Sleep-disordered breathing (SDB) is a recognized risk factor for excessive daytime sleepiness (EDS) and hypertension, but evidence of this association in Asian women is limited. We conducted a cross-sectional study of 3,568 women aged 30-69 years living in three Japanese communities. The 3% oxygen desaturation index (ODI) was selected as the indicator of SDB, and blood oxygen fall was estimated by overnight pulse oximetry. The prevalence of SDB was 20.2% for 3% ODI>or=5, 6.4% for 3% ODI>or=10, and 2.8% for 3% ODI>or=15 among Japanese women aged 30-69 years. The 3% ODI was positively associated with the prevalence of self-reported EDS and mean values of systolic and diastolic blood pressure levels. The multivariate odds ratios for 3% ODI of 5-9, 10-14, and >or=15 in reference to 3% ODI<5 were 1.9 (1.2-3.0), 2.2 (1.0-4.6), and 1.8 (0.7-4.4) (p for trend=0.01), respectively, for EDS and 1.1 (0.9-1.4), 1.2 (0.8-1.8), and 2.2 (1.4-3.4) (p for trend<0.001), respectively, for hypertension. The severity of SDB was significantly associated with EDS and hypertension among Japanese women.