Night shift work increases the risk of irritable bowel syndrome, which is mediated by inflammation

Abstract Background The impact of long-term night shift work on the incidence of irritable bowel syndrome (IBS) is still largely unknown, and the underlying mechanism remains unclear. We aimed to investigate the association of night shift work with IBS risk and further explore whether low-grade inflammation mediated this relationship. Methods This cohort study included 239,760 participants who were in paid employment or self-employed from the UK Biobank. In-depth lifetime employment information was used to calculate duration and frequency of night shifts. Low-grade inflammation index (INFLA-score) was calculated from five circulating inflammatory biomarkers. Cox proportional hazard models were used to estimate the relationships between long-term night shift work and IBS risk, and mediation analyses were also performed. Results An increasing trend of IBS incidence was observed from day workers to regular night shift workers. Compared to day workers, rarely/some night shift workers (HR 1.097, 95% CI 1.007-1.195) and usual/permanent night shift workers (HR 1.213, 95% CI 1.046-1.407) had higher risk of IBS. Workers with longer duration (≥3 years) (HR 1.241, 95% CI 1.073-1.436) and higher frequency of night shifts (>7 shifts/month) (HR 1.248, 95% CI 1.045-1.491) also showed higher IBS risks. INFLA-score significantly mediated the association of long-term night shift exposure with increased IBS risk (mediation proportion 3.6%, P < 0.05). Conclusions Long-term exposure to night shift work is associated with a higher risk of IBS, the potential underlying mechanism may be the heightened low-grade inflammation. Key messages • Current night shift exposure, longer night shift duration and higher night shift frequency were significantly associated with higher risk of IBS. • Our findings indicate that night shift work may increase the IBS risk by triggering a cascade of low-grade inflammatory processes.