Serum uric acid and estimated glomerular filtration rate in working-age males: a 10-year longitudinal study of annual health check-up data from an occupational cohort in Japan

Background Maintaining kidney health before the onset of chronic kidney disease (CKD) is an important goal in nephrology and preventive medicine. Serum uric acid (SUA) levels have been associated with kidney dysfunction; however, evidence from long-term repeated-measures studies in working-age cohorts undergoing routine health check-ups remains limited. This study aimed to examine the longitudinal association between time-varying SUA levels and estimated glomerular filtration rate (eGFR) across the 10-year follow-up using annual health check-up data from an occupational cohort in Japan. Methods A retrospective longitudinal study was conducted using annual health check-up data from 5403 working-age males in an occupational cohort in the Kansai region of Japan, composed primarily of manufacturing-sector employees. The primary complete-case analysis included 56,816 observations from 5402 participants. eGFR was calculated at each annual health check-up. The longitudinal association between time-varying SUA and concurrently assessed eGFR was examined using linear mixed-effects models that included participant-specific random intercepts and participant-specific random slopes for measurement wave and SUA. The primary model was adjusted for demographic, clinical, and lifestyle factors as time-varying covariates. Sensitivity analyses included multiple imputation and alternative exposure and outcome measures. Results At baseline, the mean age was 46.5 years, the mean SUA level was 6.1 mg/dL, and the mean eGFR was 79.1 mL/min/1.73 m². Over the 10-year follow-up period, the mean eGFR declined to 70.1 mL/min/1.73 m², whereas the mean SUA level changed from 6.1 to 6.2 mg/dL. In the primary model, each 1 mg/dL higher SUA level was associated with a 3.25 mL/min/1.73 m² lower eGFR (95% confidence interval, − 3.34 to − 3.16; p < 0.001). These findings were consistent across sensitivity analyses. Conclusions In this occupational cohort of working-age males, a higher SUA level was longitudinally associated with lower eGFR. These findings suggest that SUA may provide additional information for interpreting eGFR levels and their longitudinal changes in health check-up settings. Further studies are warranted to determine its utility as an epidemiological marker in kidney function assessment in occupational health settings. Trial registration Not applicable.