Occult nighttime hypertension in daytime normotensive older patients with obstructive sleep apnea

Abstract

Objectives: To assess nighttime blood pressure (BP), the dipping phenomenon and the relationships between nighttime BP, and polysomnography parameters in older patients with obstructive sleep apnea (OSA) who have been identified by their primary care physician as being normotensive during the daytime.

Design: Cross-sectional study.

Setting: University hospital-based geriatric sleep center.

Participants: Daytime normotensive, community-dwelling older adults, consecutively referred by their primary care physicians for suspicion of OSA.

Measurements: Overnight polysomnography and 24-hour ambulatory blood pressure measurement (ABPM). Daytime hypertension defined as systolic BP ≥135 mm Hg and/or diastolic BP ≥85 mm Hg. Nighttime hypertension defined as systolic BP ≥120 mm Hg and/or diastolic BP ≥70 mm Hg. Dipper pattern characterized by nighttime fall of mean BP ≥10%.

Results: Forty-five participants (30 OSA; 15 non-OSA) completed the study (76.9 ± 6.2 years old). ABPM indicated clinically significant nighttime systolic (132.5 ± 16.0) and diastolic (72.6 ± 9.4) hypertension in patients with OSA previously classified as daytime normotensives and found only a mild degree of nighttime systolic hypertension (123.7 ± 16.1) in patients without OSA (P = .105). A significant nondipping phenomenon was found in patients with OSA (-0.5 ± 7.4 vs 5.4 ± 6.4; P = .016). Nighttime mean BP (r = 0.301; P = .049) and dipping status (r = -0.478; P = .001) were correlated with apnea-hypopnea index. A significant correlation was found between systolic BP (r = 0.321; P = .035), diastolic BP (r = 0.373; P = .013), mean BP (r = 0.359; P = .018), and hypoxia (sleep time spend with SaO2 <90%).

Conclusion: Daytime normotensive older adults with OSA are at high risk for having occult nighttime hypertension. Thus, 24-hour ABPM may be appropriate for older patients with OSA whose clinical blood pressure does not display any daytime elevation.