Daylight Saving Time may have dark impact on the body – without saving time


Rutgers University’s Helmut Zarbl, an expert in circadian rhythm and its influence on sleep-wake cycles, hormone release, eating habits and more, provides insight on how daylight saving time disrupts our biological clocks and affects our health – and fails to yield an extra hour of sleep, as so often claimed.

Daylight saving time was introduced in Europe and the United States after World War I as part of an effort to conserve energy and decrease the use of fuel for lighting and heating. This Sunday morning, most people in the United States will turn their clocks back by one hour in observance of daylight saving time.

Circadian rhythm regulates many important biological processes, such as hormone production and sleep patterns, and is largely controlled by external cues in the environment – mainly light, said Dr. Zarbl, the director of Rutgers Environmental and Occupational Health Sciences Institute and chair of the Environmental and Occupational Health Department at Rutgers School of Public Health.

“Changing sleep-wake cycles by an hour has an effect on our circadian clock,” he said. “Since light is normally a key regulator of our biological clock, the change will shift the phase of our rhythm away from that of the central pacemaker. As with any phase change, this will cause disturbances in sleep, metabolism, mood, bodily functions and productivity.”

Dr. Zarbl said daylight saving time-associated changes result in higher rates of car and workplace accidents, and a few studies suggest a slight increase in heart attacks and stroke, probably in those already at a higher risk. He also clarified the common misconception that people get an extra hour of sleep, saying they are actually just changing the phase. “As with any change in sleep cycles due to shift work, jet lag, etc., it takes about a week to reset your biological clock,” he said.

To best adapt to this change Dr. Zarbl said, “Do not fight the change or keep referring to the previous time schedule. The sooner you adapt, the sooner you will feel normal again, so adjust your eating and sleep schedules accordingly. Don’t wait until Monday to make the necessary changes. And avoid using caffeine and other stimulants or drugs to help adjust.”

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