The aim of the present study was to assess associations between obstructive sleep apnoea and insulin sensitivity in a population-based sample of females. In total, 400 females aged 20-70 yrs underwent a full-night polysomnography, fasting blood sampling, measurement of anthropometric variables and oral glucose tolerance test with measurement of the insulin response (n = 358). The apnoea/hypopnoea index (AHI) was calculated from the results of the polysomnography. From the results of the oral glucose tolerance test, an insulin sensitivity index (ISI) was calculated. Females with an AHI < 5 (n = 119) had a mean+/-SD ISI of 8.3+/-3.8, whereas females with an AHI > or = 30 (n = 34) had an ISI of 6.2+/-4.0. Nocturnal minimal saturation was independently associated with decreased insulin sensitivity when controlling for age, waist/hip ratio, level of physical activity, smoking and alcohol consumption (95% confidence interval (CI) 0.004-0.14). When adjusting for confounders, the AHI was associated with increased fasting and 2-h insulin levels (95% CI 0.14-0.99 and 95% CI 0.28-6.47, respectively). Obstructive sleep apnoea was found to be independently associated with decreased insulin sensitivity in the present population-based sample of females.