Overactive bladder (OAB) is a highly prevalent condition in both sexes. As the studies addressing the long-term trend prevalence of OAB are limited in Japan, we conducted a retrospective analysis to examine the ten-year trend prevalence of OAB using a large-scale medical claims database in Japan.

The medical reimbursement data between January 2009 and December 2018 were provided by Japan Medical Data Center, Inc. The diagnosis of OAB was identified through the International Classification of Diseases 10th revision code for unspecified urinary incontinence (ICD10: R32) initially, which was further confirmed based on the Japanese standardized disease name of OAB assigned to this code. The adult patients aged less than 75 years were included, and the suspected cases were excluded. The annual prevalence was estimated for each calendar year. The age-adjusted prevalence was calculated separately for men and women based on the Japanese demographic statistics in the 2013 census.

During the ten-year study period, there were 5,033,824 registrants enrolled. Of 70,140 patients with OAB diagnosis, the suspected cases were excluded, and a total of 59,666 patients were eligible for the study. In Figure 1, the most dramatic rise in OAB prevalence was noted in the oldest age group of 70-74 years from 3.61% in 2009 to 6.29% in 2018. A moderate increase was also observed in the 50s and the 60s age group, while those under the 40s age group remained relatively constant under 1% throughout the study period. In Figure 2, the age-adjusted OAB prevalence among the whole study cohort and those aged above the 40s are shown. Prior to 2016, OAB prevalence remained higher among males than females in both; however, the prevalence in females exceeded that of males afterwards. The OAB prevalence in females over 40s increased the most by two-folds from 0.99% in 2009 to 2.22% in 2018.

The prevalence of OAB is thought to be rising, but updated data are lacking in Japan. The present data on the prevalence of OAB can be used to describe the importance of OAB, especially in the older population, as the incremental rise was evident with increased age. We recognize that factors such as increased disease awareness of OAB in patients through media engagement and healthcare programs, and increased desire for quality-of-life improvement may have contributed to the overall rise in the prevalence of OAB in this study. These might have been induced and accelerated by the enhanced options in pharmacological treatments; a number of new anticholinergics and therapeutic formulations, such as orodispersible tablets and transdermal patches were introduced mainly in the first half of the ten-year period.

The present study revealed that the prevalence of OAB appears to be steadily increasing in Japan during the past decade. Further research is needed to investigate the factors contributing to the observable change in the prevalence of OAB in this population.