Non-dipping blood pressure in normotensive patients with obstructive sleep apnea

ABSTRACT

To investigate circadian blood pressure profiles in normotensive patients with moderate to severe obstructive sleep apnea [OSA], in relation to their apnea indices and left ventricular parameters, we studied twenty one male patients with clinic blood pressures of< 140/90 mmHg. They were matched for age and body mass index [BMI] and all were heavy snorers. They underwent overnight polysomnography, 24 h non-invasive arterial blood pressure monitoring [ABPM] and echocardiography. Patients with a nocturnal reduction in average daytime systolic and diastolic blood pressure of less than 10% were considered non-dippers. Nine patients were non-dippers and 12 were dippers. In the non-dipper group asleep systolic and diastolic blood pressure were significantly higher than in the dipper group, [P< 0.0001 and P<0.01 respectively]. There were no significant differences between the apnea/hypopnea [AHI] and the oxygen desaturation [ODI] indices of the dipper and the non-dipper groups. However, left ventricular parameters were significantly higher in the non-dipper than in the dipper group left ventricular mass index [LVMI, P<0.001], posterior wall thickness [PWT, P<0.001], interventricular septal thickness [IVST, P<0.001] and relative wall thickness [RWT, P<0.01]. In this preliminary study an absent or reduced blood pressure fall during sleep in normotensive patients with moderate to severe OSA cannot be explained by the severity of the apnea alone. Left ventricular hypertrophy, though may be a sequel to the non-dipper situation may also be the cause of it