According to a new study, living against our biological body clocks could harm our long-term health by changing gut and brain interactions.
While most Americans are getting ready for bed, 15 million people are just getting started. These healthcare workers, emergency personnel, industrial operators and others are among the 20 percent of the world’s shift-working population. Your irregular sleep-wake cycle increases your risk of several health problems, including diabetes, heart attacks, cancer, and strokes.
However, shift work could have worse consequences than previously thought. According to a recent study published in the journal Neurobiology of sleep and circadian rhythmsthe negative consequences of shift work can last a long time, even after returning to a regular schedule.
“Shift work, especially rotating shift work, confuses our body clocks and this has important ramifications for our health and well-being and connection to human disease,” said David Earnest, a professor in the Department of Neuroscience. and Experimental Therapeutics of Texas. A&M College of University Medicine. “When our internal body clocks are properly synchronized, they coordinate all of our biological processes to occur at the correct time of day or night. When our body clocks are misaligned, either by shifts or other disruptions, this predicts changes in physiology, biochemical processes, and various behaviors.”
Earnest and colleagues found that animal models with rotating shift work schedules had worse stroke outcomes in terms of both brain damage and functional impairment than those with typical 24-hour day-night cycles. Men fared much worse, with substantially higher death rates.
This groundbreaking research took a new approach. Instead of looking at the immediate impact of shift work on strokes, the researchers returned all individuals to typical 24-hour cycles and waited until their equivalent in middle age, when people are more likely to have a stroke, to assess stroke severity and outcomes.
“What’s already borne out in epidemiological studies is that most people only experience shift work for five to eight years and then presumably return to normal work schedules,” Earnest said. “We wanted to determine if that’s enough to erase the problems these circadian rhythm disruptions have, or do these effects persist even after returning to normal work schedules?”
They found that the health impacts of shift work do, in fact, persist over time. The sleep-wake cycles of subjects with shift work schedules never returned to normal, even after post-exposure to a regular schedule. Compared to controls maintained on a regular day-night cycle throughout the study, they showed persistent disruptions in their sleep-wake rhythms, with periods of abnormal activity when sleep would normally have occurred. When they had stroke, their outcomes were again much worse than the control group, except that women had more severe functional deficits and higher mortality than men.
“The data from this study have additional health-related significance, especially in women, because stroke is a risk factor for dementia and disproportionately affects older women,” said Farida Sohrabji, professor in the Department of Neuroscience and Experimental Therapeutics and director of the Women’s Health in Neuroscience Program.
The researchers also observed increased levels of gut inflammatory mediators in subjects exposed to a shift work schedule. “We now think that part of the underlying mechanism of what we’re seeing in terms of circadian rhythm disruption causing more severe strokes may involve altered interactions between the brain and the gut,” Earnest said.
The results of this study could eventually lead to the development of interventions that block the adverse effects of altered circadian rhythms. Meanwhile, shift workers can improve the care of their internal body clock by trying to maintain a regular schedule as much as possible and avoiding a high-fat diet, which can cause inflammation and also disrupt the timing of circadian rhythms.
This research has clear implications for shift workers, but could be extended to many other people who maintain schedules that differ greatly from day to day.
“Because of the computer age, many more of us are no longer working nine to five. We’re taking work home and sometimes working late at night,” Earnest said. “Even those of us who work regular hours have a tendency to stay up late on the weekends, producing what’s known as ‘social jet lag,’ which similarly throws off our body clocks because we already they don’t have the exact time. All of this can cause the same effects on human health as shift work.”
To avoid some of these health hazards, Earnest says the best approach is to keep a regular schedule of wake time, sleep time and meal times that don’t vary drastically from day to day. Also, avoid common cardiovascular risk behaviors such as eating a high-fat diet, not getting enough physical activity, drinking too much alcohol, and smoking.
Reference: “Sex Differences in the Dietary Effects of Shift Work Schedules on Circulating Cytokine Levels and Pathological Outcomes of Ischemic Stroke in Midlife” by David J. Earnest, Shaina Burns, Sivani Pandey, Kathiresh Kumar Mani and Farida Sohrabji, 30 June 2022, Neurobiology of sleep and circadian rhythms.
The study was funded by the National Institutes of Health.
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