Did you remember to change your internal clock with Daylight Savings?

I consider myself a morning person, and am always a little sorry the morning of the March daylight savings time change. I feel like somehow, having woken up so many mornings in the dark that I have “earned” those sunrises and to have them abruptly taken away on Sunday feels like a rip-off. Otherwise, I hardly notice the change because I hardly ever know what time it is anyway.

But that’s where I’m wrong. Even though I don’t consciously perceive it, each sunrise is unconsciously sending signals via light-sensitive cells in my eye back to my brain that put my circadian rhythms in sync with the break of daylight and the setting of the sun. Circadian rhythms are changes in gene and protein expression that vary throughout the day that help your body keep time. They control sleepiness, alertness, hunger and hormones. They are responsible for changes in body temperature and surges of glucose. Outside of the TSA and flight delays, they are what make international travel so dang hard. And, it’s why you might have had trouble going to sleep after you changed your (external) clock this week.

This is not my area of expertise, but I find it fascinating. For an approachable discussion of circadian rhythms by people who know what they are talking about, try this podcast or maybe this less formal one.   Or, if you are so inclined and bothered by my lack of citations, here’s nice scientific review article for you.

Probably because I have been reading a lot of science fiction lately, it makes me wonder just how adaptable our circadian rhythms are. They are amazingly flexible—which is why you can travel to the other side of the planet and adjust to that timezone—but also inflexible in that it takes time to make this adjustment (about a day) and in the absence of other signals (like light) people still generally have about a 24 hour circadian rhythm. My limited understanding of this is that the rate at which the genes and proteins involved in these clocks get expressed, made, and destroyed during this timeframe is roughly equivalent to 24 hours.

So…if you moved to a planet with a 32 hour light-dark cycle would you adjust to it? Or would you end up recreating a 24 hour Earth day on another planet?   Some people claim to have longer or shorter “rhythms” anyway and so maybe it wouldn’t be a big deal.  But, I would argue that extensive studies in shift workers and in people whose clocks are artificially set out of whack (by being placed in isolation rooms with odd light cycles) seems to indicate that this ultimately wouldn’t work well. At least in these groups, it looks like body chemistry changes so that systems don’t work as efficiently.  Also, there are strong links between altered circadian rhythms and obesity, diabetes, disorders like depression, and even neurological diseases (including Alzheimer’s—but it is still unclear whether altered rhythms cause the disease or the disease causes the altered rhythms).    Of course how much of this is something we are born with and something we gain with age? After all, babies are notorious for not having set circadian rhythms and the 24 hour sleep-wake cycle only seems to emerge with development. So maybe if you were born on another planet you might be better adapted and protected from some of the effects of change that we experience here?

I don’t know the answer to these questions. But if you’re still thinking about how much you hate the time change, think instead about how cool it is we all share the experience of having our internal circadian rhythms forced out of sync biannually.

And then think about how we can do away with this dumb daylight savings thing.



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