Decreased DNA Repair Links Shift Work and Increased Cancer Risk Interview with:
Parveen Bhatti, PhD
Associate Member
Fred Hutchinson Cancer Research Center What is the background for this study? What are the main findings?

Response: Evidence in humans for an association between shift work and cancer has been mixed. This may be due to difficulties in accurately assessing long-term exposures to shift work in studies of cancer risk. We took a different approach that circumvented these difficulties. Rather than look at cancer risk directly, we measured, among actively employed shift workers, a marker of DNA damage that has been linked to cancer.

When repaired by cellular machinery, this particular marker is excreted in urine where it can be measured. We found that, compared to sleeping at night during their night off, shift workers had lower urinary levels of the DNA damage marker during their night work. This effect appears to be driven by reductions in circulating melatonin levels among shift workers during night work relative to night sleep. Given that melatonin has been shown to enhance repair of DNA damage, our results suggest that, during night work, shift workers have reduced ability to repair DNA damage resulting in lower levels being excreted in their urine. Because of this, shift workers likely have higher levels of DNA damage remaining in their cells, which can lead to mutations and cause cancer. What should clinicians and patients take away from your report?

Response: Our study provides additional evidence to support a link between shift work and cancer and has uncovered a potential pathway by which shift work contributes to increased risks of cancer. What recommendations do you have for future research as a result of this study?

Response: Because the decreased ability to repair DNA damage seems to be linked to reduced melatonin levels, our results suggest that melatonin supplementation may be a way for shift workers to reduce their risk of cancer. We are currently pursuing funding for a trial to evaluate the ability of melatonin supplements to improve DNA repair among shift workers. Is there anything else you would like to add?

Response: It’s important to await the results of additional research, such as the trial we propose, before shift workers decide to adopt melatonin supplementation as a way to improve their health. Melatonin supplements are not FDA regulated and there may be yet unidentified side effects of melatonin supplementation among shift workers Thank you for your contribution to the community.


Parveen Bhatti, Dana K Mirick, Timothy W Randolph, Jicheng Gong, Diana Taibi Buchanan, Junfeng (Jim) Zhang, Scott Davis. Oxidative DNA damage during night shift work. Occupational and Environmental Medicine, 2017; oemed-2017-104414 DOI: 10.1136/oemed-2017-104414

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