Here Comes the (little) Killer: Daylight Saving Time
Continuing my (and many other people's) campaign against DST
I hate DST.
This may sound odd coming from somebody living at a relatively high latitude, in New York State, (okay, only 41.35 degrees N, approximately), so I should be one of those who loooooooves getting those clocks changed… right?
NO.
NOT GREAT. THANKS FOR ASKING.
So, with the help of my friend Gemini, I’ve got some new stories about the risks that come from the DST switch! Let’s get to it!
HEART ATTACKS
What great timing! There is the whole GO RED (which I always read as GORED) for Heart Health in March, so let’s see this little heart healthy reminder for DST risks!
3 March 2026, University of Alabama, Birmingham: From the expert: The link between daylight saving time and heart attacks
Many people may groan about losing an hour of sleep this spring, but there may be a more serious reason to be mindful of daylight saving time.
Martin Young, Ph.D., in the University of Alabama at Birmingham Division of Cardiovascular Disease, says springing forward one hour is associated not only with increased accidents, but also increased risk of heart attacks, particularly for people with a history of heart disease.
“Moving the clocks ahead one hour in March is associated with a 10 percent to 24 percent increase in the risk of having a heart attack the following Monday and to some degree Tuesday,” Young said.
Young says many factors may contribute to the increased risk of heart attacks following the beginning of daylight saving time, including loss of one hour of sleep and a misalignment of our internal clock. Every cell in the human body has an internal time mechanism, also known as a circadian clock, which is responsible for driving rhythms in biological processes. These rhythms follow a roughly 24-hour cycle, responding to changes in light and darkness in an organism’s environment.
When these clocks are interrupted or experience a sudden change, there can be several different health effects.
“Going from a sleeping state to waking is already a stressful event in the body,” he said. “When we have an abrupt change, like losing an hour of sleep with daylight saving time, our internal clocks don’t have enough time to reset various biological processes.”
Given there is no real benefit from stealing one hour from us IN MARCH (if you want to do it the Sunday before Memorial Day, okay, why not)… HEY GUYS, MAYBE STOP IT.
To ease the transition, he suggests dividing up the one-hour loss over the course of the weekend. For example, if you usually wake up at 6 a.m. on a weekday, then set your alarm for 5:40 a.m. Saturday, for 6:20 a.m. (new time) Sunday and for 6 a.m. Monday. In addition, eat a decent-sized breakfast, then go outside in the sunlight and exercise, as appropriate and as recommended by your doctor.
I’ve got a recommendation:
LET’S STOP HAVING DST
Or, as a compromise, let’s actually start it in May (I mentioned Memorial Day as a great day for starting) and end on Labor Day. Then we’ll have minimal disruption.
MEDICAL MALPRACTICE
These researchers looked at three decades of medical malpractice claims to see if DST had any effect.
Let’s check.
Journal of Clinical Sleep Medicine, 2024 Jun 1: Medical malpractice litigation and daylight saving time
Methods:
We analyzed 288,432 malpractice claims from the National Practitioner Data Bank. To investigate the acute effects of spring DST transition, we compared medical malpractice incidents/decisions 1 week before spring DST transition, 1 week following spring DST transition, and the rest of the year. To investigate the chronic effects of DST months, we compared medical malpractice incidents/decisions averaged across the 7–8 months of DST vs the 4–5 months of standard time.
Results:
With regard to acute effects, spring DST transitions were significantly associated with higher payment decisions but not associated with the severity of medical incidents. With regard to chronic effects, the 7–8 DST months were associated with higher average payments and worse severity of incidents than the 4–5 standard time months.
Now, this seems less a DST issue and more a seasonal issue of people goofing off in summer.
[Okay, maybe I’m being a little dismissive here… but remember, I am biased to begin with. BIASED AGAINST TORT LAWYERS.
Okay, and biased against bad experimental design.]
Do you notice how long the “DST” period is compared to “ST”?
HOW CAN IT BE “STANDARD” TIME WHEN IT’S SHORTER?
Yes, to be serious for a moment, one of my big beefs with DST is that it was extended too long. This is ridiculous.
Okay, maybe Memorial Day to Labor Day is too short if you’re going to have DST…. but SURELY you can see the current version is too long?
So I don’t think this research paper proves anything re: DST. It looks iffy.
But it has a nice figure, which helps to remind people that DST IS TOO DAMN LONG.
TRAFFIC ACCIDENTS
Okay, a lot is going on here.
First off, thank you, sleep medicine professionals, for covering me re: DST.
It’s not the sleep issues that I hate DST (from a personal perspective) — I am a super duper early-morning person who regularly wakes up at 3 am during Standard Time, so it’s not like I’m thrown off. I am a strange person re: sleep.
But one hour … not necessarily a big deal from a SLEEP point of view.
But it’s not just SLEEP — it’s also the quality of light in the morning, and because I live in the part of the U.S. where the roads are based partly on where native people tracked deer I GET THE FRICKIN SUN IN MY EYES WHILE I’M TRYING TO DRIVE AT A “REASONABLE” HOUR AND I CANNOT SEE A DAMN THING.
YOU PEOPLE.
DO YOU NOT THINK ABOUT THE ANGLE OF THE SUN COMING UP OVER THE HORIZON, GETTING INTO PEOPLE’S EYES?
YOU ABSOLUTE DONUTS
Okay, fine, getting to the data.
American Economic Journal: Applied Economics 2016, 8(2): 65–91 http://dx.doi.org/10.1257/app.20140100
2016, Austin C. Smith: Spring Forward at Your Own Risk: Daylight Saving Time and Fatal Vehicle Crashes
Daylight Saving Time (DST ) impacts over 1.5 billion people, yet many of its impacts on practicing populations remain uncertain. Exploiting the discrete nature of DST transitions and a 2007 policy change, I estimate the impact of DST on fatal automobile crashes. My results imply that from 2002–2011 the transition into DST caused over 30 deaths at a social cost of $275 million annually. Employing four tests to decompose the aggregate effect into an ambient light or sleep mechanism, I find that shifting ambient light only reallocates fatalities within a day, while sleep deprivation caused by the spring transition increases risk. (JEL I12, Q48, R41)
Okay, that paper is a decade old.
Recall that DST alters the risk of a fatal crash in two ways: reallocating ambient light from the morning to the evening; and disrupting sleep schedules. Despite strong evidence suggesting the importance of ambient light in fatal crash risk (Fridstrom et al. 1995, Sullivan and Flannagan 2002), the implication for net crashes due to DST remains unclear. DST does not alter the amount of light in a day, it simply reallocates it between the morning and the evening.
My dude — do you even drive?
You can have an “ambient light”, but if you’re one of those people who has an almost straight east-west commute (or, I should say, on the path that the sun rises or sets, which isn’t perfect east-west, due to the tilt of the Earth), THEN HAVING POORLY PLANNED HIGHWAYS BECAUSE YOU LIVE IN NEW YORK OR CONNECTICUT might be relevant.
Yes, I’ve covered this paper before.
This is old stuff, but the point is there’s a jump in fatal crashes immediately after the switch.
A more recent paper:
Current Biology, 2020: A Chronobiological Evaluation of the Acute Effects of Daylight Saving Time on Traffic Accident Risk
Highlights
•
Spring DST transition acutely increases fatal traffic accident risk by 6% in the US
•
∼28 fatal accidents could be prevented yearly if the DST transition was abolished
•
Spring-DST-transition-associated fatal accident risk is highest in the morning
•
Locations further west in a time zone are affected more by the spring transition
Summary
There is evidence that the spring Daylight Saving Time (DST) transition acutely increases motor vehicle accident (MVA) risk (“DST effect”), which has been partly attributed to sleep deprivation and circadian misalignment [1–6]. Because spring DST also shifts clock time 1 h later, mornings are darker and evenings brighter, changing illumination conditions for peak traffic density. This daytime-dependent illumination change (“time of day effect”) is hypothesized to result in DST-associated afternoon and evening accident risk reductions [2, 5, 7]. Furthermore, sunrise and local photoperiod timing depend on position in time zone. The sun rises at an earlier clock time in the eastern regions of a given time zone than in the western regions, which is thought to induce higher levels of circadian misalignment in the west than in the east (“time zone effect”) [8, 9]. This study evaluated the acute consequences of the DST transition on MVAs in a chronobiological context, quantifying DST, time of day, and time zone effects. We used large US registry data, including 732,835 fatal MVAs recorded across all states (1996–2017), and observed that spring DST significantly increased fatal MVA risk by 6%, which was more pronounced in the morning and in locations further west within a time zone. DST-associated MVA risk increased even in the afternoon hours, despite longer daylight hours. The MVA risk increase waned in the week subsequent to DST, and there were no effects of the fall-back transition to Standard Time (ST) on MVA risk, further supporting the hypothesis that DST-transition-associated, preventable circadian misalignment and sleep deprivation might underlie MVA risk increases.
Just an FYI, the risk comes just from the switch.
I picked two of the most significant papers. Various data analyses have been done, with various models, etc.
Gemini gave me a summary:
I am popping off at various annoyances, but the research itself shows that the spring DST transition itself leads to extra deadly car crashes (about 6% extra), whether early March or a month later (as it used to be).
Once upon a time, we had no DST… and many countries have no DST. It’s not required.
Just saying.
Prior Posts on DST
11 Mar 2024: DST Kills: More Tales of the Killer Time-Changer
2 Nov 2025: The Week in Meep: All Souls Day, Movember, Obra Dinn, Down with DST
5 Nov 2023: Death to Daylight Saving Time!
9 Mar 2025: The Week in Meep: Death to DST (and not us), Sumo (again), The Little Mermaid
I am SO with you on getting rid of DST!!!