Int J Epidemiol. 2026 Jun 24;55(4):dyag114. doi: 10.1093/ije/dyag114.
ABSTRACT
BACKGROUND: It has been hypothesized that the incidence of cryptorchidism may have increased in Japan following the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in March 2011; however, empirical evidence remains limited. This study aimed to assess the possible impact of the accident on cryptorchidism incidence over an extended period of time before and after the accident.
METHODS: Detailed information on all patients who underwent orchiopexy between April 2008 and March 2021 was obtained from the medical records of 86 hospitals in Fukushima Prefecture. Interrupted time series analyses were performed to evaluate the immediate post- versus pre-accident level change and the monthly post- versus pre-accident slope change in orchiopexy surgery rates and birth rates with cryptorchidism.
RESULTS: In total, 622 orchiopexy surgeries performed in Fukushima Prefecture during the study period were included. No significant increase was observed in the monthly orchiopexy surgery rate per 100 000 population in Fukushima Prefecture after the accident, in terms of either the immediate level change (incidence rate ratio [IRR], 1.21; 95% CI, 0.86-1.70) or the monthly slope change (IRR per month, 1.01; 95% CI, 0.99-1.04). The estimated monthly birth rate with cryptorchidism per 1000 live births in Fukushima Prefecture also showed no significant increase in either the immediate level change (IRR, 0.87; 95% CI, 0.52-1.44) or the monthly slope change (IRR per month, 1.01; 95% CI, 0.99-1.04).
CONCLUSIONS: Our study provided no evidence that the FDNPP accident increased the orchiopexy surgery rates or birth rates with cryptorchidism in Fukushima Prefecture.
PMID:42470134 | DOI:10.1093/ije/dyag114
