Association of night shift work and biological ageing: the mediating role of body mass index.

Background: We aimed to examine whether current and lifetime night shift work is associated with accelerated biological ageing and the potential role of body mass index (BMI) in mediating the association.

Methods: Data were sourced from the UK Biobank cohort. This study included participants who reported detailed information on their current work schedule and had complete data to calculate PhenoAge. The outcome of interest was biological ageing, measured by PhenoAge acceleration. Multivariable linear regression models were conducted to test the relationship between night shift work and biological ageing. Mediation analyses were performed.

Results: Of the 182 064 participants included, the mean age was 52.6 years, and 51.1% were male. After adjustment for chronological age and sex, compared with day workers, shift workers without night shift, irregular night shift workers and permanent night shift workers were associated with 0.59-, 0.87- and 1.30-year increase in biological ageing, respectively (P for trend <.001). Considering the lifetime work schedule, participants who worked night shifts >10 years and participants who worked >8 night shifts each month showed increased biological age acceleration [>10 years: β = 0.54, 95% confidence interval (CI) 0.29-0.79; >8 times/month: β = 0.29, 95% CI 0.07-0.50]. The mediation analysis showed that BMI mediated the associations between night shift work and biological age acceleration by 36%-53%.

Conclusions: We showed that night shift work was associated with accelerated biological ageing. Our findings highlight the interventions on appropriate shift work schedules and weight management in night shift workers, which may slow the biological ageing process and ultimately reduce the burden of age-related diseases.