Abstract Introduction The association between body composition and chronic diseases, including certain cancers, is well established. Abdominal adiposity, measured clinically as waist-to-hip ratio, has a strong predictive value for disease development independent of body mass index (BMI). Circadian disturbance exacerbates adiposity-related risk of disease, disproportionately affecting night-shift workers. Though it is understood that circadian disturbance can lead to increased genotoxicity−and subsequent cancer risk−the influence of body composition is poorly understood. Here, we evaluate associations between waist-to-hip ratio, BMI, and shift-work status to DNA damage in immune cells. Methods Non-rotating workers, 15 day-shift (DS) and 15 night-shift (NS) (aged 30-55; 16 females), participated in a controlled, 24-hour laboratory study immediately following their typical workweek. Waist-to-hip ratio and BMI were recorded prior to the study. The laboratory environment involved continuous behavioral monitoring and sustained wakefulness. Peripheral blood mononuclear cells (PBMCs) were collected every 6 hours via intravenous catheter. An alkaline comet assay (CometChip, Cell Array) was used to quantify DNA damage in 1153−4738 PBMCs per participant using comet scoring software (CometScore, Trevigan), providing the percent tail DNA (i.e. total percentage of damaged DNA compared to undamaged DNA). Results T-tests revealed no significant difference between DS and NS workers’ waist-to-hip ratio (t(23)=−0.18, p=0.86) or BMI (t(28)=−1.06, p=0.30). Pearson’s correlations showed that waist-to-hip ratio was strongly associated with DNA damage in NS workers (r=0.79, p 0.001), but BMI was not (r=0.42, p=0.12). In DS workers, there was no significant correlation between DNA damage and waist-to-hip ratio (r=0.45, p=0.19) or BMI (r=−0.15, p=0.58). Conclusion Our findings are consistent with data showing a relationship between increased waist-to-hip ratio and DNA damage/reduced repair mechanisms in PBMCs, which increases genomic instability and is a hallmark of cancer. However, this was only the case for long-term NS workers, further implicating central adiposity as a risk factor for developing certain cancers in individuals exposed to circadian disturbance. Future research should determine other factors associated with DNA damage in this population. Support (if any) BCS: Andy Hill CARE Fund SG: NIH award R01ES030113.
Blanco et al. (Fri,) studied this question.