Occupational heat exposure, nighttime warming, and eGFR loss in petrochemical workers: a retrospective cohort study with metabolomic evidence.

Under the context of climate warming, whether rising nighttime temperatures modify heat-related kidney risks among industrial workers remains unclear. This retrospective cohort study included 2,148 petrochemical workers in southeastern China followed from 2013 to 2022. Occupational heat exposure was assessed using the wet-bulb globe temperature (WBGT) index based on workplace monitoring records, and eGFR loss was defined as a ≥30% reduction in estimated glomerular filtration rate from baseline. Nighttime temperature was derived from ERA5-Land hourly temperature data (20:00-07:00). Cox proportional hazards models were used to estimate associations, with interaction analyses evaluating effect modification by nighttime temperature indicators. Serum metabolomics were conducted to explore potential mechanisms. During 11,412 person-years of follow-up, 382 incident cases of eGFR loss were identified. Occupational heat exposure was associated with an increased risk of eGFR loss (HR = 1.44, 95% CI: 1.16-1.79; P = 0.001). Over the past three decades (1993-2022), nighttime temperature in the study region increased at a rate of 0.405 °C per decade. The association between occupational heat exposure and eGFR loss was stronger at higher nighttime warming rates (P for interaction < 0.001) and higher nighttime temperatures (P for interaction = 0.012). Metabolomic analyses revealed alterations in amino acid metabolism, energy metabolism, and tryptophan-related pathways. These findings suggest that occupational heat exposure was associated with an increased risk of eGFR loss, and this association may be amplified under warmer nighttime conditions. Impaired nocturnal thermal recovery and related metabolic disturbances may contribute to heat-related renal injury.