According to new research, living against our body’s biological clock may harm our long-term health by altering the way our gut and brain interact.
While most Americans are getting ready for bed, 15 million people are just getting started. That’s among the 20 percent of the world’s population who work shifts, including health care workers, emergency workers, industrial operators and others. Disruption of their sleep-wake cycle increases the risk of various health problems, including diabetes, heart attack, cancer and stroke.
However, shift work can have worse consequences than we think. According to a recent study published in the journal Neurobiology of sleep and circadian rhythmsthe negative effects of shift work can last long after returning to a regular schedule.
“Shift work, especially back-to-back shift work, disrupts our body clocks and has implications for our health, well-being, and human disease,” said David Earnest, a 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 misaligned, due to shift work or other disturbances, this causes changes in physiology, biochemical processes, and various behaviors.
Ernst and colleagues found that animal models with rotating shift work schedules had worse outcomes in terms of brain damage and functional impairment than those with a typical 24-hour day-night cycle. Men had worse outcomes, with significantly higher mortality rates.
This innovative study took a new approach. Instead of looking at the immediate effect of shift work on stroke, the researchers shifted all the people to a typical 24-hour cycle and waited until their middle-age equivalents — when people are most likely to have a stroke — to assess stroke severity and outcomes.
“What emerges from epidemiological studies is that most people experience shift work for five to eight years and then return to their regular work schedule,” Earnest said. “We wanted to determine if this is enough to reverse the problems with circadian rhythms, or if these effects persist after returning to normal work routines.”
They found that the health effects of shift work did indeed persist over time. The sleep-wake cycles of subjects on shift work schedules did not truly return to normal, even after being exposed to regular schedules. Compared to controls maintained on a regular day-night cycle during the study, they showed persistent changes in sleep-wake rhythms, with periods of abnormal activity when sleep was normal. When they had another stroke, their outcomes were worse than the control group, but the women had higher functional deficits and higher mortality than the men.
“The data from this study have additional health implications, especially for women, because stroke is a risk factor for dementia and disproportionately affects older women,” said Farida Sohrabji, professor and director of the Department of Neuroscience and Experimental Therapeutics. Women’s Health Program in Neurology.
The researchers also observed increased levels of inflammatory mediators in the gut in subjects exposed to shift work. “We now think that part of the underlying mechanism that we’re seeing in terms of circadian rhythms may involve altered interactions between the brain and the gut,” Earnest said.
The results of this study may ultimately lead to the development of interventions that block the negative effects of disrupted circadian rhythms. At the same time, shift workers try to maintain as regular a schedule as possible, avoiding a high-fat diet that can cause inflammation and also alter the timing of circadian rhythms, improving care of the internal body clock.
This study has obvious implications for shift workers, but it could also be extended to many others who maintain significantly different schedules each day.
“Because of the computer age, most of us no longer work from nine to five. “We take our work home and sometimes work late at night,” said Ernest. “Even those of us with regular work schedules tend to stay up late on the weekends, creating something called ‘social jet lag,’ which throws off our body clocks and makes us lose track of time.” All this can have the same consequences for a person’s health as working on a shift.”
According to Ernest, the best way to avoid some of these health risks is to maintain a regular schedule of wake-up times, bedtimes, and meal times 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: David J. “Sex Differences in Dietary Effects of Shift Work Schedules on Circulating Cytokine Levels and Pathological Outcomes in Midlife Ischemic Stroke” by Ernest, Shaina Burns, Siwani Pandey, Kahiresh Kumar Mani, and Farida Sohrabji, June 30, 2022. Neurobiology of sleep and circadian rhythms.
The study was funded by the National Institutes of Health.