There's a lot of talk about acute risks--what happens a day or two after the time change. Most articles you'll read are all about this.
The second topic, the main one that circadian scientists talk about, is chronic risks, and I believe they are more important to our health. To follow this logic, you have to believe that people will continue doing whatever it is they do today (e.g., going to bed at midnight), and won't shift their schedule around right away to optimize sleep--i.e. they will not recognize that their body clock is set mainly by sunlight. The campaign to change school start times has been going for 25+ years already, so fast changes here are pretty rare.
When the clocks change, people wake up at a different circadian time, and if that time is too early, it is associated with worse health outcomes.
Some large-scale epidemiological tools have been used to figure these things out. One compares the difference between sleep patterns on "work" days and "free" days - like how much do you sleep in on a weekend? (Till Roenneberg's "social jetlag"). A second method uses "position in timezone" - comparing people living on the eastern or western edge of a timezone in various ways.
Roenneberg's work from the mid-2000s showed that night owls suffer a lot under "wake up before the sun" kinds of schedules (their "social jetlag" is bigger) - it makes them fatter, more irritable, get more diabetes, etc. They don't go to bed any earlier, but they're forced to wake up earlier.
Next, when you look at timezone position (this has been done for millions of people), people on the western edge of a timezone (where the sun comes up later but the clock is set at the same time) are quite a bit worse off for cancer rates and obesity - 10-20% more for some kinds of cancers, and a roughly 20% increase in chances of being obese.
I work third shift, but switch to daylight schedules on weekends and trips often. I've just learned to plan my sleep about 24-36 hours in advance, and do anything necessary to ensure I get sufficient sleep before any planned activity (workout/stay up late/sleep short amounts to induce sleepiness at the correct time to get a good, long sleep before engagements). I'm pretty independent of circadian rhythm now. As a side effect, as someone who used to consider themselves a night owl, I now prefer to wake up around sunrise whenever possible (assuming I'll be able to do it for a few days in a row)
It's not like jet lag is a new phenomenon. It's just a bit unfortunate to introduce minor jet lag to the entire population without giving them much chance to adapt.
Yes China should have some of this, but they have also had time to adapt to a fixed timezone.
Most of these curves are U-shaped...
I think generally standard time-1 would "hurt" early birds, and DST/double DST would discriminate against night owls.
The pattern for early birds is they get an invite for a business dinner at 9PM (staying up late) and then they wake up at 4:30AM anyway, so they don't sleep enough when you make them stay up late.
Comments
There's a lot of talk about acute risks--what happens a day or two after the time change. Most articles you'll read are all about this.
The second topic, the main one that circadian scientists talk about, is chronic risks, and I believe they are more important to our health. To follow this logic, you have to believe that people will continue doing whatever it is they do today (e.g., going to bed at midnight), and won't shift their schedule around right away to optimize sleep--i.e. they will not recognize that their body clock is set mainly by sunlight. The campaign to change school start times has been going for 25+ years already, so fast changes here are pretty rare.
When the clocks change, people wake up at a different circadian time, and if that time is too early, it is associated with worse health outcomes.
Some large-scale epidemiological tools have been used to figure these things out. One compares the difference between sleep patterns on "work" days and "free" days - like how much do you sleep in on a weekend? (Till Roenneberg's "social jetlag"). A second method uses "position in timezone" - comparing people living on the eastern or western edge of a timezone in various ways.
Roenneberg's work from the mid-2000s showed that night owls suffer a lot under "wake up before the sun" kinds of schedules (their "social jetlag" is bigger) - it makes them fatter, more irritable, get more diabetes, etc. They don't go to bed any earlier, but they're forced to wake up earlier.
Next, when you look at timezone position (this has been done for millions of people), people on the western edge of a timezone (where the sun comes up later but the clock is set at the same time) are quite a bit worse off for cancer rates and obesity - 10-20% more for some kinds of cancers, and a roughly 20% increase in chances of being obese.
I'm worried about these chronic health problems, so I've been writing and advocating for standard time: https://medium.com/@herf/why-standard-time-is-better-e586b50...
I work third shift, but switch to daylight schedules on weekends and trips often. I've just learned to plan my sleep about 24-36 hours in advance, and do anything necessary to ensure I get sufficient sleep before any planned activity (workout/stay up late/sleep short amounts to induce sleepiness at the correct time to get a good, long sleep before engagements). I'm pretty independent of circadian rhythm now. As a side effect, as someone who used to consider themselves a night owl, I now prefer to wake up around sunrise whenever possible (assuming I'll be able to do it for a few days in a row)
We better stop flying across time zones for work or holiday then, if the impact is this severe.
If you can help it then yes, for the sake of your metabolic health you should decrease the amount of time that you switch time zones.
It's not like jet lag is a new phenomenon. It's just a bit unfortunate to introduce minor jet lag to the entire population without giving them much chance to adapt.
It's not just a bit unfortunate, especially as we learn more about how jet lag isn't just about being tired but also can damage metabolic health.
Would (standard time - 1) be even better? Does the data exist? I think Chinese should have it.
Yes China should have some of this, but they have also had time to adapt to a fixed timezone.
Most of these curves are U-shaped...
I think generally standard time-1 would "hurt" early birds, and DST/double DST would discriminate against night owls.
The pattern for early birds is they get an invite for a business dinner at 9PM (staying up late) and then they wake up at 4:30AM anyway, so they don't sleep enough when you make them stay up late.