Brian Snyder/Reuters
- Daylight-saving time in the US ends on Sunday, November 1, 2020 at 2 a.m.
- That morning, most phones and computers will automatically tick backward one hour, and we’ll win an hour more to sleep.
- But the opposite interruption in the springtime, when we lose an hour of sleep, can kill people: Incidents of heart attacks, strokes, and fatal car accidents all spike around the start of daylight-saving time each year.
- Visit Business Insider’s homepage for more stories.
Daylight-saving time is a killer.
The annual ritual in which we “gain” an hour of evening light in the summertime by pushing the clocks forward, and then descend into darker evenings by pushing the clocks backward in the fall may seem like a harmless shift.
But every year on the Monday after the springtime switch, hospitals report a 24% spike in heart-attack visits around the US.
Just a coincidence? Probably not. Doctors see an opposite trend each fall: The day after we turn back the clocks, heart attack visits drop 21% as many people enjoy a little extra pillow time.
“That’s how fragile and susceptible your body is to even just one hour of lost sleep,” sleep expert Matthew Walker, author of “How We Sleep,” previously told Business Insider.
Yuqing Liu/Business Insider
The reason that springing the clocks forward can kill us comes down to interrupted sleep schedules. This Sunday, November 1, instead of the clock turning from 1:59 to 2:00 a.m., it will repeat the hour, and tick back to 1:00 a.m. (Shift-workers, worry not: federal law mandates you will still get paid for that extra hour of moonlit work.)
That extra hour of rest may seem like good news this Halloween weekend, but over the long haul, the interrupted sleep schedules that result from shifting the clocks back and forth twice a year may be bad for our health.
Researchers estimate that each spring we deprive ourselves of an extra 40 minutes of sleep because of the change. Our bodies may not fully recover from the shift for weeks, though the tragic heart attack trend only lasts about a day.
We’re also prone to make more deadly mistakes on the roads: Researchers estimate that car crashes in the US caused by sleepy daylight-saving drivers likely cost 30 extra people their lives over the nine-year period from 2002-2011. The problems don’t stop there. DST also causes more reports of injuries at work, more strokes, and may lead to a temporary increase in suicides.
Walker said daylight-saving time, or DST, is a kind of “global experiment” we perform twice a year. And the results show just how sensitive our bodies are to the whims of changing schedules: In the fall the shift is a blessing; in the spring it’s a fatal curse.
Why we ‘save’ daylight for the later hours of the day
Daylight-saving time was originally concocted as a way to save energy in the evening, and was implemented during World War I in Germany. But more recent research suggests it’s probably not saving us any megawatts of power at all. There is some evidence, however, that extra evening light can reduce crime and increase the time people spend exercising, at least in certain climates.
Worldwide, fewer than half of all countries participate in this biannual clock-changing ritual.
Not everyone in the US follows it either. Hawaii and Arizona ignore DST, since it makes less sense to shift the clocks when you live near the equator, where the sun rises and sets at roughly the same time every day.
Residents and lawmakers in California and Florida are also trying to ditch the switch. Voters in the Golden State opted to get rid of the annual clock change in the 2018 midterm elections, and Florida lawmakers enacted the “Sunshine Protection Act” that March, aimed at doing the same thing.
Twelve more states have angled to move to year-round DST since then, with proposed legislation. But the shift to a permanent daylight-saving-time plan isn’t something states can decide for themselves: The measures require a green light from Congress to take effect, something both California and Florida, as well as the others (Arkansas, Delaware, Georgia, Idaho, Louisiana, Maine, Oregon, South Carolina, Tennessee, Utah, Washington, and Wyoming) have yet to receive.
So while you might enjoy an extra hour of sleep this weekend, be mindful that the biannual tradition invariably costs some people their lives.
- Read more about daylight-saving time and sleep:
- Why we have daylight-saving time and why 7 states have gotten rid of it or are trying to
- You are probably not getting enough sleep, and it is killing you
- Daylight-saving time is one of humanity’s dumbest rituals, and you should be furious it still happens
- Here’s what sleeping less than 7 hours per night does to your body and brain
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