risks,” Wang said.
But for those who slept enough at night, “daytime napping was associated with increased risks of major cardiovascular events and deaths,” she said.
Cappuccio has previously conducted research into daily napping among British adults.
“Napping could reflect underlying ill-health (fatigue, tiredness) eventually leading to morbidity and mortality, could be a proxy for sleep deprivation, as a compensatory catch-up mechanism, or could also be a symptom of circadian misalignment,” he said.
Monitoring sleeping patterns
The study had several limitations, Wang pointed out, as participants were asked to self-report their sleeping patterns and the sleep duration was based on the space between going to bed and waking up.
The team also did not collect data on sleep disorders, such as insomnia, which could have an impact on sleep and also affect health, the paper states.
Wang explained that it is usually not feasible to accurately measure sleep time in large population studies.
The researchers hope that their results will encourage doctors to ask their patients about sleeping patterns when discussing general lifestyle factors, to identify any potential underlying health problems.
Salim Yusuf, professor of medicine at McMaster University and the principal investigator of the PURE study, from which the participants were chosen, said, “For doctors, including questions about the duration of sleep and daytime naps in the clinical histories of your patients may be helpful in identifying people at high risk of heart and blood vessel problems or death.”
