Study Links Sleeping Too Much With a Higher Risk of Death and Cardiovascular Disease; Experts Question Which Causes Which
Too much sleep may be as a result of lingering health issues.
You know not getting enough sleep brings consequences to your health and wellness. But that doesn’t necessarily mean that extremely long sleepers are the picture of perfect health.
Recent research suggests that sleeping for more than six to eight hours a day (including naps), is connected to a higher risk of death and cardiovascular disease, according to a large study published in the European Heart Journal on December 5, 2018.
The experts note that the findings do not mean that too much sleep necessarily causes worse health. The results of the study, rather, may mean that too much sleep may be a warning sign of another health problem.
“Given that the nature of observational studies is that they present the association rather than proof a causal relationship, we cannot say that too much sleep per se causes poorer health,” says Chuangshi Wang, the lead study author and a PhD student at the Chinese Academy of Medical Sciences Peking Union Medical College in Beijing. “It’s possible that too much sleep is a marker for other causes of cardiovascular diseases and death.”
The research used self-reported survey data from 116,632 adults from 21 countries, all between ages 35 and 70, who were part of the Prospective Urban Rural Epidemiology (PURE) study. The study followed the individuals for a median of 7.8 years, during which 4,381 deaths and 4,365 major cardiovascular events were reported.
The data showed that individuals who reported sleeping six to eight hours per night were least likely to have cardiovascular disease or die during the nearly eight years over which the data were collected.
Those who reported sleeping eight to nine hours had a 5 percent increased risk of developing cardiovascular disease or dying compared with those who slept six to eight hours per night; those who reported sleeping 9 to 10 hours had a 17 percent increased risk of cardiovascular disease or dying compared with those who slept six to eight hours per night; and those who reported sleeping more than 10 hours per night had a 41 percent increased risk of cardiovascular disease or dying compared with those who slept six to eight hours per night.
Individuals who slept six or fewer hours had a 9 percent increased risk of cardiovascular disease or dying compared with those who slept six to eight hours per night, though the researchers determined that finding was not statistically significant because of the data (likely that there were not enough individuals sleeping fewer than six hours per night to make a reliable comparison, as had been done for the other groups).
Sleep Apnea and Other Underlying Problems May Be Behind Long Sleep and Contribute to Poor Health
While the study findings may seem to suggest that too much sleep could hurt your health, experts agree it’s more likely that the study findings are a hint that too much sleep is a sign of other health issues.
“We know that too little sleep is a problem; there’s risk of cardiovascular problems, quality of life,” says Alcibiades Rodriguez, MD, the medical director of New York University Langone Health’s Comprehensive Epilepsy Center and Sleep Center in New York City. Dr. Rodriguez was not involved in the study. “But for sleeping too much, the question is really what is the underlying cause.”
Researchers did not collect information for this study on those potential underlying problems that may be related to a higher risk for death or cardiovascular disease, such as sleep disorders including sleep apnea.
“If sleep apnea is left undiagnosed, it’s associated with heart failure, high blood pressure, arrhythmia,” says Andrew Freeman, MD, a cardiologist at National Jewish Health in Denver. Freeman was not involved with the study. “One thing I hear very commonly from my sickest patients with systemic and severe disease is that they’re sleeping a lot.”
A key take from this new research may be that oversleeping is a warning sign of other health problems, Dr. Freeman says.
According to Wang, the researchers did adjust their analyses for people who showed a high likelihood of sleep apnea and excluded those they suspected of having sleep disorders. Doing so did not change the results, Wang says.
Others say that approach may not have adequately controlled for how much those sleep disorders may have influenced the results.
“They’ve adjusted statistically, but maybe there are confounding factors in the background that are not being taken into consideration, and that’s why we’re seeing the relationships. We still don’t completely understand, from a basic level, why these findings are there,” says Reena Mehra, MD, the director of sleep disorders research in the Sleep Center at Cleveland Clinic’s Neurological Institute.
She says the sleep apnea patients she sees need 9 to 10 hours of sleep nightly, and nap a lot during the day because they don’t get good quality sleep at night.
“That’s a big confounding factor,” she says. “Many studies have shown that, with increasing severity of sleep apnea, there’s an increased risk for mortality over follow-up periods ranging from 5 to 10 years.”
Naps Can Help Compensate for Too Little Sleep, not Sleeping Better Should Be the Goal
Researchers noted that fewer studies have been done on the association between naps and mortality or cardiovascular events (compared with research looking at overall sleep).
The new data showed that napping was associated with higher risks of negative outcomes in people who slept over six hours at night. People who slept less than six hours a night appear to mitigate their risks by taking naps, according to the research.
For adults who work during the day and sleep at night, their circadian rhythms naturally make them most likely to want to nap (if at all) between 2 p.m. and 6 p.m., Rodriguez says.
“The question is how many of the [study participants] didn’t nap, and then started to nap around age 55 to 60. Is it a sign of an underlying [health] issue or that they’re not getting enough sleep at night?” Rodriguez says.
In Dr. Mehra’s clinical practice, she generally discourages patients from napping because it reduces the pressure to sleep at night. But if there’s a sleep disorder, such as untreated sleep apnea, you’re not getting good quality sleep and napping can help compensate for that, she says.
So, What Is the Actual Amount of Sleep I Need?
Another interesting question this study begs is if there is an actual not-too-much, not-too-little quantity of nightly sleep that is a sign of good health, what is it?
The National Sleep Foundation (NSF) recommends adults get seven to nine hours of sleep; no less than six hours or more than 10 hours. The American Academy of Sleep Medicine and the Sleep Research Society recommend adults get seven or more hours of sleep and do not recommend an upper limit. For this data, individuals who slept six to eight hours per night saw the least amount of cardiovascular problems and early mortality.
“There’s never one optimal number for every single person. There’s always going to be a bit of a range. If you sleep five hours and 58 minutes, you’re not in immediate trouble,” Freeman says. “It’s hard to say the exact amount of sleep you need, but [the study found] there’s a ‘Goldilocks’ time right around six or seven hours a night.”
(It’s worth noting that several other studies — upon which the NSF’s most recent guidelines were based — have suggested that seven to nine hours of sleep per night is the ideal range based on the other health outcomes those studies were looking at. Those guidelines and the research supporting them were published in the March 2015 issue of the journal Sleep Health.)
But you don’t necessarily need to panic if your normal sleep patterns fall outside that range. Rodriguez says that you’ll know your ideal amount of sleep when you are in a pattern of getting sleepy at the same time of day, fall asleep, and wake up at a regular hour without an alarm, feeling awake and alert.
“If you function well with six hours of sleep per night, that’s probably normal for you,” he says.
Most important is recognizing what’s normal for you and paying attention to whether your sleep pattern changes, Rodriguez says — which could be a sign there’s an underlying health problem you may need to address.
“It may be a sign of a sleep or medical disorder and you should see a clinician,” he says. “If you’re sleeping nine hours, and all of a sudden it’s not enough, you’re tired in the afternoon, you need to be aware. If you’re sleeping that much and feel healthy, and have no medical problems, you don’t need to feel worried about it.”