Association of duration of residence in the southeastern United States with chronic kidney disease may differ by race: the REasons for Geographic and Racial Differences in Stroke (REGARDS) cohort study
We previously showed that there are marked geographic differences in the incidence of end-stage renal disease (ESRD) within Japan. In addition, the use of renin–angiotensin system inhibitors was found to be inversely correlated with the increasing ESRD rate. It was recently demonstrated that the incidence of ESRD due to diabetic nephropathy is declining in both Europe and USA. Therefore, we investigated the increasing ESRD rate and its geographic difference in Japan. Each year, the Japanese Society for Dialysis Therapy reports the numbers of patients initiating maintenance dialysis therapy in each prefecture of Japan. We used old (1984–1991) and recent (2001–2008) data to compare the increasing ESRD rate, which was estimated from the slope of the regression line of the annual incidence corrected for population, between the two periods in 11 regions of Japan. Increasing ESRD rate almost halved, from 11.1 ± 5.6 to 5.4 ± 0.7/million per year from the old to the recent period. Deceleration of the increasing ESRD rate from the old to the recent period was correlated with the incidence in the old period across 11 regions (r = 0.81, p < 0.003); i.e., the deceleration was greater in the regions where ESRD incidence had been higher. Whereas the increasing ESRD rate was significantly different among regions in the old period, this was not the case in the recent period, resulting in uniformity throughout Japan. The increasing ESRD rate is slowing in Japan, and its geographic differences, previously observed, have disappeared.