Daylight saving time changes impact people differently, according to new research

A man squints in the morning as he reaches to turn off his alarm.

Twice a year, many Americans prepare for daylight saving time – a period when time springs forward by an hour in March and falls back in November – by adjusting their clocks. A study in Scientific Reports found this change impacts people differently – based on their tendency to be an early riser or to go to bed later.  

As part of the Intern Health Study, 831 medical residents shared their genetic information and wore a fitness tracker to track their sleep patterns. Researchers assessed changes in their sleep schedules the week before, during, and after daylight saving time in March 2019. They found early risers, based on genetic associations, took a few days to adjust to losing an hour of sleep and gaining daylight. But those wired to stay up later were affected by the time change a week later. They showed signs of jet lag, the feeling of being misaligned when traveling across time zones.  

The authors note sleep deprivation has been associated with an increased number of car accidents and heart attacks. For medical residents, this extra sleep loss could also translate to an increased number of medical errors and exaggerate depressive symptoms – especially for those most impacted by the time difference. The study was supported by the NHLBI and the National Institute of Mental Health.