06/26/2015 12:30 pm ET Updated Dec 06, 2017

Does Your Birthday Determine Your Bedtime? (Maybe)


My birthday, August 19, 1986, shortly after six in the morning, makes me a Leo. A rising Leo, at that. Astrologically speaking, I should be a Super Leo, but, based on what I’ve read, I’m actually a shitty Leo.

To astrology folks, my sign should inform my personality, predilections, even my destiny. Even some scientists surmise that my Leo’ness matters, specifically in setting my preferred bedtime. But, they haven’t been able to confirm the hunch.

In a recent public health study out of China, researchers collected data on sleep preferences from nearly 4,000 Chinese adults, looking for a link between gender, birth month and bedtime. Gender, as it turned out, mattered: Men went to bed later and slept fewer hours than women. Obviously, this isn’t a biological gender issue, strictly speaking. Especially in China, gender is connected to countless lifestyle factors that affect how and when men and women sleep.  

Month of birth, on the other hand, did not matter. On its face, the data showed women born in autumn going to bed later than their winter-born counterparts. But once researchers adjusted the results for confounders, seasonal differences evaporated.

In theory, researchers had good reason to look for a birthday-bedtime connection. Our chronotypes — whether we’re morning larks or night owls — depend both on biological and environmental factors. One theory, first proposed in 1999, claims that the duration of daylight (or, “photoperiod”) at birth affects our chronotypes.

A 2011 study conducted by Italian psychologists compared subjects born in opposite hemispheres, and found more night owls born during seasons with longer photoperiods (spring and summer). More early-risers were born during the short, SAD-inducing days of fall and winter.

Although this connection did not bear out in the Chinese population survey, plenty of scientists think there’s something to be learned. Personally, I’m still not on-board with astrology, but I am starting to believe that I was, indeed, destined to be a night owl from birth. Perhaps this is a rare instance where science could catch up to a long-standing folk belief.

-- Theresa Fisher

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