If you want to know whether one hour of sleep matters, look at Monday

Clocks moved forward at 2 a.m. this morning and most of the country lost an hour of sleep at once. You cannot run a randomized trial that takes an hour of sleep from three hundred million people, but twice a year a government does it for free, and researchers have been reading the results for decades. In Sweden, heart attacks ran about 5% above expected in the week after the spring change, concentrated in the first three days, with a smaller dip after the autumn change (Janszky and Ljung,New England Journal of Medicine, 2008). In the United States, an analysis of 732,835 fatal crashes over twenty-two years found a 6% rise in the workweek after the spring switch, most of it in the morning, larger on the western edges of time zones where sunrise comes latest, and no net change in the fall (Fritz and colleagues,Current Biology, 2020). About 28 extra deaths a year, from one hour.

Read it as a dose, not a scare. These are population studies; they say nothing about your Monday specifically, and the absolute risks are small. What they establish is the thing the sleep-products industry would rather you learned from a device: a single hour, subtracted from a whole population, is visible in hospital admissions and crash reports. The same hour, subtracted every night by a late bedtime, does not show up in a headline because nobody runs the comparison. The clock change is the only week of the year when the experiment is run for you.

Loree’s take

This is the week I tell patients to be boring. Go to bed when you are tired tonight, not when the new clock says. Leave the car in the garage tomorrow morning if you can walk. The American Academy of Sleep Medicine has said for years that permanent standard time would be better for health than the switch; until the law changes, the switch is a reminder that the cheapest sleep intervention is the hour you give back to yourself.

Ben’s take

No company can sell you the finding above, because there is nothing to buy: the data say an hour matters, and an hour is free. What the industry sells instead is the measurement of the hour — a score, a stage breakdown, a readiness number — which costs money and changes nothing about Monday. If the crash data move you, move your bedtime. It is the only lever in the story.