Impact of non-dipping on cardiovascular outcomes in patients with obstructive sleep apnea syndrome.

Obstructive sleep apnea syndrome (OSAS) is a risk factor for cardiovascular events. However, it is unclear how OSAS contributes to the events. We investigated the impact of non-dipping on the incidence of cardiovascular events in a retrospective cohort study comprising 251 patients with OSAS. OSAS was diagnosed by overnight polysomnography and all patients underwent 24-h ambulatory blood pressure monitoring. Non-dipping was diagnosed when reduction in sleep blood pressure was <10% of awake blood pressure. Over a mean 43-month follow-up period, 15 patients (6.0%) developed cardiovascular events including stroke, heart failure, and ischemic heart disease. Significantly higher cardiovascular events were observed in the non-dipping group than those without it by Kaplan-Meier analyses. Cox regression analysis revealed that the presence of non-dipping was significantly and independently associated with the incidence of cardiovascular events (hazard ratio, 3.88; 95% confidence interval, 1.19-17.41; p < 0.05), after adjusting for severity of OSAS, and CPAP therapy. Thus, non-dipping was a marker for a poor prognosis in patients with OSAS.

The relationship between morning hypertension and sleep quality in patients with obstructive sleep apnea syndrome.

This study aimed to investigate the prevalence of abnormal diurnal blood pressure (BP) profiles in patients with obstructive sleep apnea syndrome (OSAS) in relation to the data of a sleep study. Total 103 patients newly diagnosed with OSAS underwent overnight polysomnography and 24-hour ambulatory BP measurements. Patients without morning or nocturnal hypertension (control group), patients with morning hypertension but not nocturnal hypertension (surge-type group), and patients with both morning and nocturnal hypertension (sustained-type group) were compared. Morning hypertension was present in 54 patients (16 surge-type and 38 sustained-type). The apnea-hypopnea index and sleep efficiency were higher and lower, respectively, in the sustained-type group than in the other groups. Slow-wave sleep incidence was significantly lower in the sustained-type and surge-type groups than in the control group. These results suggest that approximately half the OSAS patients displayed morning hypertension, the sustained-type being more common than the surge-type. Poor sleep quality plays an important role in the pathogenesis of morning hypertension in both the sustained- and the surge-type group.

Age-related differences in the mechanism of nondipping among patients with obstructive sleep apnea syndrome.

The frequency of nondipper (those lacking the normal drop in nocturnal blood pressure [BP]) is high in patients with obstructive sleep apnea syndrome (OSAS). The objective of this study is to investigate age-related differences in the nocturnal BP profile of patients with OSAS. The study subjects included 214 patients with polysomnography-diagnosed OSAS. The status of dipper or nondipper was determined by 24-hour ambulatory BP measurements. We divided the subjects into three groups by age (younger, middle-aged, and elderly) and compared the frequency and sleep profiles of nondippers in the different age groups. The prevalence of nondippers was significantly higher in the elderly OSAS group than in the younger and middle-aged OSAS groups (69% vs. 45%, 47%; P < .05). In the younger OSAS group, nondippers, when compared with dippers, were characterized by higher apnea-hypopnea index (AHI, 48.2 ± 27.1 vs. 37.4 ± 23.0 times/h, P < .05), whereas in the middle-aged and elderly OSAS groups, the AHI of nondippers was almost identical to that of dippers. On the other hand, in the elderly OSAS group, nondippers, when compared with dippers, had shorter periods of slow wave sleep as measured by nonrapid eye movement stage 3-4, whereas nondippers and dippers in the other two age groups were not different in terms of slow wave sleep. These results indicate age-related differences in major mechanisms leading to nondipping. Severe apnea causes nondipping only in young OSAS patients, whereas disturbance of sleep quality plays a more important role in elderly OSAS patients.