Chronotypes: Are You an Early Bird or a Night Owl?

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Are you a morning person or a night owl?

Longtime readers of this blog would likely say that the answer to that question depends on several factors: how much light exposure you get during the day, how much light exposure you get at night, how your cortisol fluctuates throughout the day, how much coffee you drink and when you drink it, or what time you go to sleep. The best part is that they’re all modifiable. By changing them, we can change how we feel in the morning, how productive we are at certain hours, and whether we need that extra cup of coffee in the afternoon. We are not at the mercy of powers unbeknownst to us. We hold the power.

But is that the whole story?

Probably not. A growing body of research has identified something called a chronotype: a sleep phenotype, determined by slight alterations to the “Period 1″ gene, that influences your sleep and wake time. Genetic early birds have an AA nucleotide base and will be naturally inclined to go to bed and wake up earlier. They make up roughly a third of the population. 16% of people are genetic night owls with a GG nucleotide base; they tend to have later bedtimes and wake times (about an hour after the early birds). And the middle ground – which is almost 50% of people – have an AG base and a tendency to wake up “between” the two extremes. You can affect your sleep habits by changing things like light exposure at day/night, electronic media consumption, caffeine intake, and so on, but the genetic chronotype will always underline your response. It’s the baseline, and recent evidence in live humans confirms this.

You know how when we mention epigenetics, we usually refer to modifiable environmental factors affecting gene expression? The food we eat, the exercise we get, the thoughts we think, the stressors we encounter – these can all modify the function of our genes and we in turn can modify our exposure to them. But here, it’s the actual genetic chronotype that’s affecting how our genes express. It appears that the genes regulating sleep cycles are being modified by the chronotype itself, a kind of internal, self-contained epigenetic input that we cannot directly or consciously alter. Some might see that as a loss of power in determining our fate, but I think it’s a really interesting concept, an additional wrinkle to the broadening story of gene expression.

What does this mean for your health?

Well, mornings tend to be tough for folks with the night owl chronotype. That’s to be expected, since going to bed later than society expects while having to wake up earlier than your biology “wants” means inadequate, lower quality sleep. We all know how a night of poor sleep feels. Imagine a lifetime!

But that’s not all. A quick trip through the literature reveals numerous connections between the night owl chronotype and poor health outcomes. It all seems quite dire:

Why would a chronotype that confers a higher risk of just about every negative health malady be selected for by evolution? How did the GG nucleotide even survive?

Because it’s only in a society with a standard universal workday that begins at around 8 AM that the night owl is an unhealthy, lazy malcontent worthy of our disdain. For every one of the “negative health effects of being a night owl chronotype,” I can link it directly to a lack of sleep:

Poor glucose tolerance? A lack of sleep will lead to it.

Fibromyalgia? Strongly linked to a lack of sleep.

Unhealthy eating? A bad night’s sleep makes junk food more enticing.

Prone to depression? Bad sleep could be causing it.

Thousand of years ago, the night owl would have been the lookout man, the nighttime raider, the drummer around the fire, the shaman who stayed up all night accepting patients. He would have been privy to the same ancestral environmental cues as everyone else – daylight, absence of light at nighttime, whole real foods, plenty of vitamin D – but his chronotype would have pushed his bedtime back a bit and he wouldn’t have been any worse for wear. He didn’t have to get up to beat rush hour or satisfy society’s arbitrary notion of a workday schedule. He could sleep in; he wasn’t getting fired or evicted or forced to get inadequate sleep just to satisfy society’s expectations.

The early bird had a role, too, of course. He’d get up at dawn, or just before it, to get a jump on the game. To stake out a good spot at the watering hole or the feeding grounds.

They are genetic outliers, but we need outliers. The tribe with a blend of early birds, night owls, and in-betweeners would have a better shot at surviving and thriving than the tribe with a perpetual case of the Mondays or the tribe who just can’t stop yawning after dark with the lookouts who fall asleep at their posts.

Nowadays, late chronotypes often suffer from social jetlag: an often permanent misalignment between the demands of their biological clock and the expectations of society. This misalignment even shows up in MRI scans, with night owls having malfunctioning white matter in the “sadness” and “depression” areas of the brain. “The world” assumes an early chronotype. Early risers get the accolades, the job offers. Work schedules revolve around early risers.

It’s no wonder that late chronotypes have all sorts of negative health effects normally associated with poor sleep – they live in a society that forces them to go to bed earlier than they want and wake up earlier than they’re meant to! Social expectations conspire against them.

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