Impact of shift work and obesity on risk of hyperuricemia in coal miners: A cross-sectional design based dose-response relationships and interaction analysis

Background The prevalence of hyperuricemia (HUA) among Chinese residents has been increasing annually, with occupational populations facing a higher risk of HUA due to shift work or obesity.

Objective To investigate the impact of shift work and obesity on HUA among coal miners, and to provide scientific data for the prevention of HUA in this occupational group.

Methods A cross-sectional study was conducted with 25619 workers from a coal mining group in 2023 as the study population, using a questionnaire survey and occupational health check-ups. Workers who were retired or on medical leave, as well as those who provided incomplete responses to the questionnaire or did not complete anthropometric measurements or blood tests, were excluded. A total of 23173 participants were included in the study. An unconditional logistic regression model was used to analyze the association between HUA and selected factors such as shift work status, years of shift work, daily shift work hours, body mass index (BMI), waist-to-height ratio (WHtR), and visceral adiposity index (VAI), as well as the interaction between obesity and shift work on HUA. Restricted cubic spline functions were used to analyze the dose-response relationship between years of shift work, daily shift work hours, and HUA.

Results The average age of the included workers was (42.38 ± 9.82) years. A total of 6735 workers reported positive HUA, with a positive rate of 29.1%, and the prevalence was higher in men compared to women (31.8% vs. 13.9%). After adjusting for confounding factors, the restricted cubic spline model revealed a nonlinear dose-response relationship between years of shift work, daily shift work duration, and HUA: ① When the years of shift work exceeded 3.25 years, the risk of HUA in workers gradually increased with longer work duration. At 20 years of shift work, the risk increase showed a "saturation effect," meaning that the risk of HUA no longer increased with additional years of shift work. ② When daily shift work duration was below 10 h, the risk of HUA increased with the length of shift work, but after exceeding 10 h, the risk stabilized. After adjusting for confounding factors, the logistic regression model showed that, compared to non-shift workers, shift workers, those with 10-20 years and over 20 years of shift work experience, as well as those working less than 8 h and more than 8 h per day, had a higher risk of HUA, with odds ratios (OR) of 1.14 (95%CI: 1.06, 1.22), 2.42 (95%CI: 2.20, 2.67), 2.23 (95%CI: 2.00, 2.48), 1.41 (95%CI: 1.29, 1.54), and 1.90 (95%CI: 1.75, 2.06), respectively. Additionally, compared to individuals with normal obesity indices, those with overweight and obesity based on BMI, high and very high VAI and excessive WHtR had a higher risk of HUA, with ORs of 2.01 (95%CI: 1.85, 2.17), 3.51 (95%CI: 3.20, 3.84), 1.42 (95%CI: 1.32, 1.54), 2.10 (95%CI: 1.91, 2.30), and 1.82 (95%CI: 1.69, 1.97), respectively. The interaction analysis showed no interaction between shift work and obesity index (both P_s < 0.001).

Conclusion Shift work, longer shift work years, and longer daily shift work hours increase the risk of HUA among coal miners. Additionally, the role of obesity in the development of HUA cannot be ignored.