• Sally Middleton, Walter Vermeulen, Karen Byth, Colin E Sullivan, and Peter G Middleton.
• David Read Laboratory, Department of Medicine, University of Sydney, Sydney, Australia.
• Respirology. 2009 Apr 1; 14 (3): 404-10.

Background And ObjectiveWhile recent meta-analyses suggest that OSA elevates daytime blood pressure (BP), most studies have included patients with mild hypertension, so CPAP treatment has only reduced BP by 2-3 mm Hg. To determine the strength of the OSA-BP relationship, this study examined the effect of CPAP in a cohort where severe OSA and under-treated hypertension coexist.MethodsBaseline demographic and sleep study data were recorded in 221 consecutive patients referred for sleep studies in Samoa. OSA was treated with CPAP and BP recorded for 6-7 months in 180 patients. A subgroup of 64 patients, representative of the entire group, but with regular follow-up, is also described.ResultsOSA was diagnosed in 218/221 patients; of those who commenced CPAP, 180 returned for follow-up at least once within 7 months. Following CPAP, BP decreased by 7.1/5.9 mm Hg at 1 month and 12.9/10.5 mm Hg at 6 months (n = 180, P < 0.0001). In the 64 patients with regular follow-up, those with the highest baseline BP had the greatest fall in BP with CPAP; BP in the hypertensive subgroup (32/64) decreased 21.5/13.1 mm Hg at 6 months (P < 0.0001).ConclusionsHypertensive OSA patients can exhibit large falls in BP with CPAP at 1 month, with further significant reductions at 3 and 6 months. Overall, the fall in BP was proportional to the initial elevation of the BP with many patients achieving normal BP at 6 months.

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