The mediating effect of BMI on the increased prevalence of metabolic syndrome among workers with occupational stress

The aim was to investigate the mediating effect of BMI on the relationships between occupational stress and metabolic syndrome in workers. In a cross-sectional study of 841 petroleum refinery workers in Hainan, South China, a self-designed questionnaire was used to collect baseline/occupational data and the Effort–Reward Imbalance (ERI) questionnaire was used to assess occupational stress. Trained physicians measured height, weight, abdominal circumference, and blood pressure; lipid profiles and fasting glucose levels were analyzed biochemically. Metabolic syndrome (MetS) was diagnosed using the NCEP-ATP-III criteria. In this study, correlations between BMI and MetS were analyzed between groups with and without occupational stress, and a mediation analysis was performed to examine the role of BMI in the relationship between occupational stress and MetS. The median age of the 841 participants was 31 (25 ~ 37) years, and the median length of service was 8 (2 ~ 15) years. There were 733 males (87.16%) and 108 females (12.84%). The median age and work tenure of the male workers were 32 (25 ~ 37) years and 9 (2 ~ 16) years, respectively, and those of the female workers were 26 (24 ~ 31) years and 2 (2 ~ 8.75) years, respectively. Among the workers, 268 and 573 did and did not experience occupational stress. The prevalence of MetS was greater (OR = 1.666, 95% CI: 1.039 ~ 2.671) and the BMI was greater (β = 0.684, 95% CI: 0.100 ~ 1.269) in those with occupational stress. Moreover, the BMI was significantly greater in the MetS group than in the non-MetS group (β = 1.299, 95% CI: 1.217 ~ 1.386). The mediation analysis confirmed no significant direct effect of occupational stress on MetS (direct effect, 95% CI: -0.074 ~ 0.009); however, the effect was significant when mediated by BMI (indirect effect, 95% CI: -0.029~-0.003). Occupational stress is associated with an increased prevalence of MetS and elevated BMI in workers. A positive correlation between BMI and the prevalence of MetS was observed. Furthermore, BMI may mediate the effect of occupational stress on the increased prevalence of MetS. However, this study is a cross-sectional study; future longitudinal studies could further test the causal associations between these study variables.