New research reveals that living against our internal clocks can harm long-term health by altering gut and brain interactions. –ScienceDaily
While most Americans relax for bed, 15 million people just get to work. These hospital workers, emergency responders, factory operators and others are among the 20% of the world’s population who work shifts. Their different sleep-wake cycle increases their risk of many health conditions, including diabetes, heart attacks, cancer, and strokes.
Now, new research published in Neurobiology of sleep and circadian rhythms shows that the harmful effects of shift work can be long-lasting, even after a return to a normal schedule.
“Shift work, particularly rotating shift work, disrupts our biological clocks and this has important ramifications in terms of health and well-being and its link to human disease,” said David Earnest, professor in the Department of Neuroscience. and experimental therapeutics in Texas. A&M University College of Medicine. “When our internal body clocks are in sync correctly, they coordinate all of our biological processes to occur at the right time of day or night. When our body clocks are out of alignment, whether because of shift work or other disturbances, this leads to physiological changes, biochemical processes and various behaviors.
A previous study by Earnest and colleagues found that animal models subjected to rotating shift work schedules had more severe stroke outcomes, in terms of brain damage and functional deficits, than those subjected to regular cycles of shift work. 24 hours day and night. Men were distinguished by poorer outcomes in which mortality rates were much higher.
This new study took a different approach. Rather than looking at the immediate effects of shift work on strokes, the researchers returned all subjects to regular 24-hour cycles and waited until their mid-life equivalent – when humans are most likely to have a stroke – to assess the severity and outcome of the stroke.
“What has already emerged from epidemiological studies is that most people only experience shift work for five to eight years and then presumably revert to normal working hours,” Earnest said. “We wanted to determine if this was enough to erase all the problems of these circadian rhythm disturbances, or do these effects continue even after returning to normal working hours?”
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 kept on a regular day-night cycle throughout the study, they exhibited persistent alterations in their sleep-wake rhythms, with periods of abnormal activity when sleep would normally have occurred. When they suffered strokes, 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 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 gut inflammatory mediators in subjects exposed to a shift work schedule. “We now think that part of the mechanism underlying what we see in terms of circadian rhythm disruption causing more severe strokes may involve altered brain-gut interactions,” Earnest said.
The results of this study could eventually lead to the development of interventions that block the adverse effects of disrupted circadian rhythms. In the meantime, shift workers can improve the care of their internal clocks by trying to maintain 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 could extend to many other people who work very different schedules from day to day.
“Because of the computer age, many more of us no longer work 9 a.m. to 5 p.m. We take our jobs home and sometimes work late at night,” Earnest said. “Even those of us who work regular hours tend to stay up late on weekends, producing what is known as ‘social jet lag’, which also throws our biological clocks out of whack so that they no longer keep the exact time.All of this can have the same effects on human health as shift work.
To avoid some of these health risks, the best approach is to maintain a regular schedule of waking, sleeping, and eating times that doesn’t vary dramatically from day to day. Also, avoid common cardiovascular risk behaviors like eating a high-fat diet, not getting enough physical activity, drinking too much alcohol, and smoking.