Seasonal time change is now up for consideration in the U.S. Congress, prompting sleep medicine specialists to weigh in on the health impact of a major policy change.
As lawmakers in Washington propose an end to seasonal time changes by permanently establishing daylight saving time (DST), the American Academy of Sleep Medicine (AASM) is pushing for a Congressional hearing so scientists can present evidence in favor of converse legislation – to make standard time the new norm.
According to the AASM, ; however, the switch from standard time to DST incurs more risk.
“Current evidence best supports the adoption of year-round standard time, which aligns best with human circadian biology and provides distinct benefits for public health and safety,” the AASM noted in a 2020 position statement on DST.
The statement cites a number of studies that have reported associations between the switch to DST and acute, negative health outcomes, including higher rates of hospital admission, cardiovascular morbidity, atrial fibrillation, and stroke. The time shift has been associated with a spectrum of cellular, metabolic, and circadian derangements, from increased production of inflammatory markers, to higher blood pressure, and loss of sleep. These biological effects may have far-reaching consequences, including increased rates of fatal motor accidents in the days following the time change, and even increased volatility in the stock market, which may stem from cognitive deficits.
U.S. Senator Marco Rubio (R-Fla.) and others in the U.S. Congress have reintroduced the 2019 Sunshine Protection Act, legislation that would make DST permanent across the country. According to a statement on Sen. Rubio’s website, “The bill reflects the Florida legislature’s 2018 enactment of year-round DST; however, for Florida’s change to apply, a change in the federal statute is required. Fifteen other states – Arkansas, Alabama, California, Delaware, Georgia, Idaho, Louisiana, Maine, Ohio, Oregon, South Carolina, Tennessee, Utah, Washington, and Wyoming – have passed similar laws, resolutions, or voter initiatives, and dozens more are looking. The legislation, if enacted, would apply to those states [that] currently participate in DST, which most states observe for eight months out of the year.”
A stitch in time
“The sudden change in clock time disrupts sleep/wake patterns, decreasing total sleep time and sleep quality, leading to decrements in daytime cognition,” said Kannan Ramar, MBBS, MD, president of the AASM and a sleep medicine specialist at Mayo Clinic, Rochester, Minn.
Dr. Kannan Ramar
Emphasizing this point, Dr. Ramar noted a recent study that reported an 18% increase in “patient safety-related incidents associated with human error” among health care workers within a week of the spring time change.
“Irregular bedtimes and wake times disrupt the timing of our circadian rhythms, which can lead to symptoms of insomnia or long-term, excessive daytime sleepiness. Lack of sleep can lead to numerous adverse effects on our minds, including decreased cognitive function, trouble concentrating, and general moodiness,” Dr. Ramar said.
He noted that these impacts may be more significant among certain individuals.
“The daylight saving time changes can be especially problematic for any populations that already experience chronic insufficient sleep or other sleep difficulties,” Dr. Ramar said. “Populations at greatest risk include teenagers, who tend to experience chronic sleep restriction during the school week, and night shift workers, who often struggle to sleep well during daytime hours.”
While fewer studies have evaluated the long-term effects of seasonal time changes, the AASM position statement cited evidence that “the body clock does not adjust to daylight saving time after several months,” possibly because “daylight saving time is less well-aligned with intrinsic human circadian physiology, and it disrupts the natural seasonal adjustment of the human clock due to the effect of late-evening light on the circadian rhythm.”
According to the AASM, permanent DST, as proposed by Sen. Rubio and colleagues, could “result in permanent phase delay, a condition that can also lead to a perpetual discrepancy between the innate biological clock and the extrinsic environmental clock, as well as chronic sleep loss due to early morning social demands that truncate the opportunity to sleep.” This mismatch between sleep/wake cycles and social demands, known as “social jet lag,” has been associated with chronic health risks, including metabolic syndrome, obesity, depression, and cardiovascular disease.