How Many Hours Sleep Do You Really Need?

How Many Hours Sleep Do You Really Need?

The general rule of thumb for what counts as a full night’s sleep has been eight hours for as long as anyone can remember. Despite this, most of us are happy to get by on less. After all, what difference does an extra hour or two really make? As it turns out, quite a lot. According to science, sleeping even seven hours a night will slowly add up to a costly sleep debt.

Two studies, one at the University of Pennsylvania and another at the Walter Reed Research Institute, tested dozens of sleepers in a bid to find out how much sleep the average human needs. The studies lasted about four years and posted their results back in 2003.

Despite this, most people still operate under the old assumption that five or six hours of nightly sleep is enough to operate indefinitely, without any consequences. While it’s true that a small percentage of people can actually pull it off, the number that most of us need is a rock-solid eight hours — anything less and we begin to suffer major losses in everything from attention span to reaction time.

The participants in the study were tested in a controlled laboratory setting for a period of two weeks. Those who slept eight or nine hours didn’t show any signs of slowing down when tested, but the four and six hour groups were found to be impaired to the point of being “the cognitive equivalent of being legally drunk” at the end of the two-week period. Sleeping in on the weekends won’t necessarily make it better, either. We just need to sleep more.

If you’re having trouble meeting your eight hour quota, here are some tips for sleeping better.

This article has been revised and updated from its original publication date.


  • I only get 5 – 6 hours if I am lucky. I work 3rd shift. It was hard when I first started but after I adjusted to it, it was easy. And I feel well rested about 99% of the time. The times I dont it is because someone has woken me up a few times. Often have nieces and nephews over. It all boils down to your schedule and if you keep on it well.

  • The need for sleeping 8 or 9 hours a night is simply untrue. In that particular study, I’d wager that the participants that were chosen were already people who regularly got 8 hours of sleep a night. If that’s the case, then of course they would show signs after cutting their sleeping times to 5 or 6 hours.

    Many people function quite well on 5 or 6 hours / night. And its because they get 5 or 6 hours of quality sleep.

    You don’t need to sleep MORE, you need to get more QUALITY sleep.

    • I Agree with “ You don’t need to sleep MORE, you need to get more QUALITY sleep”
      The night before an exam I average around 4-6 Hours sleep, Even after ‘Cramming’ for a day and a half. And I still can concentrate the next day.
      Other times where I have say slept at someones house I usually don’t get the Quality of sleep I need as I’m not in the comfort of my bedroom in my snuggly bed, even though I get around 8-10 hours sleep. I can feel drowsy the next day.
      In saying this it really comes down to the person and their unique lifestyle.

      • You replied a minute later. I’m sure your agreement has nothing to do with you being the same person or anything.

        • Not to mention i can do 4-5 hours and wake up feeling great, do that most days for 3 months (like have a baby) and you’ll be quite buggered.

  • These results are in line with other studies that show anything more or less than 8 hours increases the risk of heart conditions in later life.

  • One conceivable reason of dozing is that our muscles need sleep. In any case, you realize that heart is additionally a muscle in our body which doesn’t sleep like other body organs, for example, liver and kidney continue working…

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