The U.S. House of Representatives has voted to approve the Sunshine Protection Act, a bill that would establish permanent daylight saving time (DST) nationwide. The legislation now proceeds to the Senate for consideration. If passed by the Senate and signed into law by President Donald Trump, who supports the measure, the twice-yearly clock changes would cease.
However, many medical professionals and sleep experts express reservations about making DST permanent, arguing that standard time (ST) aligns more closely with human circadian biology and offers greater health and safety benefits. The American Academy of Sleep Medicine supports permanent standard time, stating it is best for human health and safety while highlighting the potential harms of seasonal time changes.
Dr. Joanna Fong-Isariyawongse, an associate professor of neurology at the University of Pittsburgh, explained that the body's internal clock is primarily set by morning sunlight. "The closer we keep the clock to the actual sun, the less friction your body fights every single day," she stated, emphasizing that aligning noon with the sun's position overhead is most conducive to health.
Dr. Randy Nelson, a professor at West Virginia University School of Medicine, noted a divergence between public and business interests and the views of medical and science experts. While the public and business sectors often favor permanent DST for its additional evening daylight, sleep medicine organizations generally recommend permanent ST for its alignment with human biology.
"The broadest area of agreement is that ending the twice-yearly clock changes would be beneficial," Nelson said. "The main debate is which permanent time — standard time or daylight saving time — would produce the better overall balance of health, safety and convenience."
Permanent DST offers benefits such as later sunsets, providing more daylight for after-work activities and exercise, and potentially reducing vehicle crashes and pedestrian fatalities during evening commutes. Conversely, it would result in darker winter mornings. In cities like Chicago, sunrise could occur around 8:20 a.m., and in parts of the northern U.S., it could be after 9:00 a.m., coinciding with school and work hours.
Permanent standard time would lead to earlier winter sunsets but would preserve morning light, which experts believe is crucial for regulating sleep and mental health. Fong-Isariyawongse pointed to research suggesting permanent ST is associated with a lower risk of stroke and obesity compared to permanent DST. "Our body really needs that morning light to know it’s time to wake up," she said, warning that losing it for months can lead to disrupted sleep, difficulty waking, and potentially increased anxiety and depression.
Adolescents may be particularly affected by permanent DST due to their biological chronotypes, which naturally involve later sleep and wake times. Fong-Isariyawongse expressed concern that darker winter mornings would exacerbate existing sleep deficits in teenagers, sending them to school and crossing streets in the dark when their alertness is lowest.
The U.S. previously experimented with permanent DST during the 1973-1974 energy crisis. The initiative, initially popular, saw its support wane as the public experienced prolonged dark winter mornings, particularly regarding children's safety traveling to school. Congress repealed the measure after less than a year.
Despite expert consensus favoring standard time, permanent DST has historically received support from industries like golf and travel, which benefit from extended daylight hours for recreation. Officials in Southern and coastal states also tend to favor the change. However, sleep doctors and major sleep organizations maintain that permanent standard time remains the healthier and more biologically aligned option.