Birth cohort effects in incident renal replacement therapy in Japan, 1982-2021

This study aimed to investigate the long-term trends of incident end-stage kidney disease (ESKD) requiring renal replacement therapy (RRT) in Japan using age-period-cohort analysis and evaluated birth cohort effects for incident ESKD requiring RRT.

The number of incident RRT patients aged between 20 and 84 years by sex from 1982 to 2021 was extracted from the Japanese Society of Dialysis Therapy registry data. Annual incidence rates of RRT were calculated using census population as denominators, and changes in the incidence rates were evaluated using an age-period-cohort model. The age and survey year period categories generated 20 birth cohorts with 5-year intervals (from 1902-1907 to 1997-2001).

The incidence rates of RRT in both sexes initially rose in the birth cohorts born in the early 1900s, and then decelerated and peaked during 1940-1960s in men and 1930-1940s in women, following a steady decline in both sexes. Compared with the reference 1947-1951 birth cohort, the highest cohort rate ratio was 1.14 (95% CI, 1.04-1.25) in the 1967-1971 birth cohort in men and 1.04 (95% CI, 0.98-1.10) in the 1937-1941 birth cohort in women.

Significant cohort effects were identified in both sexes, but the peak of RRT was different for each sex. Our findings suggest that men born between 1940 and 1960s and women born between 1930 and 40 s may be important target populations to consider when decreasing incidence rates of RRT among the general Japanese population.