Validity of a Risk Prediction Equation for CKD After 10 Years of Follow-up in a Japanese Population: The Ibaraki Prefectural Health Study

Background: Chronic kidney disease (CKD) is an important health problem for which risk equations have been developed for Western populations. This study aimed to develop and validate a risk prediction equation for CKD in a Japanese population.

Study Design: Observational cohort study.

Setting & Participants: The study included 135,007 participants who completed an annual health checkup in 1993 to 1996 in the Ibaraki Prefecture in Japan. Participants were initially free of CKD (defined as stage 3, 4, or 5 CKD or proteinuria [2+ or 3+] by dipstick). Follow-up information was available from health checkups 10 years after the initial evaluation. We used data from 40,963 women and 17,892 men in the northern region of the prefecture for the development of risk prediction equations and 53,042 women and 23,110 men in the southern region for external validation.

Predictors: Age, estimated glomerular filtration rate (eGFR), body mass index, proteinuria, hematuria, hypertension, diabetes mellitus, smoking, and drinking.

Outcome: Occurrence of CKD (defined as eGFR<60mL/min/1.73m and/or proteinuria [2+ or 3+] by dipstick).

Analytical Approach: Logistic regression analysis to estimate risk for CKD stratified by sex.

Results: During follow-up, 7,500 cases of CKD developed in the northern region and 8,964, in the southern region. Older age, proteinuria (1+), higher systolic blood pressure, medication for hypertension, and current smoking were associated with increased risk for CKD in both sexes, whereas higher eGFR and daily alcohol intake were associated with lower risk. C statistics of risk estimation equations for CKD at 10 years were >0.8 for both the development and external validation populations, and discrimination of the risk estimation was fairly good in women and men.

Limitations: Fluctuations in variables were not evaluated because the study used annual health checkups. This study excluded a large number of people for whom a 10-year health checkup was not available.

Conclusions: Estimations of risk for CKD after 10 years of follow-up in a general Japanese population can be achieved with a high level of validity.