Is Seven Hours A Night The Optimal Amount Of Sleep?

New research zeroes in on the time you should spend snoozing--but take it with a dose of skepticism.

You're probably not getting enough sleep, but you might not be as far off the mark as you think.

Most sleep experts would offer that aiming for between seven to nine hours of snooze time a night is optimal for feeling refreshed and productive the next day. In a new report, however, the Wall Street Journal writes that researchers are closing in on what may just be that magic nightly number--and it's not nine hours, or even eight as once believed.

According to the Journal, it's seven hours of sleep.

The usual caveats apply, and these findings should be taken with a grain of salt. But the results are interesting--especially if you're the kind of person who struggles with sluggishness throughout the day.

"The lowest mortality and morbidity is with seven hours," Shawn Youngstedt, a professor in the College of Nursing and Health Innovation at Arizona State University Phoenix, told the Journal. "Eight hours or more has consistently been shown to be hazardous."

The report cites one study, published in 2002, that tracked 1.1 million people over a six-year data period for cancer research. The study's administrators discovered that people who slept between 6.5 to 7.4 hours a night generally had a lower mortality rate than people who slept less, and people who slept more. "Previous sleep studies have indicated that both short- and long-duration sleep had higher mortality rates," said Dr. Daniel F. Kripke in 2002. "However, none of those studies were large enough to distinguish the difference between 7 and 8 hours a night."

Some researchers caution against studies that warn people about too much sleep. As the Journal reports, "illness may cause someone to sleep or spend more time in bed," which would confound results that link higher mortality with more sleep.

Of course, that seven-hour figure assumes that people all have the same sleep requirements--that it's one size fits all to feel fit, refreshed, and ready to tackle your day.

It's not.

Sleep is a "spectrum," recommends the National Sleep Foundation, and where ordinary people fall on it depends on a number of different factors:

Not only do different age groups need different amounts of sleep, but sleep needs are also individual. Just like any other characteristics you are born with, the amount of sleep you need to function best may be different for you than for someone who is of the same age and gender. While you may be at your absolute best sleeping seven hours a night, someone else may clearly need nine hours to have a happy, productive life.

Thomas Edison, for instance, managed to stay pretty productive while only sleeping four hours a night. He was also a noted power napper (even keeping a napping cot in his lab), which was useful for overcoming creative roadblocks.

A handful of today's most successful people similarly swear by just a few hours every night: Yahoo CEO Marissa Mayer sleeps four to six hours nightly; fashion designer Tom Ford sleeps just three hours a night; and basketball star Kobe Bryant reportedly practices something called a polyphasic sleep schedule, which allows him to sleep just three to four hours every night, with naps sprinkled throughout the day.

If you want to find the optimal amount of dream time that works for you, try this: Go on vacation. One day--jet lag notwithstanding--go to sleep at a reasonable hour (ideally not drunk!) and wake up the next day without an alarm clock. Feeling good? That should give you a ballpark figure to work with and build your normal schedule around.

And if you just so happen to clock in at seven hours, well, that's great too.

[h/t: WSJ]

[Image: Flickr user AnEternalGoldenBraid]

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