Night shift work and its interaction with sleep duration and chronotype, and risk of cardiovascular-kidney-metabolic diseases in the UK Biobank

Abstract Aims Non-standard work schedules are becoming increasingly prevalent, with one in five workers participating in nightshifts. Whether working nightshifts is associated with cardiovascular-kidney-metabolic (CKM) outcomes, and whether chronotype or sleep duration moderate this association, remains unclear. Methods Our analysis is based on 96 365 UK Biobank participants (57% female, mean age 62 years), with information on employment history, tracking CKM incidence (cardiovascular diseases, chronic kidney diseases and/or type 2 diabetes) up to 2022. Cox proportional hazards models calculated hazard ratios (HR) adjusted for multiple potential confounders, and their 95% confidence intervals (CIs). Results With data on 5 967 incident cases, participants with over 20 years of night shift work had a significantly higher risk of CKM (HR=1.32 [95% CI, 1.20-1.45]) compared to day workers, after adjustment for confounders including sex, age, ethnicity, socioeconomic factors. Similarly, risk was higher than day workers among those working 8+ nightshifts per month (HR=1.32 [95% CI, 1.21-1.43]) and over 1200 lifetime nightshifts (HR=1.36 [95% CI, 1.25-1.48]); all Ptrend<0.001. The association between nightshift work and CKM risk was significantly modified by sleep duration, with higher risks among short sleepers (≤6 hours) (Pinteraction= 0.009, 0.031, and 0.017, respectively, for nightwork duration, intensity, and cumulative number of nights worked), but not by chronotype. Conclusion Our findings reveal a dose-response relationship between night shift work and CKM disease, further amplified by short sleep. Future research should continue to adopt CKM conditions as a composite outcome and investigate further how sleep characteristics may modify the impact of night shift work.