Procedure-specific temperature dependence and lag structure of urinary stone surgery: A nationwide open-data study in Japan, 2019-2024.

OBJECTIVES

To determine whether the seasonality of urinary stone surgery and its association with ambient temperature differ between surgical procedures and to compare the time lag between temperature and each procedure.

SUBJECTS AND

METHODS

We used the nationwide open data of the National Database of health insurance claims in Japan for fiscal years 2019-2024 (April 2019 to March 2025, 72 months). We counted monthly inpatient surgeries for extracorporeal shock wave lithotripsy (ESWL), ureteroscopic lithotripsy (URS), percutaneous nephrolithotomy (PCNL) and transurethral cystolitholapaxy and expressed them as a seasonal index of surgeries per business day normalized to a mean of 1 within each fiscal year. Observed monthly mean temperatures for 12 representative meteorological stations were correlated with the index at lags of -1 to +4 months.

RESULTS

A total of 71 791 ESWL, 320 863 URS, 71 272 cystolitholapaxy and 20 387 PCNL procedures were performed. Volume rose from summer to autumn and was lowest in winter for ESWL, URS and cystolitholapaxy. In the same month, the correlation with temperature was strongest for ESWL (r = 0.83, 95% CI 0.74-0.89), followed by URS (r = 0.43, 0.22-0.60) and cystolitholapaxy (r = 0.35, 0.13-0.54), whereas PCNL showed no association (r = 0.05, -0.19-0.27). The correlation peaked at 1 month for ESWL (r = 0.87), at 2 months for URS (r = 0.69) and cystolitholapaxy (r = 0.52) and at 3 months for PCNL, where it was not significant at any lag. PCNL showed significant month-to-month variation that was not explained by temperature.

CONCLUSION

The seasonality of urinary stone surgery and the time lag relative to ambient temperature differ by procedure, being shortest for ESWL and longer for procedures requiring anaesthesia and hospitalization, while PCNL shows no association with temperature.