Falling back and springing ahead may have consequences for human health.
When the clock “falls back” to standard time (ST) early Sunday, that should be the last seasonal time change for the United States, say physician experts on sleep.
Daylight saving time (DST) will end at 2 a.m. Nov. 5, when clock time falls back one hour for the winter. This week, the American Academy of Sleep Medicine (AASM) reaffirmed its position that DST desynchronizes day, night, and people’s internal clocks, creating potential health risks.
“It is the position of the AASM that the United States should eliminate seasonal time changes in favor of permanent standard time (ST), which aligns best with human circadian biology,” AASM said. “Permanent standard time is the optimal choice for health and safety: an American Academy of Sleep Medicine position statement” was published in the Journal of Clinical Sleep Medicine.
AASM said three clocks affect human activities. The Society for Research on Biological Rhythms also explained the time measures in “Why Should We Abolish Daylight Saving Time?” in the Journal of Biological Rhythms.
The internal biological rhythm is the circadian clock. Earth revolving and orbiting the sun creates the solar clock. The social clock dictates times for activities such as school and work.
When the three clocks don’t match up, bad things can happen.
“Springing ahead,” moving clocks ahead by an hour in the spring, causes people to lose sleep. That can lead to health issues ranging from higher heart rates and blood pressure, to atrial fibrillation, to increased risk of pregnancy loss following in-vitro fertilization, to more car crashes, according to AASM, which cited a number of studies on various health conditions and effects.
Likewise, “falling back” in November also causes sleep disruption that can lead to adverse health effects, even though it is “commonly thought to be beneficial because it is associated with ‘an extra hour of sleep,’” AASM said.
“Evidence indicates that the body clock does not adjust to DST even after several months, so that ongoing sleep debt and circadian misalignment continue to persist,” AASM said.
This week’s position paper reiterated arguments from a 2020 AASM position paper that acknowledged “there is little direct evidence regarding the chronic effects of DST.” There may be some benefits, such as decreases in crime rates and motor vehicle crashes due to more daylight in the evenings.
Seasonal time changes have prompted debate for decades.
AASM noted in 1973, Congress established permanent DST due to the oil embargo of the Organization of the Petroleum Exporting Countries. The assumption was “that more evening light would lead to energy savings,” but actual energy savings were minimal. Permanent DST was “highly unpopular,” likely because people had more days of dark mornings, and Congress repealed it a year later.
Last year, the Senate approved a bill proposing year-round DST, but the House of Representatives did not act on it.
States may exempt themselves from DST, and Hawaii, Arizona, and U.S. territories do so. AASM cited the Congressional Research Service, which found various states had proposals to eliminate time changes – but they were split on using DST or ST. As of March this year, the National Conference of State Legislatures reported 19 states had enacted year-round daylight saving time.
Mexico eliminated DST last year, and in 2021 the European Parliament voted to eliminate mandatory DST.