Physiology Friday Issue #5: Permanent Daylight Saving Time is a Public Health Mistake

Brady Holmer
3 min readMar 18, 2022


Hello friends,

Happy Physiology Friday!

Check out the sponsors of this newsletter and their special offers for my audience including:

LMNT electrolyte drink mix (FREE sample pack)

H.V.M.N. Ketone IQ exogenous ketone drink (10% off your purchase)

Still feeling a bit of “jet lag” from the time switch? You’re probably not alone. Our poor circadian rhythms shouldn’t have to put up with a twice-yearly time change. The 1-hour jump back (in the fall) and forward (in the spring) may seem like a benign change of the clocks, but there is plenty of data to support that DST has significant population-wide health effects. For instance, the switch from standard time to DST is associated with more cardiovascular events like heart attack and stroke, mood disorders, car crashes, and workplace injuries.

DST — which shifts the daylight hours to the later part of the day — is also out of line with natural human circadian rhythms. Getting light in the morning is the most important regulator of our circadian rhythm and with DST, we get less morning light and more evening light, which can exacerbate circadian misalignment that is all-too prevalent in society. In short, DST is harmful for public health, and this is something many experts agree on.

Human circadian rhythms:

In fact, the American Academy of Sleep Medicine — backed by dozens of professional scientific societies — published a position statement in 2020 which strongly recommended that “these seasonal time changes should be abolished in favor of a fixed, national, year-round standard time.”

On Tuesday, the opposite happened, when the The Senate unanimously voted to enact permanent Daylight Saving Time.

In response, the American Academy of Sleep Medicine posted another statement opposing what in their eyes was a quick and unscientific decision. While they applauded the move to stop the endless clock-switching, they also argued that the evidence to make DST rather than standard time permanent goes against all available evidence, most of which was cited in their 2020 position statement.

They conclude by stating that “it is time to stop changing the time twice per year. We believe that permanent standard time is the best option for health.”

Whether or not the decision to make DST permanent can be reversed is unknown, but the AASM recommended that government officials take more time to consider this decision and perhaps opt for permanent standard time instead.

It’s confusing to me that we have so many government health authorities who advise public policy based on sound science, yet often their recommendations are ignored. In the case of DST, there is almost overwhelming evidence that the implications for public health are vast. Experts have cited this evidence for decades and used it in their arguments to abolish DST forever.

Fortunately, there are things that one can do to offset the effects of DST on circadian rhythms. A few of these include exposing yourself to morning light as soon as possible and, if not natural light, using some type of artificial light or light-emitting device to set your daily clocks.

Exercise and diet are also huge. Consistent exercise at the same time of day (especially the morning) and food intake are both “zeitgebers” that can help our body “keep time.”

Given enough time, we may all eventually adapt to DST, although there is some evidence that cortisol rhythms may be resistant to changes in clock time, at least for a few months.

While permanent DST may be a boon for those who like to start their day early, it’s also an opportunity for an “extra hour” of light at night to hang with friends, enjoy the weather outdoors, or exercise. Always nice to look at the glass half full.

Thanks for reading. See you next Friday.




Brady Holmer

PhD candidate at the University of Florida — Science writing with a particular focus on exercise and nutrition interventions, aging, health, and disease.