Too Little Sleep May Pose Health Risks, Too Much May Signal Health Problems

As many studies have brought to light in the last couple of decades, sleep isn’t a luxury, but a necessity. The brain is busily working when we’re asleep, mainly to perform critical housekeeping services for itself—but sleep is also crucial for overall health in many ways. A new study in the European Heart Journal finds, as others have, that too little sleep can pose health risks—here, heart and stroke risk. But too much sleep is also not good—but for different reasons. It appears that too much sleep isn’t a risk factor for health issues, but a symptom of already existing ones.



The researchers, from a number of schools around the globe, including Peking Union Medical College and McMaster University, looked at data from over 116,000 adults in 21 countries, who were taking part in the Prospective Urban Rural Epidemiology (PURE). Researchers followed up with the participants for an average of eight years, asking them questions about their lifestyle habits and family histories of health problems. Over this period, about 4,400 people died and about the same number had a cardiovascular event (heart attack or stroke).

Sleep duration was linked to the risk of cardiovascular risk and mortality: People sleeping six to eight hours per night had the lowest risk, while those sleeping eight to nine hours had a slightly elevated (5% greater) risk. People who slept nine to 10 hours had a 17% increased risk, and those sleeping over 10 hours had a 40% greater risk. For people who slept less than six hours, their risk was 5% higher, but this wasn’t statistically significant, meaning it may have been due to chance.

"The general public should ensure that they get about six to eight hours of sleep a day,” said study author Salim Yusuf. “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.”

That’s because while too little sleep may be a cause in itself—stressing the body and leading to inflammation and accompanying health problems—too much sleep is indicative of something else. That is, it’s likely a symptom rather than a cause, a marker of health problems that are already there. Longer sleep duration (over nine hours) has been linked to health problems and mortality risk in previous studies, so it’s not exactly a surprise that this new study found the same thing, albeit in a larger sampling of participants from around the globe.

Interestingly, another study this week finds that getting too little sleep makes people angrier than those who get adequate sleep. This isn’t surprising, since previous studies—and most people's personal experience—tell us that sleep deprivation can seriously affect mood. Rather than accepting bad mood as a necessary sacrifice to maintain our busy lifestyles, maybe we should take it as a symptom itself, of a habit that needs to change for the sake of long-term health.


Naps slightly offset the risk that came from getting less than six hours, which the authors suggest may be a compensatory mechanism.

"Although daytime napping was associated with higher risks of death or cardiovascular problems in those with sufficient or longer sleep at night, this was not the case in people who slept under six hours at night,” said study author study author Chuangshi Wang in a statement. “In these individuals, a daytime nap seemed to compensate for the lack of sleep at night and to mitigate the risks."

The authors call for getting what's generally been recommended, six to eight hours per night. If you routinely get significantly more, you might want to investigate potential underlying causes. And as always, treating sleep as important an activity as eating or staying hydrated is key.

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