In a new study, researchers found new clues why night shift workers are at increased risk of developing certain types of cancer.
They tested healthy volunteers who were on simulated night shift or day shift schedules.
Findings suggest that night shifts disrupt natural 24-hour rhythms in the activity of certain cancer-related genes, making night shift workers more vulnerable to damage to their DNA while at the same time causing the body’s DNA repair mechanisms to be mistimed to deal with that damage.
Though more research still needs to be done, these discoveries could someday be used to help prevent and treat cancer in night shift workers.
The research was conducted by a team at Washington State University.
There has been mounting evidence that cancer is more prevalent in night shift workers, which led the World Health Organization’s International Agency for Research on Cancer to classify night shift work as a probable carcinogenic.
However, it has been unclear why night shift work elevates cancer risk, which our study sought to address.
In the study, the team focused on the potential involvement of the biological clock, the body’s built-in mechanism that keeps us on a 24-hour night and day cycle.
Though there is a central biological clock in the brain, nearly every cell in the body also has its own built-in clock.
This cellular clock involves genes known as clock genes that are rhythmic in their expression, meaning their activity levels vary with the time of day or night.
The researchers hypothesized that the expression of genes associated with cancer might be rhythmic, too, and that night shift work might disrupt the rhythmicity of these genes.
To test this, they conducted a simulated shift work experiment that had 14 participants spend seven days inside the sleep laboratory.
Half of them completed a three-day simulated night shift schedule, while the other half were on a three-day simulated day shift schedule.
Analyses of white blood cells taken from the blood samples showed that the rhythms of many of the cancer-related genes were different in the night shift condition compared to the day shift condition.
Notably, genes related to DNA repair that showed distinct rhythms in the day shift condition lost their rhythmicity in the night shift condition.
The researchers then found that white blood cells in night shift participants showed more evidence of DNA damage than those of day shift participants.
What’s more, cells that were radiated in the evening showed increased DNA damage in the night shift condition as compared to the day shift condition.
This meant that white blood cells from night shift participants 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.
One author of the study is Shobhan Gaddameedhi.
The study is published in the Journal of Pineal Research.
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