How Much Sleep Do You Really Need?

This week, let’s ask the million-dollar question: How much sleep do you really need?

We all know sleep is important. Shakespeare called it the “sore labor’s bath, balm of hurt minds, great nature’s second course, chief nourisher in life’s feast.” Less poetically, headlines these days seem to be shouting: “Sleep deprivation will make you slower and dumber!” “It will give you Alzheimer's disease and heart attacks!” One mattress advertisement I saw simply said, “You can only live seven days without sleep.” Yikes. Talk about pressure to perform!

Fear-mongering aside, there is good evidence that sleep is important for health, well-being, and performance. A recent meta-analysis including over 1600 participants confirmed that sleep restriction is associated with poorer attention and thinking. We’ve known for decades that sleep deprivation disrupts mood. For example, it can trigger manic episodes in those with bipolar disorder. And we’re learning now, from researchers in Sweden and Germany, that insufficient sleep can even affect the microbiota in your gut.

How Much Sleep Is Enough?

But how much sleep is enough? Is there such a thing as too much sleep? If you ask Dr. Google, you’ll get over a billion answers. (That’s right; “billion” with a “b.”) The most common answer seems to be “eight hours.” That seems pretty straightforward. But where does this number come from? And if you’re thinking, “Dr. Google hasn’t examined me; how would she know how much sleep I need,” then you’re asking exactly the right question.

We’ll get to some tips and answers to the deepest sleep mysteries in a moment. But first, consider this:

We’re often told that we should drink eight glasses of water per day. (It seems like eight is a magic number). But does that apply to everyone? I’m a petite couch potato. Do I really need the same amount of water as, say, soccer phenomenon Megan Rapinoe? Does Ruth Bader Ginsberg need the same amount of water as The Rock? Actually, that’s a tough one … with the way she works out at the gym, RBG really might need that much hydration. In any case, how much water she needs to drink depends on her body’s physiology, her current activities, and other factors.

We can apply the same logic to sleep. How much sleep we need depends on how we are biologically hardwired and on our body’s...

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