Why sleep doctors oppose permanent daylight saving time

Key takeaways

• On July 14, 2026, the U.S. House voted 308 to 117 to make daylight saving time permanent, and the American Academy of Sleep Medicine urged the Senate to reject the bill¹.
• Your master clock is a cluster of nerve cells in the brain, and nearly every organ keeps its own clock in step with it².
• The clock’s gears are genes: the 2017 Nobel Prize honored three Americans who showed, in fruit flies, how a clock protein builds up at night and breaks down by day²³.
• Being a night owl is partly inherited: a 2019 study of 697,828 people found 351 gene regions linked to being a morning person⁶.
• If you sleep far later on days off than on workdays, you have “social jet lag,” which large surveys link to higher body weight, though they can’t prove it is the cause⁷⁸.

On Tuesday, July 14, 2026, the U.S. House of Representatives voted 308 to 117 to end the twice-a-year clock change by making daylight saving time permanent¹. The bill is H.R. 139, the Sunshine Protection Act¹.

The next day, the American Academy of Sleep Medicine (AASM), whose members include more than 9,500 physicians, scientists and other health professionals, pushed back hard¹. “We call on the Senate to reject this dangerous mandate,” said its president, Dr. Fariha Abbasi-Feinberg¹.

Why would sleep doctors fight more evening sunshine? Their case isn’t about the clock on your wall. It’s about the one in your head.

That clock is built from genes. It sets the daily rise and fall of your sleep, hormones, body temperature and digestion, and it resets itself mainly by light². It also explains why some people are wide awake at midnight and why Monday mornings can feel like a red-eye flight.

A Nobel Prize clock made of genes, first found in fruit flies

Circadian rhythms are the physical, mental and behavioral changes your body runs through over about 24 hours². Light and dark shape them most, but food, activity, stress, social life and temperature matter too².

In 2017, the Nobel Prize in Physiology or Medicine went to Jeffrey Hall and Michael Rosbash, longtime Brandeis University scientists, and Michael Young of Rockefeller University for showing what makes the clock tick³. Working with fruit flies, they isolated a gene whose protein builds up in cells at night and breaks down during the day³.

The National Institute of General Medical Sciences (NIGMS), which funded all three, explains the loop². In flies, a protein called PER is made by day but quickly destroyed. At night, a partner protein called TIM protects it, and the pair moves into the cell’s control center and shuts off the making of more PER².

At dawn the pair breaks down, and the cycle starts over². Scientists call this a negative feedback loop. Think of a kitchen timer that rewinds itself every day.

The Nobel Assembly noted that clocks in the cells of other many-celled creatures, people included, follow the same principles³. One quirk matters for daily life. For most people, the natural cycle runs a little longer than 24 hours, according to the National Heart, Lung, and Blood Institute (NHLBI)⁴. Left alone, your clock would drift later, so it needs a daily nudge.

The master clock sits in your brain and listens for light

Nearly all your organs, from liver to gut, keep their own time². A conductor in the brain keeps them playing together. Scientists call it the suprachiasmatic nucleus, or SCN: a big cluster of nerve cells packed into one structure².

Light is its main signal. Light entering the eyes tells the brain it’s daytime, and the SCN uses that message to keep the central clock lined up with the day⁴. Much of this signal travels through light-sensing nerve cells in the retina that contain a pigment called melanopsin, according to a 2022 consensus report by 18 light and sleep scientists⁵.

The SCN then runs your hormone schedule. In the evening it tells the brain to make more melatonin, the hormone that helps bring on sleepiness². Bright artificial light late in the evening can disrupt that rise, and rising morning light prompts a release of cortisol, which helps your body get ready to wake⁴.

Light isn’t the only cue. Meals and activity also send time signals to your body’s clocks². Our companion article on morning light explains how to use daylight on purpose.

Night owls aren’t lazy, but their genes lean late

Your chronotype is your natural timing: whether your body prefers early mornings, late nights or something in between.

Part of it is written in your DNA. In 2019, researchers published a genetic study of 697,828 people from UK Biobank and the company 23andMe in the journal Nature Communications⁶. They raised the number of known gene regions linked to being a morning person from 24 to 351⁶. Many of those genes are active in the retina, the hypothalamus and the pituitary gland⁶.

This is the twist. When 85,760 of the volunteers wore activity monitors, the 5% with the most “morning” gene variants slept only about 25 minutes earlier than the 5% with the fewest⁶. Genes give you a lean, not a fixed schedule. Light, habits and age do the rest.

Age matters a lot. Puberty shifts teens’ clocks, so many prefer later bedtimes and later mornings, while older adults tend to go to bed and wake earlier⁴¹³. A teen who can’t fall asleep at 10 p.m. isn’t simply being stubborn.

The same study used Mendelian randomization, a method that treats inherited gene variants as a natural experiment. It found that being a morning person was linked to better mental health, but not to body weight or type 2 diabetes⁶. That’s one analysis, so treat it as a clue.

Researchers often measure chronotype with the Morningness-Eveningness Questionnaire, which asks when you would choose to wake, sleep, exercise or take a hard test if your days were your own. It’s copyrighted, so we describe it rather than print it. Watching yourself works too.

Find your chronotype: a self-observation guide. This is our own simple method, not a validated test.

1. Pick at least three free days in a row with no alarm, such as a vacation.
2. Each day, jot down when you first feel sleepy, when you fall asleep, when you wake on your own, and when you feel sharpest.
3. Find your free-day midpoint, the clock time halfway between falling asleep and waking. Asleep at midnight and awake at 8 means a midpoint of 4 a.m.
4. Do the same for three workdays with your usual alarm.
5. Compare your notes with the table below.

What you notice on free days	Leans early	In between	Leans late
Waking without an alarm	Early and easy	Mid-morning	Late, and early alarms feel brutal
Sharpest hours	Morning	Late morning to afternoon	Late afternoon and evening
When sleepiness hits	Early evening	Around a typical bedtime	Well after a typical bedtime
Workday midpoint vs. free-day midpoint	Nearly the same	Somewhat earlier on workdays	Much earlier on workdays

That last row is your rough social jet lag. The bigger the gap, the harder your schedule is fighting your clock.

Social jet lag is the time zone you fly back from every Monday

The phrase “social jet lag” comes from Till Roenneberg, a chronobiologist at the University of Munich (LMU)⁷. It names the clash between your inner clock and the timetable that work, school and friends set for you. By 2012, his team’s online Munich ChronoType Questionnaire had drawn more than 130,000 responses⁷. Based on that data, Roenneberg estimated that roughly two in three people in Western countries carry a significant clash⁷.

Picture an evening type who sleeps from 1 to 9 on weekend mornings but from 11 at night until 6:30 on workdays. Every Monday, that body is asked to jump about two hours, like flying across two time zones without leaving home.

In a 2012 study of about 65,000 Europeans in the journal Current Biology, more social jet lag went along with a higher body mass index, a measure of weight for height⁷⁸. The link held beyond how long people slept⁸.

That’s a survey finding, not proof. Dr. Elliott Lee, a sleep specialist at the Royal Ottawa Health Care Group, told CBC News that causation isn’t clear⁸. People with big gaps may also differ in jobs, stress or diet.

Shift workers face the hardest version. According to NIGMS, night shifts, crossing time zones and late-night screen light can all scramble the body’s timing². Keep that up for years, with too little sleep, and the agency lists obesity, diabetes, mood disorders, heart and blood pressure problems, and cancer among the possible costs².

In 2019, the World Health Organization’s cancer agency, IARC, classified night shift work as “probably carcinogenic to humans,” based on limited evidence in people and stronger evidence from animal and lab studies¹². Our article on irregular schedules explains what that label means.

The daylight saving fight is really about morning light

Nearly everyone agrees on one thing: stop switching. In a 2020 AASM survey of about 2,000 U.S. adults, two-thirds supported ending the seasonal time change and 11% opposed it¹⁰. The fight is over which time to keep.

The AASM’s 2020 position statement in the Journal of Clinical Sleep Medicine says the switching should end in favor of permanent, year-round standard time⁹. By September 2020, 19 organizations had endorsed it¹⁰. Lead author Dr. M. Adeel Rishi of Mayo Clinic in Eau Claire, Wisconsin, called standard time the closest match to the body’s sleep-wake cycle¹⁰.

The reasoning comes from the clock. Daylight time means darker mornings and lighter evenings¹⁰. Morning light helps anchor the clock, while bright evening light can disrupt melatonin‘s rise⁴.

The statement also links the spring switch to daylight time with more heart problems, mood disorders and car crashes⁹. It is candid on one point: the effects of staying on daylight time all year haven’t been well studied⁹.

The U.S. has tried permanent daylight time before. In the 1970s, Congress enacted it, then repealed it less than a year later, according to the AASM¹¹. In March 2022, the Senate passed an earlier version of the Sunshine Protection Act¹¹. The clocks kept changing anyway.

The 2026 House bill would make daylight time permanent¹. A state already on year-round standard time when the law kicked in could stay put, but no state could switch to standard time afterward¹. The AASM backs a different bill, the Sunshine for Our Kids Act, which would set permanent standard time and let states opt into daylight time¹.

The academy warns of more crashes and pedestrian deaths under permanent daylight time, especially among children waiting for buses or walking to school in the dark¹. As of the academy’s July 15, 2026, statement, the bill was waiting on the Senate, which had not voted on it¹. We could not confirm any later action, so check congress.gov for the latest.

How strong is the evidence?

Claim	Evidence level	What it rests on
A gene-based master clock, set mainly by light, times sleep and hormones	Strong evidence	Nobel Prize work and NIH summaries234
Chronotype is partly inherited	Strong evidence	A 697,828-person genetic study; each gene’s effect is small6
Being a morning type improves mental health	Promising but early	One Mendelian randomization analysis6
Social jet lag causes weight gain	Promising but early	Large surveys show a link; they can’t show cause78
The spring clock change raises short-term risks	Promising but early	Studies of heart events, mood and crashes cited by the AASM9
Permanent standard time is healthier than permanent daylight time	Not enough evidence	No long-term studies of year-round daylight time; the case rests on clock biology9
Night shift work causes cancer	Promising but early	IARC found limited evidence in people and sufficient evidence in animals; the label names a hazard, not a level of risk12

A week of working with your clock

Start this plan after you’ve tracked your chronotype. Each step builds on the one before.

Day	Focus	What to do
1	Pick an anchor	Choose a wake time you can keep every day, weekends included.
2	Get light early	Go outside soon after waking, even on a cloudy day.
3	Dim the evening	Lower bright lights and screens before bed, since bright late-evening light can disrupt melatonin’s rise4.
4	Match tasks to your peak	Put your hardest thinking in your sharpest hours.
5	Steady your meals	Eat at roughly the same times; food is a time cue for your body’s clocks2.
6	Guard the weekend	Keep your free-day wake time close to your workday time.
7	Recheck the gap	Compare your midpoints again. A smaller gap means less social jet lag.

Night owls may never become larks, and that’s fine. The goal is a clock that’s steady and in step with your life, not a 5 a.m. alarm.

Living by the sun is an old idea, and science backs much of it

For most of human history, people lived by sunrise and sunset. The science of circadian rhythms suggests the body still expects that, and its main timekeepers are free: daylight in the morning and darkness at night²⁴.

That fits values many natural-health readers hold. Working with your body’s rhythms takes steady habits, time outdoors and regular meals, not a product. Be as skeptical of a gadget that promises to “reset” your clock as you would be of a new drug.

It also asks for respect for differences. Chronotypes are partly inherited⁶. A night owl isn’t lazy, and an early riser isn’t morally better. Schools, workplaces and clock laws that fit more people’s biology are a fair thing to ask for.

When your clock, or your sleep, needs a professional

Being a night owl isn’t a disorder. Doctors do treat circadian rhythm sleep-wake disorders, in which the clock’s timing keeps you from falling asleep or waking at the times you need¹⁴. If you can’t fall asleep until very late and can’t wake for work or school despite steady habits, see a sleep clinician.

Talk with a clinician if you notice any of these:

• A bed partner hears loud snoring, gasping, choking or pauses in your breathing¹³.
• You feel very sleepy in the daytime or need stimulants to stay awake¹³.
• You have trouble falling or staying asleep at least three nights a week for three months or more¹⁵.
• You get creeping or tingling feelings in your legs in the evening that ease when you move¹³.
• You act out your dreams, sleepwalk or often can’t move when you first wake¹³.

If you yawn constantly, struggle to keep your eyes open or can’t recall the last few miles while driving, pull over somewhere safe¹³. If poor sleep comes with hopeless thoughts or thoughts of harming yourself, call or text the 988 Suicide & Crisis Lifeline. Later articles in this series cover insomnia, sleep apnea, restless legs and shift work disorder.

Questions readers ask

The bottom line

Your body runs on a clock built from genes, kept on time by light and tuned by meals and habits. Some people are wired to run a little early or a little late, and teens and older adults shift in opposite directions. When your schedule fights your clock every week, you feel it as social jet lag.

You can’t change your genes, but you can give your clock steady signals: a fixed wake time, morning daylight, dim evenings and regular meals. The fight in Congress asks the same question on a national scale: should our clocks follow the sun or fight it?

Keep exploring: morning light exposure.

Related reading

• A cloudy morning outside beats a bright office for your body clock
• Sleep pressure builds all day, and your body clock decides when it wins
• One in seven workers clocks in during off-hours, and sleep is the first thing to anchor
• Intermittent fasting ties ordinary dieting in trials, which can be good news
• Travel wellness starts with the basics, not a suitcase of supplements

Sources

1. American Academy of Sleep Medicine. “AASM Condemns House Passage of Sunshine Protection Act.” AASM, July 15, 2026. aasm.org
2. National Institute of General Medical Sciences. “Circadian Rhythms” (fact sheet). NIH, content reviewed September 2023, updated May 20, 2025. nigms.nih.gov
3. WGBH News / NPR. “Nobel Prize in Medicine Is Awarded to 3 Americans for Work on Circadian Rhythm.” October 2, 2017. wgbh.org
4. National Heart, Lung, and Blood Institute. “Sleep-Wake Cycle” (How Sleep Works). NIH, updated March 24, 2022. nhlbi.nih.gov
5. Brown TM, Brainard GC, Cajochen C, et al. “Recommendations for Daytime, Evening, and Nighttime Indoor Light Exposure to Best Support Physiology, Sleep, and Wakefulness in Healthy Adults.” PLoS Biology, 2022;20(3):e3001571 (Thomas Jefferson University repository record). jdc.jefferson.edu
6. Jones SE, Lane JM, Wood AR, et al. “Genome-Wide Association Analyses of Chronotype in 697,828 Individuals Provides Insights Into Circadian Rhythms.” Nature Communications, 2019;10:343 (University of Bristol research record). research-information.bris.ac.uk
7. Ludwig-Maximilians-Universität München, via ScienceDaily. News release on Roenneberg T, Allebrandt KV, Merrow M, Vetter C, “Social Jetlag and Obesity,” Current Biology, 2012. May 2012. sciencedaily.com
8. CBC News. “Sleep Loss From ‘Social Jet Lag’ Tied to Obesity” (report on Roenneberg et al., Current Biology, 2012). CBC. cbc.ca
9. Rishi MA, Ahmed O, Barrantes Perez JH, et al. “Daylight Saving Time: An American Academy of Sleep Medicine Position Statement.” Journal of Clinical Sleep Medicine, 2020;16(10):1781–1784 (AASM abstract page). pubmed.ncbi.nlm.nih.gov
10. MDedge. “Experts Advocate Elimination of Daylight Saving Time.” September 8, 2020. mdedge.com
11. American Academy of Sleep Medicine. “American Academy of Sleep Medicine Opposes Permanent Daylight Saving Time Bill.” AASM, May 23, 2022. aasm.org
12. International Agency for Research on Cancer. “IARC Monographs Volume 124: Night Shift Work. Questions and Answers.” IARC, July 5, 2019. iarc.who.int
13. National Heart, Lung, and Blood Institute. “Your Guide to Healthy Sleep.” NIH Publication No. 11-5271, revised August 2011. nhlbi.nih.gov
14. MedlinePlus. “Sleep Disorders.” National Library of Medicine, updated December 4, 2025. medlineplus.gov
15. American Academy of Sleep Medicine. “Insomnia” (provider fact sheet). AASM. aasm.org