Dissociation between subjective sleep quality and lipid dysregulation in underground miners: night shift work as an...

Shift work disrupts circadian rhythms and is established as a risk factor for metabolic syndrome. While poor sleep quality is often hypothesized as the primary mediator linking shift work to dyslipidemia, the extent to which circadian misalignment affects lipid metabolism independently of sleep complaints remains unclear. This study aimed to investigate the independent and combined effects of shift work and sleep quality on serum lipid profiles in a cohort of male underground miners.

A cross-sectional analysis was conducted on 921 male miners from the Kailuan Group. Participants were categorized by work schedule into Night Shift (0:00-7:59, n = 326) and Day/Morning Shift (8:00-23:59, n = 595) groups to ensure distinct circadian exposure profiles. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI), with a score >5 defining poor sleep. Fasting serum lipids-Total Cholesterol (TC), Triglycerides (TG), High-Density Lipoprotein Cholesterol (HDL-C), and Low-Density Lipoprotein Cholesterol (LDL-C)-were quantified. General Linear Models (GLM) and interaction analyses were employed to assess associations, adjusting for age, education, smoking, and alcohol consumption.

Night shift workers exhibited significantly higher global PSQI scores compared to day workers (4.70 ± 3.06 vs. 3.59 ± 2.71, P < 0.001). While the overall prevalence of dyslipidemia did not significantly differ (32.52% vs. 27.57%, P = 0.114), night shift work was significantly associated with elevated mean TC levels (5.36 ± 2.83 vs. 5.09 ± 1.09 mmol/L, P = 0.039) independent of covariates and occupational factors. Surprisingly, subjective sleep quality (PSQI) showed no significant correlation with lipid parameters (All P > 0.05). In the stratified interaction analysis, the highest TC levels were observed in the "Night Shift + Good Sleep" subgroup (5.51 ± 3.43 mmol/L), significantly differing from the "Day Shift + Good Sleep" reference group (4.96 ± 1.06 mmol/L, P = 0.039).

Night shift work is associated with elevated total cholesterol in male miners, an effect that persists even among those reporting good sleep quality. This suggests that circadian misalignment governs lipid dysregulation via pathways distinct from subjective sleep disruption. Occupational health interventions should target circadian phase management beyond basic sleep hygiene education.