According to a new study, living against our biological body clocks can harm our long-term health by altering gut and brain interactions.
While most Americans are getting ready for bed, 15 million individuals are just getting started. These health care workers, emergency responders, industrial operators and others are among the 20 percent of the world’s population who work shifts. Their irregular sleep-wake cycle increases their risk for a number of health problems, including diabetes, heart attacks, cancer and strokes.
However, shift work may have worse consequences than we previously thought. According to a recent study published in the journal Neurobiology of sleep and circadian rhythmsthe negative consequences of shift work can last for a long time, even after returning to a regular schedule.
“Shift work, especially shift work, messes up our body clocks and that has important consequences in terms of our health and well-being and how it relates to human disease,” said David Earnest, professor in the Texas Department of Neuroscience and Experimental Therapeutics. . A&M University College of 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 out of whack, whether from shift work or other disruptions, it 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 for both brain damage and functional impairment than those with typical 24-hour day-night cycles. Men fared much worse, with significantly higher mortality rates.
This innovative research took a new approach. Instead of looking at the immediate impact of shift work on strokes, the researchers put all individuals back into typical 24-hour cycles and waited until their equivalent in midlife—when people are most likely to have a stroke. stroke – to assess the severity and results of the stroke.
“What has already emerged in epidemiological studies is that most people only experience shift work for five to eight years and then apparently return to normal work schedules,” Earnest said. “We wanted to determine, is this enough to erase any problems that these circadian rhythm disruptions have, or do these effects carry over after returning to normal work hours?”
They found that the health impacts of shift work do, indeed, persist over time. The sleep-wake cycles of subjects on shift work schedules never returned to normal, even after subsequent exposure to a regular schedule. Compared to controls kept to a regular day-night cycle throughout the study, they exhibited persistent changes in their sleep-wake rhythms, with periods of abnormal activity when sleep would normally have occurred. When they had a 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 take on added health significance, especially in women, because 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 the Women’s Health Program in Neuroscience.
The researchers also observed increased levels of inflammatory mediators from the gut in subjects exposed to a shift work schedule. “We now think that part of the underlying mechanism for what we’re seeing about circadian rhythm disruption causing more severe strokes may involve altered interactions between the brain and the gut,” Earnest said.
The results of this study may eventually lead to the development of interventions that block the negative effects of disrupted circadian rhythms. Meanwhile, shift workers can improve care of their internal body clocks by trying to keep a regular schedule as much as possible and avoiding a high-fat diet, which can cause inflammation and also alter the timing of circadian rhythms.
This research has clear implications for shift workers, but it can also be extended to many other people who keep schedules that vary widely from day to day.
“Because of the computer age, many more of us no longer work 9 to 5. We take our work home and sometimes work late at night,” Earnest said. “Even those of us who work regular hours have a tendency to stay up late on weekends, producing what’s known as ‘social jet lag’, which similarly breaks down our body clocks so they no longer keep accurate time. All of this can lead to the same effects on human health as shift work.”
To avoid some of these health risks, Earnest says the best approach is to keep a regular schedule of wake-up times, bedtimes and meals that don’t change drastically from day to day. In addition, 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 Dietary Effects of Shift Work on Circulating Cytokine Levels and Pathologic Outcomes of Ischemic Stroke During 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.