The body’s internal clock, or circadian rhythm, is a 24-hour cycle that regulates various biological processes, such as hormone levels, body temperature, and sleep. The circadian rhythm is synchronized with the external cues of light and darkness, which signal the body when to be awake or asleep.
However, for shift workers, their work hours and sleep hours are misaligned with these natural cues. This can cause significant difficulties with falling and staying asleep, or sleeping when desired. This phenomenon, known as shift work disorder, can impair the quality and quantity of sleep, and affect the mental and physical health of shift workers.
“People who work 9-to-5 shifts are typically awake when the sun is up, which is aligned with their body’s internal circadian clock. But for shift workers, their work hours and sleep hours are misaligned with the natural cues to be awake or asleep,” says Eric Zhou, an assistant professor in the Division of Sleep Medicine at Harvard Medical School.
Shift work disorder can have serious consequences for the health and well-being of shift workers. A 2022 research review in the Journal of Clinical Sleep Medicine links shift work to higher risks for cardiovascular diseases, metabolic disorders, accidents, and certain types of cancer.
“The research is consistent and powerful,” Zhou says. “Working and sleeping during hours misaligned with natural light for extended periods of time is not likely to be healthy for you”.
Some of the specific health effects that have been associated with shift work include:
– Metabolic syndrome: A study published in Advances in Nutrition found that shift workers on rotating schedules eat more erratically and frequently than day workers, snack more at night, and consume fewer healthier foods with potentially more calories. This can increase the risk of obesity, diabetes, high blood pressure, and high cholesterol, which are components of metabolic syndrome.
– Colorectal cancer: A review of multiple studies published in the Journal of Investigative Medicine suggested that disrupting the circadian rhythm through shift work may increase the odds of developing colorectal cancer, a malignancy with strong ties to lifestyle factors.
– Circadian misalignment: Researchers have found that even a few days of being awake at night and asleep during the day caused shifting of the rhythms in certain metabolic pathways without significantly shifting the brain’s master circadian clock. This finding may help explain why night-shift sleep patterns have been linked to certain metabolic disorders, such as obesity and diabetes.
The evidence suggests that shift work, particularly night shifts, can have a significant impact on health and well-being. It’s clear that more research is needed to fully understand the implications and develop strategies to mitigate the risks associated with shift work. In the meantime, shift workers can try to adopt some healthy habits, such as maintaining a regular sleep schedule, avoiding caffeine and alcohol before bedtime, using dark curtains or eye masks to block out light, and seeking professional help if they experience persistent or severe sleep problems.
Relevant articles:
– Shift work can harm sleep and health: What helps?
– Shift Work Sleep Disorder (SWSD) – Cleveland Clinic
– How night shifts disrupt metabolism – National Institutes of Health (NIH)
– Over half of night shift workers suffer from sleep disorders: study