Previous studies of sleep and breathing suggest an independent association between coronary artery disease (CAD) and obstructive sleep apnoea (OSA) in middle-aged males and females. These studies, however, were criticized because they did not properly adjust for all important confounding factors. In order to better control for the impact of these confounders, a case-control study was performed, matching for age, sex and body mass index (BMI), and additionally adjusting for hypertension, hypercholesterolemia, diabetes mellitus and current smoking. A consecutive selection of 62 patients (44 males and 18 females, mean age 69 yrs, range 44-88 yrs) requiring intensive care for angina pectoris or myocardial infarction at the County Hospital of Skaraborg, Skövde, Sweden, as well as 62 age-, sex- and BMI- matched control subjects without history or signs of heart disease underwent an overnight sleep/ventilatory monitoring study. The time interval between discharge from the intensive care unit and the overnight study ranged between 4 and 21 months. OSA, defined as a Respiratory Disturbance Index (RDI) of > or =10 x h(-1), was present in 19 CAD patients but only in eight control subjects (p=0.017). Using a univariate logistic regression analysis, current smoking (odds ratio (OR) 8.1, 95% confidence interval (CI) 2.2-29.0), diabetes mellitus (OR 4.2, 95% CI 1.1-16.1) and OSA (OR 3.0, 95% CI 1.2-7.5), but not hypertension (OR 1.5, 95% CI 0.7-3.2) and hypercholesterolaemia (OR 1.8, 95% CI 0.7-4.1) were significantly correlated with CAD. In a multiple logistic regression model, current smoking (OR 9.8, 95% CI 2.6-36.5), diabetes mellitus (OR 4.2, 95% CI 1.1-17.1) and OSA (OR 3.1, 95% CI 1.2-8.3) all remained independently associated with CAD. In summary, these data suggest a high occurrence of obstructive sleep apnoea in middle-aged and elderly patients with coronary artery disease requiring intensive care, which should be taken into account when considering risk factors for coronary artery disease.