Objective: To assess whether sleep apnoea syndrome is an independent risk factor for hypertension.

Design: Population study.

Setting: Sleep clinic in Toronto.

Participants: 2677 adults, aged 20-85 years, referred to the sleep clinic with suspected sleep apnoea syndrome.

Outcome measures: Medical history, demographic data, morning and evening blood pressure, and whole night polysomnography.

Results: Blood pressure and number of patients with hypertension increased linearly with severity of sleep apnoea, as shown by the apnoea-hypopnoea index. Multiple regression analysis of blood pressure levels of all patients not taking antihypertensives showed that apnoea was a significant predictor of both systolic and diastolic blood pressure after adjustment for age, body mass index, and sex. Multiple logistic regression showed that each additional apnoeic event per hour of sleep increased the odds of hypertension by about 1%, whereas each 10% decrease in nocturnal oxygen saturation increased the odds by 13%.

Conclusion: Sleep apnoea syndrome is profoundly associated with hypertension independent of all relevant risk factors.