As most people prepare to take their well-deserved slumber after a tiring day, some are just about to start their day to work. In America, about 15 million work a permanent night shift or regularly rotate in and out of night shifts, according to the Bureau of Labor Statistics. This suggests that a huge part of the nation’s workforce is vulnerable to the adverse impacts of working nights, including restlessness, fatigue, poor attention, and increased risk for numerous health disorders, such as diabetes, heart attacks, cancer, and strokes.
Consequently, new research published in Neurobiology of Sleep and Circadian Rhythms suggests that the adverse effects of shift work can be long-lasting, even after returning to a normal schedule. The new research is a follow-up to their 2016 study in which they looked at the performance of rats on simulated fixed and shift schedules, where they found that those in the shift-schedule group had greater ischemic stroke severity than the other group.
For their follow-up study, the researchers put the animals on regular, 24-hour schedules and observed the results when they reached midlife, when humans are most at risk of stroke.
According to one of the researchers, shift work, particularly rotating shift work, confuses our body clocks, which has crucial consequences on a person’s health and well-being and connection to human disease.
All of our biological functions are coordinated so that they take place at the appropriate time of day or night when our internal body clocks are correctly synced. Physiological, metabolic, and behavioral changes result from the misalignment of our body clocks, which can be caused by shift work or other disruptions.
Previous studies focused on this association using genetic mutations in core clock genes or shift work-like paradigms, similar to the new research.
Contrary to the findings of most studies, where it is believed that most people only experience shift work for five to eight years and then presumably go back to normal work schedules, the new study aimed to prove whether returning to a normal work schedule is enough to erase any problems that these circadian rhythm disruptions have, or do they continue manifest even after returning to normal work schedules.
Based on the findings of the study, the researchers were able to confirm that the adverse health impacts of shift work do, indeed, persist over time. Even after being exposed to a regular schedule later, the participants’ sleep-wake cycles never reverted to normal. They showed persistent changes in their sleep-wake rhythms compared to controls who remained on a typical day/night cycle throughout the trial, with periods of unusual activity occurring when sleep should have happened. The results of their strokes were once more significantly worse than those of the control group, except that females experienced more severe functional deficits and higher mortality rates than males.
Since stroke is a risk factor for dementia and affects older women disproportionately, the findings of this study are especially important in terms of health among females. The study participants exposed to work shift schedules also showed elevated levels of gut-produced inflammatory mediators, according to the researchers. This potentially explains the association between circadian rhythm disruption and increased stroke severity due to altered interactions between the brain and gut.
The findings from the study can contribute to developing interventions that can help prevent adverse effects of disrupted circadian rhythms on health. People with shift work schedules can also take the initiative to improve the care of their internal body clocks by trying to maintain a regular schedule and a healthy diet, particularly avoiding high-fat foods, which can cause inflammation and alter circadian rhythms as well.
The implications of the study’s findings are not only limited to shift workers but also to people who have developed inconsistent schedules and tend to stay up late on weekends which can also unwind body clocks, preventing them from keeping accurate time. This can also lead to similar effects on human health as shift work.
Hence, to avoid the health hazards brought by disruptions in circadian rhythms, it would be best to keep a regular awake time, sleep time, and mealtimes schedule that doesn’t vary drastically from day to day. It would also be best to avoid common cardiovascular risk habits such as a high-fat diet, a sedentary lifestyle, drinking too much alcohol, and smoking.
Earnest, D. J., Burns, S., Pandey, S., Mani, K. K., & Sohrabji, F. (2022). Sex differences in the diathetic effects of shift work schedules on circulating cytokine levels and pathological outcomes of ischemic stroke during middle age. Neurobiology of Sleep and Circadian Rhythms, 13, 100079. https://doi.org/10.1016/j.nbscr.2022.100079
