Hematocrit and risk for hypertension in middle-aged Japanese male office workers

The association of hematocrit with development of hypertension over 9 years was studied in 784 hypertension-free Japanese men aged 40 to 59 years. The age-adjusted relative risk for hypertension above the borderline level and definite hypertension increased in a dose-dependent manner as hematocrit level increased (P for trend: 0.007 and 0.001, respectively). After controls for other potential factors of hypertension, the test for trend across increasing categories of hematocrit level remained as statistical significance for definite hypertension (P=0.015). The multivariate-adjusted relative risk for definite hypertension compared with less than 43.8% of hematocrit level was 1.29 [95% confidence interval (CI): 0.62-2.67] for 43.8 to 45.2% hematocrit level, 1.35 (95% CI: 0.62-2.95) for 45.3 to 46.3% hematocrit level, 1.96 (95% CI: 0.97-3.97) for 46.4 to 48.1% hematocrit level, and 2.06 (95% CI: 1.02-4.15) for 48.2% or more hematocrit level. These results suggest that hematocrit is closely associated with development of hypertension in middle-aged Japanese men.