Shift work and TyG-metabolic obesity indices on hypertension incidence among male steelworkers: a prospective cohort study

Male steelworkers face elevated hypertension risk due to shift work and occupational exposures. However, the impact of TyG-related metabolic obesity indices on steelworkers remains unclear. This study focused on five TyG metabolic obesity indices (TyG-WWI, TyG-WHtR, TyG-BMI, TyG-WC, TyG-CVAI). It assessed their independent effects, interactions with shift work, mediating roles in hypertension in this population. This prospective cohort study included 4,345 male steelworkers in Tangshan, China. Baseline surveys were completed between March and September 2017, and participants were followed up until December 2024. Data were collected through questionnaires, physical examinations, and laboratory tests. Multivariate Cox regression and restricted cubic spline (RCS) analyses were used to assess associations and dose-response relationships between shift work, TyG-metabolic obesity indices, and hypertension incidence. Interaction analysis evaluated multiplicative and additive effects between the weighted shift index (WSI) and TyG-metabolic obesity indices, while mediation analysis examined their mediating role. Subgroup analysis, sensitivity analysis, and weighted quantile sum (WQS) regression were performed to reinforce reliability and quantify risk weights. During the 7-year follow-up, 1,685 new cases of hypertension occurred (cumulative incidence: 38.78%). Current shift work, three-shift rotation, WSI ≥ 2798.41, and high TyG-metabolic obesity index scores were all significantly associated with increased hypertension risk (HR: 1.304–2.609, all P < 0.001). Both WSI and TyG-metabolic obesity indices exhibited nonlinear positive correlations with hypertension, suggesting the presence of risk thresholds. TyG-CVAI carried the highest weight (32.85%) in WQS analysis. WSI exhibited significant multiplicative interactions with most TyG-metabolic obesity indices (WSI Q4 * TyG-CVAI Q4: HR = 1.650, P < 0.001). TyG-WWI and TyG-CVAI partially mediated the relationship (mediation effect proportions: 27.352%, 27.497%). Hypertension risk among male steelworkers is closely associated with WSI and TyG-metabolic obesity indices, exhibiting threshold effects and synergistic interactions. TyG-WWI and TyG-CVAI mediate the pathway linking shift work to hypertension. WSI and TyG-CVAI should be incorporated into risk assessment frameworks, with priority given to routine monitoring of triglycerides, fasting blood glucose, HDL-C and related markers.