Shift work has long-term negative health consequences

Human Head Anatomy Stroke Illustration

A stroke, also known as a brain attack, occurs when the blood supply to part of the brain is cut off or when a blood artery in the brain bursts.

Living against our biological body clocks may harm our long-term health by altering gut and brain interactions, according to a new study.

While most Americans are getting ready for bed, 15 million people are just getting started. These health workers, first responders, industrial operators and others are among the 20 percent of the world’s population who work shifts. Their irregular sleep-wake cycle increases the risk of a variety of health problems, including diabetes, heart attacks, cancer and stroke.

However, shift work can have worse consequences than we previously thought. According to a recent study published in the journal Neurobiology of sleep and circadian rhythmsThe negative effects of shift work can persist for a long time, even after returning to a regular schedule.

“Shift work, especially shifting shifts, messes up our biological clocks, which has important implications for our health and well-being and its link to human disease,” said David Earnest, professor in the Department of Neuroscience and Experimental Therapeutics at Texas A&M. University College of Medicine. “When our internal body clocks are properly synchronized, they coordinate all of our biological processes so that they happen at the right time of day or night. When our body clocks are misaligned, either through shift work or other disturbances, it causes changes in physiology, biochemical processes and various behaviors.”

Earnest and colleagues found that animal models with varying work schedules had worse stroke outcomes in terms of both brain damage and functional impairment than those with typical 24-hour cycles of day and night. Men had much worse outcomes, with significantly higher death rates.

This innovative research was given a new approach. Rather than looking at the immediate impact of shift work on strokes, the researchers switched all individuals back to typical 24-hour cycles and waited until their midlife equivalent — when people are most likely to have a stroke — to assess the severity and outcomes of stroke. to assess a stroke.

“What epidemiological studies have already shown is that most people only work shifts for five to eight years and then presumably return to normal work schedules,” Earnest said. “We wanted to determine, is that enough to erase any problems these circadian rhythm disturbances have, or do these effects persist after returning to normal work schedules?”

They found that the health effects of shift work do indeed persist over time. The sleep-wake cycles of subjects on shift schedules never really returned to normal, even after subsequent exposure to a regular schedule. Compared to controls who had normal day-night cycles throughout the study, they showed sustained changes in their sleep-wake rhythm, with periods of abnormal activity when sleep would normally have occurred. When they had strokes, their results were again much worse than the control group, except that women had more severe functional deficits and higher mortality than the men.

“The data from this study takes on additional health-related significance, especially in women, as stroke is a risk factor for dementia and disproportionately affects older women,” said Farida Sohrabji, a professor in the Department of Neuroscience and Experimental Therapeutics and director of Women’s Health in the United States. Neuroscience program.

The researchers also observed increased levels of inflammatory mediators from the gut in individuals exposed to shift work. “We now think that part of the underlying mechanism for what we’re seeing in terms of circadian rhythm disruption that causes more severe strokes may involve altered brain-gut interactions,” Earnest said.

The results of this research may eventually lead to the development of interventions that block the adverse effects of disrupted circadian rhythms. Meanwhile, shift workers can improve care for their internal body clocks by following a regular schedule as much as possible and avoiding a diet high in fat, which can cause inflammation and also alter the timing of circadian rhythms.

This research has obvious implications for shift workers, but it could extend to many other people who have schedules that vary widely from day to day.

“Because of the computer age, many of us no longer work from nine to five. We take our work home and sometimes work late at night,” says Earnest. “Even those of us who work regularly tend to stay up late on weekends, which is known as ‘social jet lag,’ which similarly relaxes our body clocks so that they no longer keep the correct time. All of this can lead to the same human health effects as shift work.”

To avoid some of these health risks, Earnest says the best approach is to stick to a regular schedule of wake time, sleep time, and meals that doesn’t vary drastically from day to day. In addition, avoid the common cardiovascular risk behaviors such as eating a high-fat diet, not getting enough exercise, drinking too much alcohol, and smoking.

Reference: “Sex Differences in the Diathetic Effects of Shift Work Schedules on Circulating Cytokine Levels and Pathologic Outcomes of Ischemic Stroke in Middle Age” by David J. Earnest, Shaina Burns, Sivani Pandey, Kathiresh Kumar Mani, and Farida Sohrabji, June 30, 2022, Neurobiology of sleep and circadian rhythms.
DOI: 10.116/j.nbscr.2022.100079

The study was funded by the National Institutes of Health.


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