Getting eight hours of sleep a night is possibly the most ubiquitous slice of health advice on the planet. From the time you are a child, you’re made aware that you need those eight hours of shut-eye and at the very least you’re told to aim for six. For children, getting less than that can lead to growth and physical health challenges, and for adults, it can contribute to sicknesses and even mental health problems. For the most part, steering clear of insufficient sleep is a greater focus of health research and information. But new research has flipped the tables and instead focused on the dangers of getting too much sleep.
According to a new study published in the European Heart Journal, sleeping more than the recommended eight hours is linked to an increased risk of death and cardiovascular diseases.
Specifically, after observing data from 21 different countries and seven regions, it was found that people sleeping past the upper limits of the eight-hour recommendation increased their risks by as much as 41 percent. This came from a pool of 116,632 adults between the age of 35 and 70, all studied over the course of 7.8 years.
The researchers found that people who slept for longer than the recommended duration of six to eight hours a day had an increased risk of dying or developing diseases of the heart or blood vessels in the brain. Compared to people who slept for the recommended time, those who slept a total of eight to nine hours a day had a 5% increased risk; people sleeping between nine and ten hours a day had an increased risk of 17% and those sleeping more than ten hours a day had a 41% increased risk. They also found a 9% increased risk for people who slept a total of six or fewer hours, but this finding was not statistically significant. Before adjusting for factors that might affect the results, it was found that 7.8 people of every 1,000 people sleeping six to eight hours a night either developed some form of cardiovascular disease or died each year. But on the opposite end of the spectrum, that number rose to 9.4 people for every 1,000 who slept less than six hours, ironically bringing the entire under sleeping versus oversleeping debacle full circle. According to the CDC, in America that is just over 35 percent of the adult population. Of those sleeping eight to nine hours per night, 8.4 of each 1,000 people developed cardiovascular disease or died each year. Amongst people sleeping nine to 10 hours a night, that number jumped up to 10.4, and of the people sleeping more than 10 hours a night, 14.8 of every 1,000 developed cardiovascular diseases or died each year. That means the risk jumps from five percent to 17 percent, and then to a whopping 41 percent higher risk of cardiovascular diseases and death for every extra hour regularly spent in bed. In total, after the almost eight-year study window was completed, researchers observed a grand total of 4,381 deaths and 4,365 “major cardiovascular events.”
But before you rush to set an earlier alarm for tomorrow (or worry about getting an earlier bedtime tonight) take into account a number of factors that painted the picture for this interesting new finding. Further, while much research has been done on all aspects of sleep and its impacts on health, few have been this inclusive of the global community and typically focus on just one country or a specific region of the world.
The team of researchers looked at the results as observational rather than assuming the cause of the association itself was oversleeping, meaning the oversleeping may be a result of other underlying conditions which would also be associated with earlier deaths. Simply put, excess sleep could happen to be a shared symptom of many others associated with the raised risk of cardiovascular disease or mortality. They also found that daytime napping holds a link to rising risks, which was most common in the Middle East, China, Southeast Asia, and South America.
"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,”says Chuangshi Wang, leader of the study and a Ph.D. student at McMaster and Peking Union Medical College in China.
Ironically (and logically) enough, the study found that daytime napping was most often a direct result of under sleeping.
"If you sleep less for a long time you are more prone to develop chronic disease," says Francesco Cappuccio, professor of cardiovascular medicine and epidemiology at Warwick University, who points out that short sleep duration has been shown to increase high blood pressure, obesity, and diabetes.
The assumed conclusion from these results isn’t that sleeping more than eight hours is in itself a problem, rather underlying health results lead to more sleep and can be an indicator of earlier deaths. More importantly, staying within that optimal six to eight-hour range each night can be a sign of fair health, which is why researchers hoped their findings would encourage doctors to ask their patients more specific questions about their sleep health as a window into their overall health.
Co-author Professor Salim Yusuf, from McMaster University, Ontario, Canada, said, “The general public should ensure that they get about six to eight hours of sleep a day. On the other hand, if you sleep too much regularly, say more than nine hours a day, then you may want to visit a doctor to check your overall health. 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.”
So which is it? Too little sleep or too much sleep that’s going to put your health at the greatest risk? Turns out that six to eight-hour window has been recommended to us since childhood for good reason.