The association between heat exposure, inflammation and hyperuricaemia among steelworkers

Occupational heat exposure is associated with the occurrence of hyperuricaemia. However, it is not clear how heat exposure affects hyperuricaemia.

To explore the mediating role of inflammatory indices in the relationship between heat exposure and hyperuricaemia among steelworkers.

A prospective cohort study comprising 3947 steelworkers was conducted. The Cox proportional hazards regression model was used to analyse the associations of heat exposure and inflammation with the incidence of hyperuricaemia. Generalized linear models were employed to examine the relationship between heat exposure and inflammation. Mediation analysis was performed to investigate the mediating role of inflammation in the association between heat exposure and hyperuricaemia among steelworkers.

The incidence of hyperuricaemia among steelworkers was 19.53%. Exposure to heat (HR = 1.76, 95% CI 1.50-2.06) was associated with an increased risk of hyperuricaemia. Compared with the group with the lowest inflammation level, the highest levels of Systemic Immune-Inflammation Index (SII) (HR = 2.01, 95% CI 1.71-2.61), Systemic Inflammatory Response Index (SIRI) (HR = 2.07, 95% CI 1.66-2.58) and Aggregate Index of Systemic Inflammation (AISI) (HR = 2.22, 95% CI 1.78-2.77) were associated with the highest incidence of hyperuricaemia. The SII, SIRI and AISI levels in the heat exposure group were 50.218, 0.148 and 47.237 units higher than those in the non-exposure group, respectively (P < 0.001). SII, SIRI and AISI exhibited mediating effects in the relationship between heat exposure and the incidence of hyperuricaemia, with mediation proportions of 12.93, 6.33 and 8.98%, respectively.

Inflammation is a partial mediator of the relationship between heat exposure and hyperuricaemia.