Sleep related hypoxaemia in hypertensive and normotensive men

An association between hypertension and obstructive sleep apnoea (OSA) has been found by some researchers but remains controversial. Since such an association would have important implications for the investigation and management of hypertension, the rate of nocturnal hypoxaemic episodes has been compared in hypertensive and normotensive men.

The study was carried out in the community in Belfast and its environs. Thirty four men with mild to moderate hypertension aged 40-64 years were identified from general practice and a hypertension clinic. Normotensive men, matched for age and body mass index, were selected from a community survey. Subjects answered a sleep questionnaire and underwent overnight pulse oximetry at home. Computer analysis of the results gave the number and magnitude of dips in oxygen saturation (SaO2 dips, 4% or greater).

The median number of SaO2 dips/hour for hypertensives was 2.0, and for normotensives was 0.8. Lowest SaO2 and mean SaO2 levels were significantly lower in the hypertensive group. Only one subject had a rate of SaO2 dips/hour greater than five and symptoms suggestive of OSA.

Both hypertensive and normotensive men had relatively few episodes of nocturnal hypoxaemia. The small increase in the rate of SaO2 dips in hypertensive subjects has not yet been fully explained. These results imply that OSA is not common in hypertensive subjects and is unlikely to be an important cause of hypertension.