Thomas Edison was known for trying to find workarounds for his notorious need for 10 hours of sleep a night (which has led to some pretty hilarious photos of him napping, literally, everywhere). As smart as he was, and despite the many ways as he tried to overcome it, it seems he was never able to figure out how to reduce his zzzz’s. That’s because, as scientists now know, we are born with biologically determined chronotypes.

What’s your chronotype? Do you even know? (Have you even heard that word before?) Turns out that we all live in a slightly varying world of sleep- and awake-times, though for the most part, the world of schedules, jobs, school and alarms does a good job of convincing us otherwise.

It makes sense that we would all have differing times when we are optimally awake; in preindustrial human history (that is, most of it) it would have made sense to have some people awake and alert late at night, with others awake early in the morning — for information transmission, predator protection and defense against enemies, it would be a boon for any society to have people alert at as many hours of the day and night as possible.

But if you are among the many people who really, really struggle to wake up in the mornings, or conversely, are one of those who does not — an early bird as the folklore puts it — then you are a person with a variable chronotype to the usual. (Check out this great article that explains how scientists figured this out by studying people’s "free sleep" patterns, and then figure out your own.) 

I am a "late riser" from a family of early birds; I was raised by my grandmother and father, who were both enthusiastic early risers. I have never been able to think well before about 10 a.m., though I was always told — and always believed — that I would grow out of it. That one day I would just love the sunrise! But it never happened and so I thought maybe there was something wrong with me. It’s not that I have trouble waking up — I don’t. As long as it’s not too early in the morning. I can get eight hours of sleep from 12:30 to 8:30 and wake up refreshed before the alarm, but if I try to alter that schedule from, say, 10 p.m. to 6 a.m., forget it. (Believe me, I tried for years and I couldn’t get it to stick.) Turns out that my chronotype is one that means my midsleep is probably around 4:30 a.m. — for early risers, midsleep could be many hours earlier. It’s a pretty pervasive social myth that we can all be (or should be) early risers. 

In his book, "Internal Time: Chronotypes, Social Jetlag and Why You’re so Tired," author and German chronobiologist Till Reonnenberg writes, “This myth that early risers are good people and that late risers are lazy has its reasons and merits in rural societies, but becomes questionable in a modern 24/7 society. The old moral is so prevalent, however, that it still dominates our beliefs, even in modern times. The postman doesn’t think for a second that the young man might have worked until the early morning hours because he is a night-shift worker or for other reasons. He labels healthy young people who sleep into the day as lazy.”

In terms of the amount of sleep we need, that's biologically variable too. Just as there are a very few people who need only four or five hours of sleep a night to be healthy (though there are some, we shouldn't all try to be like them), there are just as many who need nine to 10 hours; most of us are somewhere in the middle.

I know I need something more than eight hours of sleep most nights – my sweet spot is almost, but not quite nine hours of sleep a night. I’ve been a happier person since I stopped feeling badly about it and just accepted that’s what my body needs.

How much sleep do you get?

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