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

ObjectiveTo investigate the prevalence of hypertension and circadian blood pressure (BP) variations in patients with obstructive sleep apnoea–hypopnoea syndrome (OSAHS).MethodsPatients 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 (RN/D) and morning to evening mean BP (RM/E) ratios.ResultsHypertension 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 RN/D and RM/E ratios increased...