The American Academy of Sleep Medicine, the largest physician-based organization for sleep medicine, recently put out their first recommendations for what is the right amount of sleep
. It advises that adults get at least seven hours every night based on research on the link between inadequate sleep and a number of poor health outcomes.
Although most of us already know that we should get at least seven hours of sleep, a study last month suggested that Americans are creeping down to that cutoff
. The average amount of sleep that they reported getting a night has dropped from 7.4 hours in 1985 to 7.29 hours in 1990 to 7.18 in 2004 and 2012.
For many aspects of health, "it was quite clear that seven to nine hours was good," said Dr. Nathaniel F. Watson, president of the American Academy of Sleep Medicine and a professor of neurology at University of Washington. Watson led the panel of experts that wrote the recommendations. The group looked at more than 300 studies.
Getting only six hours of sleep a night or less was associated with setbacks in performance, including mental alertness and driving ability, and increased risk of heart attack, stroke, diabetes and obesity, Watson said.
There were not enough studies looking at the health of people who got between six and seven hours of sleep or more than nine hours to know how their health fared.
The panel did not put an upper cutoff on the amount of sleep a person should get because, in addition to the lack of evidence, "there are instances where a person might sleep longer if they are recovering from a sleep debt or illness, and we had trouble coming up with a biological way that sleep would be bad for you," Watson said.
Although there have been reports that sleeping nine hours or more
a night is associated with increased risk of death, that link probably has more to do with the fact that the people who slept a lot had underlying illnesses that ultimately did them in, said James Gangwisch, a sleep researcher at Columbia University who helped develop the current recommendations.
In addition, reports of sleeping a lot may actually be an indicator that a person is not exercising or socializing, which can carry health risks.
Sleep and how it relates to body mass and more
The panel looked at studies that reported connections between the amount of sleep that people said they got and their health over long periods. The panel also took into consideration studies that monitored people in sleep labs that controlled how much sleep they got.
For example, Gangwisch and his colleagues have reported a connection between getting less than seven hours of sleep
a night and high body mass index. Separate studies in sleep labs suggest how inadequate sleep could lead to obesity
: it drives up the levels of appetite-inducing hormones.
The weight gain that might be caused by inadequate shut-eye could, in turn, increase the risk of heart attack and stroke, Gangwisch said. In addition, sleep deficits seem to increase blood pressure as several studies have found, which could be bad for heart health.
One small study found that healthy adults had higher blood pressure
after a night when they were only allowed to sleep four hours compared with a night when they were allowed to sleep for eight hours.
It is hard to say, however, if depriving people of sleep for an extended period would have lasting effects on blood pressure and appetite, even though studies linking sleep deprivation with heart disease and weight gain suggest so.
Sleep lab studies usually only investigate the effect of abridged snoozing for several nights, but people might adjust somewhat to sleep deprivation if it became the norm for them, Gangwisch said.
Although the recent recommendations are for the appropriate amount of shut-eye, getting bad sleep could be just as harmful as not getting enough sleep. Among the most common sleep disorders are insomnia and obstructive sleep apnea, which causes people to stop breathing intermittently throughout the night. About 10% of adults have chronic insomnia; obstructive sleep apnea affects an estimated 24% of men and 9% of women.
Obstructive sleep apnea in particular can take a toll in many ways beyond just shortening the amount of sleep you get, Watson said. The condition can increase blood pressure (separately from the effect of not getting enough sleep), deprive the body of oxygen, cause irregular heartbeat and make the blood more sticky, all of which can increase the risk of heart disease and stroke, he said.
A study that was presented this week at the European Society of Cardiology meeting found that men who had a sleep disorder were between 2 and 2.6 times more likely to have a heart attack
and 1.5 to 4 times more likely to have a stroke over the 14-year period of the study.
Not sleeping well? Talk to the doc
"This study underscores to me the importance that if a person doesn't think they are sleeping well, they should talk to their doctor," said Kristen Knutson, an assistant professor of medicine at the University of Chicago who was not involved in the study.
Signs that you are not sleeping well or enough include needing a lot of caffeine to get through the day and falling asleep during a meeting or movie, which Knutson said does not usually happen in well-rested people no matter how bored they are.
Some people might need more or less than seven hours of shut-eye. To know what is right for you, see how long you sleep when you are a couple of days into a vacation and the alarm does not go off, Knutson suggested. (The first couple of days you might sleep longer because you are catching up.)
Knutson agrees with the advice that there does not seem to be a danger in sleeping too much. "People generally don't sleep more than they should, and if you are laying in bed and can't sleep, the general recommendation is to get up," she said.
There are a number of strategies for making the most of your slumber
. These include going to sleep and waking up about the same time every day, making your bedroom dark and cool and avoiding caffeine too close to bedtime.
"Some people view sleep as an obstruction to success, and we would rather have people view it as a tool for success," Watson said. "We really want people to prioritize their sleep and understand that it is as important to their overall well being as diet and exercise," he added.