New research finds that both insufficient and excessive sleep may raise the risk of cardiovascular problems and premature death.

The Centers for Disease Control and Prevention (CDC) report that one-third of the United States population does not get enough sleep.

The CDC also warn that sleep deprivation raises the risk of various chronic conditions such as diabetes, cardiovascular disease, obesity, and depression.

But, according to new research appearing in the European Heart Journal, sleeping too much may affect health just as negatively as sleeping too little.

Chuangshi Wang, a doctoral candidate at McMaster University in Ontario in Canada, and Peking Union Medical College at the Chinese Academy of Medical Sciences in China, is the lead author of the new paper.

The health consequences of too much sleep

Wang and colleagues examined the sleeping habits of more than 116,000 people aged between 35 and 70 years who had enrolled in the Prospective Urban Rural Epidemiology (PURE) study.

In their analysis, the researchers also included information about the participants' socioeconomic status, lifestyle habits, physical activity, diet, use of various medications, and family history of chronic conditions.

Overall, 4,381 people died and 4,365 people had a heart attack or stroke during the 8-year follow-up period of the PURE study.

The analysis by Wang and her team revealed that people who regularly slept more than the recommended 6–8 hours a night were more likely to die prematurely or develop cardiovascular disease.

More specifically, the risk of premature death or cardiovascular conditions was 5 percent higher for people who slept 8–9 hours than for people who slept the recommended amount.

Those who slept 9–10 hours were 17% more likely to die or develop heart and blood vessel conditions. Similarly, people who regularly slept more than 10 hours were 41% more likely to die prematurely or develop cardiovascular problems.

Also, the study found a 9% higher risk of the outcomes mentioned above among those who slept 6 hours or less. However, the authors caution that this increase was not statistically significant.

Wang comments on the findings, saying, "Our study shows that the optimal duration of estimated sleep is 6 to 8 hours per day for adults."

"Given that this is an observational study that can only show an association rather than proving a causal relationship, we cannot say that too much sleep per se causes cardiovascular diseases," she cautions.

"However, too little sleep could be an underlying contributor to death and cases of cardiovascular disease, and too much sleep may indicate underlying conditions that increase risk."

Corresponding author Dr. Salim Yusuf, who is the principal investigator of the PURE study, and a professor of medicine at McMaster, also comments on the findings.

"The general public should ensure that they get about 6 to 8 hours of sleep a day. On the other hand, if you sleep too much regularly, say more than 9 hours a day, then you may want to visit a doctor to check your overall health."

Dr. Salim Yusuf

"For doctors," continues Dr. Yusuf, "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."