How Much Sleep Do You Really Need?

Sleep is one of the richest topics in science today: why we need it, why it can be hard to get, and how that affects everything from our athletic performance to our income. Daniel Kripke, co-director of research at the Scripps Clinic Sleep Center in La Jolla, Calif., has looked at the most important question of all. In 2002, he compared death rates among more than 1 million American adults who, as part of a study on cancer prevention, reported their average nightly amount of sleep. To many, his results were surprising, but they've since been corroborated by similar studies in Europe and East Asia. Kripke explains.

Q: How much sleep is ideal?

A: Studies show that people who sleep between 6.5 hr. and 7.5 hr. a night, as they report, live the longest. And people who sleep 8 hr. or more, or less than 6.5 hr., they don't live quite as long. There is just as much risk associated with sleeping too long as with sleeping too short. The big surprise is that long sleep seems to start at 8 hr. Sleeping 8.5 hr. might really be a little worse than sleeping 5 hr.

Morbidity [or sickness] is also "U-shaped" in the sense that both very short sleep and very long sleep are associated with many illnesses—with depression, with obesity—and therefore with heart disease—and so forth. But the [ideal amount of sleep] for different health measures isn't all in the same place. Most of the low points are at 7 or 8 hr., but there are some at 6 hr. and even at 9 hr. I think diabetes is lowest in 7-hr. sleepers [for example]. But these measures aren't as clear as the mortality data.

I think we can speculate [about why people who sleep from 6.5 to 7.5 hr. live longer], but we have to admit that we don't really understand the reasons. We don't really know yet what is cause and what is effect. So we don't know if a short sleeper can live longer by extending their sleep, and we don't know if a long sleeper can live longer by setting the alarm clock a bit earlier. We're hoping to organize tests of those questions.

One of the reasons I like to publicize these facts is that I think we can prevent a lot of insomnia and distress just by telling people that short sleep is O.K. We've all been told you ought to sleep 8 hr., but there was never any evidence. A very common problem we see at sleep clinics is people who spend too long in bed. They think they should sleep 8 or 9 hr., so they spend [that amount of time] in bed, with the result that they have trouble falling asleep and wake up a lot during the night. Oddly enough, a lot of the problem [of insomnia] is lying in bed awake, worrying about it. There have been many controlled studies in the U.S., Great Britain and other parts of Europe that show that an insomnia treatment that involves getting out of bed when you're not sleepy and restricting your time in bed actually helps people to sleep more. They get over their fear of the bed. They get over the worry, and become confident that when they go to bed, they will sleep. So spending less time in bed actually makes sleep better. It is in fact a more powerful and effective long-term treatment for insomnia than sleeping pills.


In another report:-

The term sleep disorder may suggest someone tossing and turning all night, but lying awake for hours with insomnia is just one example of many conditions that affect how you sleep and function during the day. In fact, you can have a sleep disorder and not even know it.

How many hours should you sleep?
There's no normal number of hours that quantifies a good sleep, just like there's no normal shoe size. Most adults need seven to nine hours a night; others manage just fine with six. It's even possible to get too much sleep, since spending excess time in bed can be a sign of another health problem, such as depression or chronic fatigue syndrome.

A 2007 British study found that people who slept the same amount of time (seven hours) each night lived longer, on average, than people who adjusted their schedules to either add or subtract hours from their nightly slumber. Finding your own ideal sleep/wake cycle—and staying consistent—is key to healthy sleep, agrees Carol Ash, DO, medical director of the Sleep for Life center in Hillsborough, N.J.

Don't sell yourself short
That doesn't mean you can shave off hours of much needed rest without consequence: In a different study, the same British scientists also found that people who are consistently sleep deprived (defined as sleeping five hours or less a night) are at greater risk for high blood pressure and cardiovascular problems—especially women.

Insufficient sleep also raises your risk for obesity, diabetes, depression, alcoholism, and automobile accidents. Plus, a 2007 University of California–Berkeley study confirmed the obvious: Sleep deprivation directly affects areas of the brain that deal with mood and concentration, leaving tired people grumpy, overly emotional, and unable to focus.

Consider quality and quantity
For all these reasons, doctors need to look at both the quantity and the quality of sleep to detect a problem. And when it comes to sleep quality, problems aren't always obvious to patients themselves: An insomniac who lies awake at night can easily tell that something is wrong, for example, but someone with sleep apnea—who repeatedly stops breathing in his sleep—might have no idea there's a problem.

The most telling sign of a disorder is how you feel during the day. If you generally wake up alert and refreshed, you're a healthy sleeper. If you chronically wake up sleepy, irritable, and unfocused—and stay that way throughout the day—you may have a sleep disorder, no matter how much time you spend in bed.