Obesity and obstructive sleep apnea (OSA) tend to co-exist and are associated with high blood pressure. The effects of weight loss and continuous positive airway pressure (CPAP), the standard therapy for OSA, on blood pressure have been previously studied individually, but the incremental benefit of combination therapy (weight loss and CPAP therapy) over either therapy alone in obese patients with OSA has been unknown. Now, new research from a multidisciplinary team at the Perelman School of Medicine at the University of Pennsylvania has shown that the combination of these two therapies for patients with OSA can help lower blood pressure. The study results were reported today at the 62nd Annual Scientific Session of the American College of Cardiology in San Francisco (Abstract # 918-6).
"Obstructive sleep apnea is present in a significant proportion of U.S. adults, putting them at an increased risk for high blood pressure and heart disease. We need to find optimal ways to help these patient reduce their risk and improve their cardiovascular health," said lead study author Julio Chirinos, MD,PhD, assistant professor of Medicine. "This is the first study that addresses the incremental benefit of combining two previously identified strategies (weight loss and therapy for OSA with CPAP) over either therapy alone. We found that the combination of weight loss and CPAP therapy is a better strategy to reduce blood pressure than either therapy alone."
In the current study, the authors screened 544 subjects in order to identify subjects with obesity, moderate-to-severe obstructive sleep apnea (diagnosed using an overnight study in a sleep laboratory) and high levels of C-reactive protein (an inflammatory marker associated with heart disease). They randomized 181 subjects meeting inclusion criteria for the trial to one of three arms, for 24 weeks: (1) CPAP therapy; (2) a weight loss intervention (involving a dietary and lifestyle intervention), or; (3) a combination of the two interventions.
To measure differences in blood pressure across the groups, the research team measured brachial systolic blood pressure and brachial pulse pressure in each group. In a subset of subjects, the authors also measured central (aortic) arterial pressure using arterial tonometry. The authors analyzed the changes in blood pressure in all subjects randomized (intent-to-treat analyses). They also performed pre-specified analyses including only subjects that met minimal compliance criteria for the CPAP and weight loss intervention.
As expected, subjects randomized to CPAP alone did not experience weight loss, whereas subjects randomized to weight loss or combination therapy experienced a significant reduction in body weight and body mass index. In intent-to-treat analyses, after 24 weeks of therapy, reductions in brachial systolic pressure were observed in all 3 groups, whereas the reduction in brachial pulse pressure reached statistical significance only in the combination therapy arm. Among compliant subjects, the reduction in brachial systolic blood pressure was significantly larger in the combination therapy arm (14.1 mmHg) compared to either CPAP alone (3 mmHg) or weight loss alone (6.8 mmHg). An additional interesting finding of the study was that CPAP induced a reduction in central pulse pressure, which was not evident from brachial pulse pressure measurements.
"These findings have important implications for cardiovascular risk reduction in this population," said Chirinos. "Therefore, more emphasis should be placed on not only addressing the sleep apnea, but also treating the obesity in this patient population. It is also an important goal to find better ways to enhance compliance with CPAP therapy and weight loss interventions in these patients."
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