Is daylight saving time bad for your health? Mostly in spring. Heart attacks rise about 5% in the week after clocks jump forward (Meta-analysis), and fatal US crashes rise about 6% (Study). Neither shows a clear rise when the clocks go back in autumn. This year that happens on 25 October in Europe and 1 November in the US.
What Daylight Saving Time Is
Daylight saving time (DST) means setting clocks one hour ahead for the warmer months. Sunrise and sunset then both come an hour later by the clock. Standard time is the rest of the year, which Europeans often call winter time. In 2026, Europe goes back to standard time on Sunday 25 October. The US follows on Sunday 1 November. In spring the clocks jump forward again, and most people lose an hour of sleep that night.
One hour matters because your body clock sets itself by daylight, and dawn is one of its main cues. A Munich team tested whether that inner clock keeps up when the clocks change. They surveyed about 55,000 people. Under standard time, sleep on days off moved with dawn as the seasons changed. Under DST, it did not (Study).
The same team then followed 50 people for eight weeks around each change. Their sleep and activity adjusted to the autumn change with little trouble. After the spring change, the timing of their daily activity did not catch up in the weeks they were tracked. Night owls struggled most (Study).
A later review from the same group argues that the two changes are not equal and opposite. Measured against your alarm clock, the spring jump undoes three or more weeks of earlier sunrises, depending on where you live (Review). For heart attacks, the authors add, spring’s harm and autumn’s relief do not cancel out for any one person (Review).
Why Spring Is the Bad Shift
When people say clock changes kill, they mostly mean the spring change. The broadest review so far, from 2026, covered 157 studies from 36 countries. It linked the spring jump to more heart attacks and more fatal traffic accidents (Review). The traffic link was clearest in the US.
A 2019 meta-analysis, which pools the results of earlier studies, looked at heart attacks. It combined 7 studies with more than 115,000 people. Heart attacks rose about 5% in the week after the spring change (Meta-analysis). The week after the autumn change showed no clear rise. A larger 2024 update pooled 12 studies from 10 countries. It found about 4% more heart attacks after spring and no clear change in autumn (Meta-analysis). Those studies disagreed with each other quite a bit, so the authors only say the risk “may” be higher after spring.
Fatal traffic crashes rise too. US researchers looked at 732,835 fatal crashes from 1996 to 2017. The risk rose 6% after the spring change, most of all in the morning and in the western part of a time zone (Study). People at that western edge already sleep about 19 minutes less a day, says a summary from the researchers’ university. It puts the toll at about 28 extra traffic deaths a year in the US (Press release). The extra risk faded over the following week. The autumn change had no effect on fatal crash risk (Study).
Lost sleep may be part of the reason. A 2025 review of 27 studies covered people aged 6 to 85. It linked the spring change to shorter, poorer sleep and more sleepiness during the day (Review). Night owls seemed to be hit hardest. Still, the studies were mixed, and the authors say firm conclusions are hard to draw.
At one high school, 35 teenagers wore wrist trackers around the spring change. They slept 32 minutes less a night, or 2 hours and 42 minutes less over the school week (Study). Their reactions got slower, and their attention lapsed more often.
On the Monday after the spring change, US workers slept about 40 minutes less (Study). In separate records, US miners had more injuries on those Mondays than on other days, and the injuries were worse. After the autumn change, neither sleep nor injuries changed (Study).
Keep these numbers in proportion: they are short bumps that fade within days or weeks. A US study of nearly 14 million deaths found no clear rise in total deaths in the eight weeks after the spring change (Study). It counted deaths by the week, though. A spike lasting only a day or two could slip past it.
Why Autumn Looks Gentler
Autumn gives you an hour back, and the data mostly look better. The 2026 review linked the autumn change to fewer deaths and fewer workplace accidents (Review). It also linked autumn to more violent crime, and spring to less. The link to fewer deaths rests on only three studies. Only about one in five of the review’s studies was rated high quality, so the authors call the evidence limited.
The largest single study is the US one mentioned earlier. It covered 13.9 million deaths from 2015 to 2019. In the eight weeks after the autumn change, deaths from any cause dipped slightly (Study). The authors put that at roughly 10,000 fewer deaths a year across the country. The dip was larger in people aged 75 and over. With both changes counted together, the study found no overall change in deaths. It only observed what happened, so it cannot prove the clock change caused the dip.
You may also have seen a European study claiming that clock changes shift death rates. Its journal withdrew the paper in May 2026, saying the main finding was not properly supported (Retraction). The authors disagree with that decision.
Autumn still has a downside. A Danish study looked at 185,419 hospital contacts for depression from 1995 to 2012. New hospital diagnoses of depression rose about 11% after the autumn change, then faded over about 10 weeks (Study). Spring showed no such rise. The authors suggest the sudden earlier sunset may be to blame, since it signals months of short days ahead.
That finding has limits. It counted only hospital cases, so it missed people treated by their family doctor. It is also one study from one northern country, and it shows a link without proving a cause. Across all its studies, the 2026 review found no consistent effect on mental health (Review).
Strokes are another concern. A Finnish study looked at strokes caused by a blocked artery from 2004 to 2013. Hospital admissions for these strokes rose about 8% in the first two days after a clock change (Study). The study lumped spring and autumn together. Over the full week, the rise was small enough that chance could explain it. People over 65 had a higher risk in those first two days.
Which Permanent Clock Is Healthier?
Major sleep societies want the twice-yearly switch to end, but people disagree about which clock to keep.
A Stanford team built a computer model of the body clock for every US county. They used it to predict obesity and stroke rates (Study). For early birds and night owls alike, switching twice a year strained the body clock more than either permanent option. Permanent standard time came out best for most people, though early birds did slightly better on permanent DST. Stanford’s own summary says permanent DST would bring about two-thirds of the predicted drop in obesity (Press release).
The headline about 300,000 fewer strokes comes from this model, not from counting real strokes. The model compared permanent standard time with today’s switching. It predicted that the share of adults who have had a stroke would fall by about 9 in every 10,000 (Study). Across the US, the paper turns that into roughly 300,000 fewer people. Stanford’s press release said “per year,” but the paper gives no time frame (Press release).
The model also assumed tidy habits, the same under every clock option. Everyone in it slept from 10 pm to 7 am in the dark. At work they sat in office light, and in the evening they had dim indoor light. In 2026 the authors fixed a coding error that let simulated sunlight linger after sunset (Correction). The error affected every run of the model, and the correction notice gave no updated results. Replying to critics, the authors stressed that their results do not prove cause and effect (Reply).
Supporters of permanent standard time point to morning light. The American Academy of Sleep Medicine wants the US to stop changing clocks and keep standard time all year (Statement). It says standard time fits the body clock best. The British Sleep Society takes the same view for the UK. It notes that under permanent DST, the winter sun in Glasgow would not rise until 9:45 am (Statement). The US tried year-round DST during the 1970s oil crisis. Congress reversed it after a single winter (Statement).
The other side points to evening light. A study of about 23,000 children in 9 countries found they moved a bit more on days with later sunsets (Study). They got about 6 more minutes a day of brisk activity when the sun set after 9 pm than when it set before 5 pm. The link showed up mostly in the European and Australian children, not in the American or Brazilian ones.
The 2026 review also found early signs that summers on DST may come with slightly fewer deaths and traffic accidents. Each of those findings rests on a single study, though (Review). The British Sleep Society accepts that evening light may have upsides, such as more time for exercise. It judges that the costs to sleep outweigh them (Statement).
The 2026 review did not take a side on keeping or scrapping the clock changes. It called for a balanced approach instead (Review). It did note that if the changes end, the sleep evidence leans toward permanent standard time.
In the US, a bill called the Sunshine Protection Act would make DST permanent. The House passed it by 308 votes to 117 on 14 July 2026 (Roll call). As of early October, it sat in a Senate committee with no vote scheduled. Critics in the Senate, including Senator Tom Cotton, warn of very late winter sunrises (Report).
How to Handle the Clock Change
You can plan for the weekend the clocks change. This builds on two habits we have covered before: keeping a regular sleep schedule and getting morning light for your body clock. The aim here is narrower: getting through one rough week.
The main tool is the timing of your light. Lab tests gave people long sessions of bright light. Light after the body’s overnight low point moved the body clock earlier. Light before that point, in the evening and early night, moved it later (Study).
For the autumn change, you have two easy options. One is to go to bed and get up 15 to 20 minutes later each night for three or four nights before the change. The other is to wake at your usual time by the new clock from the first morning. If you start waking too early, get some light in the evening to nudge your clock later (Study). Once your sleep settles into the new times, go back to your usual morning daylight.
Then keep an eye on your mood as the dark evenings set in. In the Danish data, the rise in depression lasted about 10 weeks (Study). If low mood hangs on, talk to someone you trust or see a doctor.
Spring takes more work, because you have to go to bed earlier. Move your sleep earlier in small steps over the days before. Then get bright light as soon as you wake up. A lab trial tested this pairing in 28 young adults, split into three small groups. They moved their sleep an hour earlier each day for three days. With steady bright morning light, their body clocks moved about 2 hours earlier. In dim light, they moved just over half an hour (Trial). The trial was about jet lag rather than clock changes, so treat it as a rough guide.
Take care on the road, too. After the spring change, the extra fatal crashes cluster in the morning (Press release). In autumn the risk shifts later in the day. As darkness came earlier, morning crashes fell and evening crashes rose, so the two roughly cancelled out. If you feel drowsy on the Monday after a change, let someone else drive if you can.
Some people need more care than others. Night owls seem to take the spring change hardest, though the studies are mixed (Review). Teenagers lose sleep too (Study). If you have heart disease, you may want to protect your sleep that week, since heart attacks tick up then. In the Finnish data, adults over 65 had a larger rise in strokes in the two days after a clock change (Study).
Frequently Asked Questions
Does Daylight Saving Time Kill People?
Probably not in a large or lasting way. The spring change comes with small, short rises. Heart attacks go up about 5% in the following week (Meta-analysis), and fatal US crashes about 6% (Study). A study of nearly 14 million US deaths found no clear rise in total deaths after spring, and a slight dip after autumn (Study).
Daylight Saving Time vs Permanent Standard Time?
It comes down to morning light versus evening light. Major sleep societies favor permanent standard time, saying it fits the body clock best (Statement). Permanent DST gives more evening light, which is linked to children being a bit more active (Study). A Stanford computer model found that either permanent option put less strain on the body clock than switching twice a year (Study).
Is Daylight Saving Time Going to Be Permanent?
Not yet. The US House passed the Sunshine Protection Act by 308 votes to 117 in July 2026 (Roll call). As of early October, the Senate had not voted, and no vote was scheduled (Report). So US clocks are still due to go back on 1 November 2026.
Does Daylight Saving Time Make It Dark Earlier?
No, ending it does. When daylight saving time ends in autumn, sunset comes an hour earlier by the clock. The day still has the same amount of daylight. That sudden dark evening may matter. Danish hospitals saw about 11% more new depression diagnoses after the autumn change (Study).
Is Daylight Saving Time Bad for Your Health Long Term?
The evidence is thin and points both ways. Body clock researchers found that sleep timing does not fully adjust to DST over the summer (Study). Yet the 2026 review found early signs that summers on DST may come with slightly fewer deaths and traffic accidents. Each of those signs rests on a single study, and the authors call the evidence limited (Review).
Key Takeaways
- Spring is the risky shift: Heart attacks rise about 5% in the week after clocks jump forward (Meta-analysis), and fatal US crashes rise about 6% (Study).
- Autumn is gentler, not harm-free: US deaths dipped slightly after the clocks went back (Study). In Denmark, new hospital diagnoses of depression rose about 11% as evenings turned dark (Study).
- Either permanent clock beats switching, in a model: A Stanford computer model found less strain on the body clock under either option. Standard time came out best for most people (Study).
- The 300,000 strokes figure is a prediction: A computer model estimated a drop of about 9 in every 10,000 adults. It was not a count of real strokes (Study).
- Shift gradually and time your light: In a small lab trial, bright morning light moved body clocks about 2 hours earlier in three days (Trial).
Use the Extra Hour Well
This autumn’s change is the easy one. You get an hour back, and the big studies found no clear rise in heart attacks or fatal crashes after it. Ease your bedtime later over a few nights, and get some evening light if you wake too early. Drive with care as the evenings get dark.
Then mark the spring change in your calendar now. That is the weekend to protect your sleep, especially if you are a night owl or live with a teenager. The argument over a permanent clock will likely keep going. When it comes up, ask what each side gives up: brighter mornings or brighter evenings.
One hour will not make or break your health, but a little planning makes the week after it easier.
This article is for educational purposes and is not medical advice. Talk to a qualified clinician before changing your health regimen.
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