From medical professionals to journalists and engineers, employees in several fields burn the midnight oil, forced to function on irregular sleep cycles. This often adversely affects people’s physical and mental well-being and experiencing symptoms like insomnia or excessive daytime sleepiness can also point to shift work disorder, a circadian rhythm sleep disorder.
Inadequate sleep as a result of night shifts can also lead to mental health challenges like fatigue, irritability, mood disturbance, and be a risk factor for illnesses such as cardiovascular disease and cancer. Latest research by Washington State University Health Sciences Spokane has revealed insights as to why non-traditional work hours increase the risk for cancer. It indicated that night shifts disrupt the natural 24-hour rhythms in the activity of certain cancer-related genes, making night shift workers more vulnerable to the disease.
In a partnership between the WSU Sleep and Performance Research Center and the U.S. Department of Energy’s Pacific Northwest National Laboratory (PNNL), scientists aimed to study the potential involvement of the biological clock, the built-in mechanism that enables bodies to maintain a 24-hour night and day cycle. Each cell also has its own built-in clock involving genes known as clock genes that are rhythmic, meaning their activity levels vary depending on the time of day.
Researchers worked around the hypothesis that the expression of genes associated with cancer might be rhythmic too and that night shift work may disrupt the rhythmicity of these genes.
The experiment was conducted with 14 participants, half of them completed a three-day simulated night shift schedule, while the other half were on a similar day shift schedule.
DNA repair that showed distinct rhythms in the day shift condition lost their rhythmicity in the night shift condition.
Analyses of white blood cells taken from the participants showed that the rhythms of many of the cancer-related genes varied in the night shift condition compared to the day shift condition. It was also observed that genes related to DNA repair that showed distinct rhythms in the day shift condition lost their rhythmicity in the night shift condition.
Investigating the outcomes of these changes, they found that white blood cells of night shift participants showed more evidence of DNA damage than those who took part in the day shift. Further study revealed increased DNA damage in the night shift condition indicating that they were more vulnerable to external damage from radiation, a known risk factor for DNA damage and cancer.
“Taken together, these findings suggest that night shift schedules throw off the timing of expression of cancer-related genes in a way that reduces the effectiveness of the body’s DNA repair processes when they are most needed,” said co-corresponding author Jason McDermott, a computational scientist, PNNL.
The researchers will be exploring further by conducting the same experiment on real-world shift workers who have consistently been on day or night shifts for several years to determine whether the unrepaired DNA damage builds up over time, thereby increasing the risk of cancer.
“Night shift workers face considerable health disparities,” said co-senior author Hans Van Dongen, professor, WSU Elson S. Floyd College of Medicine and director, WSU Sleep and Performance Research Center. “It is high time that we find diagnosis and treatment solutions for this underserved group of essential workers so that the medical community can address their unique health challenges.”