Epigenetic markers of adverse lifestyle identified among night shift workers

Background Epigenetic changes in the form of DNA methylation (DNAm) may act as biological markers of risk factors or adverse health states. We investigated associations between night shift work and established DNAm predictors of lifestyle, and compared them with those observed between night shift work and self-reported or conventionally-measured phenotypes. Methods In two cohort studies, Generation Scotland (GS) (n=7,028) and Understanding Society (UKHLS) (n=1,175), we evaluated associations between night shift work and four lifestyle factors (body mass index, smoking, alcohol, education) using both conventionally-measured phenotypes and DNA methylation-based scores proxying the phenotypes. DNA methylation-based measures of biological ageing were also generated using six established “epigenetic clocks”. Meta-analysis of GS and UKHLS results was conducted using inverse-variance weighted fixed effects. Results Night shift work was associated with higher BMI (0.79; 95%CI 0.02, 1.56; p=0.04) and lower education (−0.18; −0.30, −0.07; p=0.002). There was weak evidence of association between night shift work and DNAm scores for smoking (0.06, −0.03, 0.15; p=0.18) and education (−0.24; −0.49, 0.01; p=0.06) in fully adjusted models. Two of the epigenetic age measures demonstrated higher age acceleration among night shift workers (0.80; 0.42, 1.18; p<0.001 for GrimAge and 0.46; 0.00, 0.92; p=0.05 for PhenoAge). Conclusions Night shift work is associated with phenotypic and DNAm-based measures of lower education. Night shift work was also related to DNAm predictors of smoking and ageing. ### Competing Interest Statement REM has received speaker fees from Illumina and is an advisor to the Epigenetic Clock Development Foundation.