Prevalence of obstructive sleep apnoea in patients with coronary artery disease

Obstructive sleep apnoea (OSA) is characterized by recurring upper airway collapse with continual respiratory effort during sleep, causing apnoea, a fall in arterial oxygen saturation, arousal and excessive daytime sleepiness. It is a common disorder, with an estimated prevalence of about 1-5% in the adult population. OSA is related to arterial hypertension, an essential risk factor for the development of coronary artery disease (CAD). Furthermore, a high dietary intake is a common risk factor for OSA as well as for CAD.

To investigate the prevalence of OSA in CAD patients.

A random sample of 50 patients (aged 61 +/- 6 years, body mass index 26.8 +/- 3.8 kg/m2) diagnosed to have CAD by coronary angiography was investigated prospectively. Respiration and nocturnal oxygen saturation were registered during one night. Snoring and daytime sleepiness were evaluated by a questionnaire.

In 25 patients the apnoea index was > 10/h sleep. Excessive daytime sleepiness was exhibited by eight of these patients. Nineteen of the patients with an apnoea index > 10/h participated in a full night polysomnography. The apnoea index was 17.0 +/- 10.9/h and the apnoea-hypopnoea index was 32.4 +/- 16.5/h sleep. The mean nadir oxygen saturation was 87.3 +/- 1.6% and the minimal oxygen saturation was 75.5 +/- 10.6%. For seven patients the apnoea index was > 20/h.

CAD patients have a high prevalence of OSA. Since obstructive apnoeas may trigger severe cardiac events such as myocardial ischaemia or ventricular tachycardias in CAD patients, the presence of OSA in these patients should be considered.