Night work nearly doubles risk of type 2 diabetes and elevates fasting glucose over time

Aim/background: This study aimed to evaluate the association of night shift work with incident type 2 diabetes (T2D) risk and longitudinal fasting blood glucose (FBG) trajectories in an Algerian occupational cohort, leveraging pre-employment medical data as a standardized baseline. Methods: This cross-sectional study recruited 600 workers during their 2019 periodic medical examination. Longitudinal clinical data, including FBG measurements, were retrospectively collected from their occupational health records, specifically from their initial employment medical examination (baseline) and three subsequent annual visits (2017-2019). The difference in FBG (DFBG) was calculated as the mean follow-up FBG minus baseline FBG. Multivariable logistic regression was used to model incident T2D (diagnosed post-recruitment), adjusting for age, seniority, and baseline body mass index (BMI). Linear regression was employed to analyze DFBG, adjusting for age and seniority. Results: The study population was predominantly male (sex ratio = 4.35) with a mean age of 41.2 ± 8.13 years. Of these workers, 238 (39.7%) engaged in night work either through shift or on-call arrangements. Night workers were significantly older than their daytime counterparts (42.9 ± 7.77 years vs. 40.0 ± 8.14 years ; p < 0.001). Workplace seniority averaged 11.32 ± 7.36 years. The prevalence of diabetes was 11.66%. Night workers had a significantly higher incident T2D (14.7% vs. 8.0% ; p = 0.009). After adjustment, night work was associated with a nearly two-fold increased risk of incident T2D (adjusted OR = 1.97 [95% CI 1.08–3.6] ; p = 0.026). Night workers also exhibited a steeper longitudinal rise in FBG (DFBG coefficient B = 0.05 [95% CI: 0.019–0.08] ; p = 0.001). Conclusion: These findings are consistent with international evidence suggesting that night work disrupts circadian rhythms, contributing to metabolic dysregulation and increased diabetes risk. Specifically, night work was independently associated with a nearly two-fold increased risk of incident T2D and accelerated glycemic deterioration over time, underscoring the need for targeted metabolic monitoring in this high-risk group. Key study limitations include its reliance on a cross-sectional design for risk estimation and the absence of data on lifestyle confounders.