Objective: To study the influence of obstructive sleep apnea (OSA) on 24-h BP.
Setting: Sleep laboratory of the Medical Department, Neukölln Hospital, Berlin, Germany.
Methods: In 93 subjects, noninvasive 24-h BP monitoring was performed with BP recordings made at 15-min intervals. Apnea severity was evaluated by means of a portable device that allows calculation of an oxygen desaturation index (ODI). A normal 24-h BP profile (dipping) was defined by a night/day BP ratio of 0.9.
Results: ODI was related to systolic and diastolic daytime (p<0.001) and nighttime BP (p<0.001) as well as systolic and diastolic BP night/day ratios (p<0.001). Multiple regression analysis showed that age and ODI were independently related to daytime BP. When subjects were grouped according to apnea severity, daytime BP increased as ODI increased: 127/80+/-10/11 mm Hg in habitual snorers (ODI 0 to 5), 135/87+/-15/9 mm Hg in mild OSA (ODI 6 to 30), and 140/90+/-13/10 mm Hg in severe OSA (ODI >30) (p values <0.05 for comparisons of OSA groups with habitual snorers). Compared to subjects with mild OSA or habitual snorers, BP night/day ratios were greater in patients with severe OSA (p values <0.05). Accordingly, hypertension and nondipping increased as ODI increased.
Conclusion: OSA is associated with hypertension independent of the confounding factors of age and obesity. Nondipping is related to apnea severity. These alterations might contribute to the increased mortality in patients with severe OSA.