A recently published Penn Medicine study revealed the impacts that daylight savings time can have on physical and mental health.
This weekend, Americans will turn their clocks back one hour to mark the end of daylight savings time. What may feel like a minor schedule change can affect sleep, mood, concentration, and even physical health, according to Indira Gurubhagavatula, director of the Sleep Medicine Fellowship at Penn’s Perelman School of Medicine.
In an interview with Penn Today, Gurubhagavatula said the twice-yearly system unsettles the body’s natural rhythm.
She added that the brain’s internal “master clock” coordinates dozens of daily cycles including sleep, body temperature, hormone levels, and digestion. When social time and solar time fall out of sync, Gurubhagavatula said people are not actually “saving daylight” but rather “just redistributing it.”
This can leave people feeling fatigued or unfocused, the study said.
Her research and clinical works focus on circadian rhythms, the roughly 24-hour cycle that guide processes like sleep, digestion, and hormone regulation. As defined by Stanford University’s Sleep Corner, “the phrase ‘circadian rhythm’ is used to describe any operation in your body that runs on a 24-hour cycle; for example, your digestive system is coordinated through a circadian rhythm that minimizes activity in the evening to help you sleep through the night.”
Gurubhagavatula told Penn Today that the brain’s master clock keeps these rhythms in sync even small shifts can throw the balance off.
“We function best when all of these clocks are aligned,” she stated. “The time change is stressful on the cardiovascular system. People may also feel a general sense of being unwell and may experience physical exhaustion.”
Separately, the American Medical Association recommends adopting permanent standard time, stating that “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.”
Although nationwide policy change remains uncertain, Gurubhagavatula explained that simple habits, like getting morning light, limiting caffeine later in the day, and gradually shifting bedtime by 10-15 minutes can help.
“Standard time is ‘natural time,’” she said. “It aligns best with how our bodies are built to function.”
