Sleep Chronotypes
May 11, 2024
Health
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Welcome to The Long Haul! Every week, I’ll explore a longevity topic and then give a roundup of the big news in longevity.
Writing about longevity was all fun and games until I realized something I do is really not good for me...
I think I have to stop being a night owl.
(By the way: Want to get your message in front of 3000 health nuts? Sponsor an issue of the Long Haul! Email robyn@girdley.com)
The TL;DR
💤 Being a morning or evening person (AKA your “sleep chronotype”) is a part of your natural body clock
⚕️ It’s not just when you sleep — your chronotype impacts body temperature, hormonal secretion, food intake, cognitive function & physical performance
🦉 Night owls have greater all-cause mortality and a bunch of other risk factors
🛟 Slight changes to sleep, diet, and exercise can change your sleep chronotype (see the colorful table at the bottom!)
Today's Topic
Sleep Chronotypes
What is a sleep chronotype?
We all have a sleep chronotype, a preference towards when you like to sleep and wake in a day.
The chronotypes are on a spectrum, but generally, everyone fits into one of three categories:
Based on what type you are, your body secretes hormones that keep you awake or make you tired at different times during the day:
Early bird: waking up energized at 6 am, your cortisol (stress hormone) peaks earlier, and by 9 pm your body is already producing melatonin making you tired
Night owl: 8 am is your least favorite time of day, your cortisol peaks later, and you don’t begin to feel tired until 11 pm
The good news is sleep chronotypes affect sleep timing, but not quality or duration. [2]
How to find your sleep chronotype
You probably have a pretty good idea of which one you are already.
But if you want to get specific, this 5-minute, 19-question quiz will show you:
https://qxmd.com/calculate/calculator_829/morningness-eveningness-questionnaire-meq
What does sleep chronotype impact
Your sleep chronotype impacts several bodily functions:
Sleep times
Body temperature
Hormonal secretion
Food intake
Cognitive function & physical performance [1]
And chronotypes typically change as we age:
Young children are morning types
Adolescents are evening types
Most people return to morning types as adults [3]
But that isn’t set in stone. About 60% of adults sit in the middle of the spectrum. The other 40 have a more drastic chronotype. [1]
For most people, their chronotype doesn’t matter all that much. But for the evening types — I’ve got some bad news.
Why evening types suffer
For us night owls, the timing of society is stacked against us. Even the CDC knows it, releasing a report in 2022 saying high school starts too early for teens (commonly night owls).
If life starts between 8-9 am and evening types don’t sleep until 1 am, they don’t get the recommended 7-8 hours of sleep per night. This is reflected in health outcomes.
Night owls have greater all-cause mortality and a slew of other “health hazards”: [4]
Researchers believe the health of evening types could be compromised by a misalignment between their biological clocks and social activities. There’s also evidence that alterations to circadian timing are linked to disease development. [2]
How to fix it
Genetics only account for 50% of the reasoning behind sleep chronotype. This means there’s room to change habits to alter chronotype. [5]
A study took 22 people who were evening types and found that simple lifestyle changes “altered” their sleep chronotype.
After 6 weeks they observed:
Decreased stress & depression
Grip strength peaked earlier in the day
Cognitive performance improved
Melatonin onset advanced by 2 hours (they were sleepy at 10 pm instead of midnight)
Peak cortisol advanced by 2 hours (they were most awake at 9 am instead of 11 am) [6]
How’d they do it? Nothing fancy. This was their routine:
Personally, I’m going to make this my new routine and try to become a reformed night owl. And if you’re already somewhere else on the chronotype spectrum — I have no notes.
The Haul: What you can’t miss in longevity this week
News
Equinox launches a longevity membership: For a cool $40,000/year Equinox can be your one-stop longevity shop
Yogurt doesn’t lower diabetes risk: The FDA now allows yogurt producers to print on containers that yogurt can reduce the risk of Type 2 diabetes. This isn’t exactly true:
Danone, the yogurt manufacturer, asked the FDA for clearance to say this in 2018
The FDA allows it as a “qualified health claim” meaning it lacks full scientific support
They’re permitted to put the claim on the packaging as long as there’s a disclaimer on the package
Research
The optimal way to spend your day to reduce heart disease and diabetes: A 2000-person study found sitting for only 6 hours a day reduces health risks
Thanks for reading.
– Robyn
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8063933/
[2] https://www.nature.com/articles/s41467-018-08259-7
[3] https://journals.sagepub.com/doi/10.1177/2158244017728321
[4] https://link.springer.com/article/10.1007/s40675-015-0022-z
[5] https://academic.oup.com/sleepadvances/article/2/1/zpab016/6400030
DISCLAIMER: None of this is medical advice. This content is strictly educational.