[Status of board-certified nephrologists of the Japanese Society of Nephrology among 47 prefectures].

To improve chronic kidney disease (CKD) outcomes, board-certified nephrologists of the Japanese Society of Nephrology (certified nephrologists) are anticipated to play an important role in community medicine and establish an effective cooperative relationship with primary care physicians. We analyzed the present status of certified nephrologists in each prefecture of Japan based on national data. As a result, in 2008, the maximum number of certified nephrologists per population among the 47 prefectures was 5.3 times higher than the minimum number. The rate of increase was not high in prefectures with a small number of certified nephrologists per population, which indicates that the disparities among the prefectures will persist in the future. To analyze how certified nephrologists participate in the community medicine of the 47 prefectures of Japan, we performed an ecological regression study. At first, it was shown that the number of certified nephrologists per resident population according to prefectures in 2007 had no significant correlation with the annual amount paid for angiotensin converting enzyme inhibitor (ACEI), angiotensin II receptor blocker (ARB), calcium channel-blocker (CCB), or erythropoiesis stimulating agent (ESA) per resident. Furthermore, to determine what parameters had a significant correlation with the incidence of dialysis in each prefecture, simple linear regression analysis was first performed. As a result, parameters with a significant correlation were the average age of the inhabitants, and the annual amounts paid for ARB, ARB plus ACEI, CCB, and ESA per resident. Furthermore, multiple regression analysis revealed that there were two variables included in the final model which could explain the low incidence of dialysis in each prefecture. One was the annual amount of ESA used for predialysis CKD patients, and the other was the number of certified nephrologists per population. Based on these findings, although our ecological study cannot identify causation, we predict that certified nephrologists can effectively prevent the progression of CKD, and an increase in certified nephrologists will decrease the incidence of dialysis.