Evening–Morning Differences in Blood Pressure in Sleep Apnea Syndrome: Effect of Gender

Background Obstructive sleep apnea (OSA) is associated with hypertension. In the current study we sought to determine whether the evening–morning differences in blood pressure (BP) would correlate with the severity of OSA and whether there are gender-related differences. Methods A total of 2009 consecutive patients referred to sleep examination because of suspected sleep apnea were retrospectively included. The patients comprised 1566 men, of whom 870 were nonhypertensive (non-HT) and 696 hypertensive (HT) and 443 women, of whom 258 were non-HT and 185 HT. Four BP measurements, two in the evening and two in the morning, were taken. The relationship between evening–morning differences in BP and the number of apneas/hypopneas divided by hours of sleep (AHI) were analyzed separately for HT and non-HT men and women. Results In men, increase in AHI was associated with increase in morning BP, and the evening–morning difference for both systolic and diastolic BP became negative. These trends were found to be significant by linear regression analyses both for HT (for systolic BP, r = 0.75, P< .05, for diastolic BP r = 0.96, P< .05) and non-HT patients (for systolic BP r = 0.93, P< .05, for diastolic BP r = 0.94, P< .05). In women (unlike in men), increasing AHI was not associated with a linear increase in the evening–morning BP differences. None of the regression lines fitted to the data was significant. Conclusions Our results demonstrate that the evening to morning difference in BP in men with OSA is linearly related to the severity of OSA, both in patients with HT and in those with non-HT. These results may have practical relevance in screening for patients with OSA and may have prognostic clinical value in predicting future cardiovascular events.