Sex-specific bladder cancer incidence trends and generational effects in Spain.

Introduction: This study aimed to assess long-term trends in bladder cancer incidence in Spain from 1992 to 2021, using Age-Period-Cohort (A-P-C) modelling to disentangle the contributions of age, period, and cohort effects.

Methods: An ecological trend study was conducted using data from the Global Burden of Disease (GBD) 2021 Study via the Global Health Data Exchange. Age- and sex-specific incidence counts for Spain (1992-2021) were analyzed. Joinpoint regression estimated annual percent changes (APCs) and average annual percent changes (AAPCs). A-P-C modelling assessed net and local drifts, as well as cohort and period rate ratios using 5-year age groups and calendar periods.

Results: From 1992 to 2021, 377,430 male and 66,191 female BC cases were estimated. In men, age-adjusted incidence declined (AAPC = -0.6 %), driven by favourable birth cohort and period effects. In women, a modest decline (AAPC = -0.3%) masked a mid-century cohort effect, with increased risk in those born between 1957 and 1967-consistent with a delayed tobacco epidemic. Incidence rose with age in both sexes, though male-to-female incidence ratios narrowed in older groups.

Conclusion: BC incidence in Spain reflects complex, sex-specific temporal dynamics. While male incidence is decreasing, women show persistent cohort-specific increases. These trends underscore the importance of sex-sensitive public health strategies targeting modifiable risk factors, particularly tobacco use.