Prevalence of hypertension and circadian blood pressure variations in patients with obstructive sleep apnoea–hypopnoea syndrome

OBJECTIVE: To investigate the prevalence of hypertension and circadian blood pressure (BP) variations in patients with obstructive sleep apnoea-hypopnoea syndrome (OSAHS). METHODS: Patients referred to a sleep clinic underwent polysomnography with measurement of BP at four time points. They were classified into four groups (control, and mild, moderate or severe sleep apnoea) using the apnoea-hypopnoea index (AHI). Circadian variation was assessed using night-time to daytime mean BP (R(N/D)) and morning to evening mean BP (R(M/E)) ratios. RESULTS: Hypertension was significantly more common in patients with OSAHS (50.5%) than in controls (30.4%). AHI was positively correlated with hypertension after controlling for related confounders. Mean BP values at all four time points rose with increasing AHI. The increase in night-time and morning values was more pronounced than the increase in daytime and evening values in patients with OSAHS, resulting in loss of the normal BP diurnal rhythm. The R(N/D) and R(M/E) ratios increased with increasing AHI. Daytime BP was significantly correlated with AHI and the lowest oxygen saturation value. CONCLUSION: OSAHS was shown to be an independent risk factor for hypertension. It was also associated with loss of the normal BP diurnal rhythm.