Night shift work and biological ageing among hospital female nurses

Abstract

BACKGROUND AND AIM: The link between night shift (NS) work and biological ageing is supported by associations observed between NS work, increased risk of age-related diseases (e.g., cardiovascular diseases and cancer), and gene-specific methylation changes. We aim to verify whether NS work can influence biological age, estimated through a parsimonious epigenetic signature (proposed by Zbieć-Piekarska and colleagues). METHODS: Forty-six female nurses of the Policlinico Hospital (Milan, Italy) working in NS for at least two years were matched by age and length of employment with 51 female colleagues not working in NS. Sociodemographic and work-related information was collected through a semi-structured interview. Work-related stress was assessed through the Effort Reward Imbalance (ERI) questionnaire. Each subject provided written informed consent and donated a 12 ml blood sample. Biological age was calculated considering the methylation pattern of five CpG sites in five genes (ELOVL2, C1orf132/MIR29B2C, FHL2, KLF14, TRIM59). Age acceleration was estimated by regressing biological age on chronological age and taking the residuals. Multivariate linear regression models were applied. RESULTS:Biological ageing was not associated with working in NS or number of years in NS. Only subjects with overweight/obesity showed an increase in age acceleration per each year in NS (β=0.46, 95%CI: 0.05; 0.87, p=0.03, p-interaction=0.097). A similar pattern was observed for subjects experiencing work-related stress (ERI1), with an age acceleration of 0.58 years (95%CI: 0.10; 1.06, p=0.018, p-interaction=0.056) per each year in NS. We observed a higher age acceleration (β=0.66, 95%CI: 0.03; 1.29, p=0.041) when considering both categories combined (BMI≥25 and ERI1), even if no formal interaction was apparent. CONCLUSIONS:Although based on a small number of subjects, our findings suggest an increased biological ageing only among hypersusceptible subjects. This finding is worth of further investigation, also in light of recent results suggesting a higher breast cancer risk in women with increased age acceleration. KEYWORDS: working schedule, epigenetics, biological ageing, DNA methylation, overweight/obesity, work-related stress