Haematocrit and the risk of developing end-stage renal disease.

BACKGROUND: Anaemia is common in patients with renal failure; however, it is not known whether haematocrit level in the general population is a predictor for developing end-stage renal disease (ESRD). METHODS: A retrospective analysis was conducted to assess the development of ESRD within a population of 71 802 subjects (37 190 men and 34 612 women), 20-99 years, in Okinawa, Japan. Haematocrit data were collected between April 1983 and March 1984 and the subjects were followed forward to the year 2000 whether they were identified in the Okinawa Dialysis Study registry for identification of ESRD. Multivariate logistic analyses were performed to analyse the influence of haematocrit on the development of ESRD after adjusting for age, sex, blood pressure, body mass index, proteinuria and haematuria. In a subgroup of the cohort, similar analyses were repeated adjusting for estimated creatinine clearance by the method of Cockcroft and Gault. RESULTS: The mean (SD) level of haematocrit at the time of screening was 45.3% (3.3%) for men and 38.8% (3.2%) for women. During the 17-year follow-up, 269 patients (171 men and 98 women) were identified with ESRD. The mean time to onset of ESRD was 130.4 (53.6) months. The adjusted odds ratio and 95% confidence interval (CI) for the influence of haematocrit (%) on the development of ESRD was 0.991 and 0.988-0.995 (P<0.0001), suggesting that the lower haematocrit, the greater was the risk of developing ESRD. This finding was repeated in the subgroup analysis that included calculated creatinine clearance (adjusted odds ratio 0.991 and 95% CI 0.984-0.997, P=0.0057). In women, the adjusted odds ratio for haematocrits of 20.0-34.9% was 3.086 (CI 1.770-5.376, P<0.0001) when compared with the reference haematocrits of 35.0-39.9%. In men, the adjusted odds ratio for haematocrits of 25.0-39.9% was 1.927 (CI 1.418-2.625, P<0.0001) when compared with the reference haematocrits of 45.0-49.9%. CONCLUSIONS: Subjects with low haematocrits, <40% for men and <35% for women, have a significantly increased risk of ESRD.