CPAP, Weight Loss, or Both for Obstructive Sleep Apnea
Does continuous positive airway pressure (CPAP), combined with weight loss, reduce a systemic marker of inflammation in a population of obese patients with obstructive sleep apnea (OSA)?
This was a randomized, parallel group 6-month trial of obese (body mass index [BMI] >30 kg/m2) nondiabetic patients with moderate to severe OSA (apnea-hypopnea index >15). Patients were excluded for fasting glucose >125 mg/dl, abnormal depression screening survey (Beck), C-reactive protein (CRP) <1.0, baseline blood pressure >160/95 mm Hg, and safety reasons (driving risk). Randomization was conducted according to age, sex, and statin use. Dietary intervention was based on weight and was aligned with the National Cholesterol Education Program. Adherence to CPAP was done via wireless monitoring for an average of 4 hours/night at least 70% of the total number of nights. The primary endpoint was reduction in CRP. Secondary endpoints were insulin sensitivity, cholesterol levels, and blood pressure.
A total of 544 patients were screened, and 181 were randomized. A total of 136 completed the study (25% attrition rate). There were 61, 58, and 62 patients in the weight loss, CPAP, and combined treatment arms, respectively. Approximately 50-60% of subjects were white men averaging 48-50 years old. There was no significant difference in baseline characteristics, including a 20% statin use. No serious adverse events occurred. After applying prespecified adherence criteria at 6 months, only 27, 39, and 24 (weight loss, CPAP, and combined treatment arms) patients were in the final analysis. Both groups with a weight loss arm lost an average of 7 kg. Patients randomized to weight loss only and those assigned to the combined interventions had reductions in CRP levels, insulin resistance, and serum triglyceride levels. None of these changes were observed in the group receiving CPAP alone. Blood pressure was reduced in all groups. The combined interventions resulted in a larger reduction in systolic blood pressure and mean arterial pressure than did either CPAP or weight loss alone.
The authors concluded that weight loss combined with CPAP did not have an incremental effect on CRP levels compared to either treatment alone. However, CPAP combined with weight loss did result in a larger reduction in blood pressure readings at 6 months compared to either treatment alone.
Weight loss is an effective strategy to reduce both cardiovascular risk in the general population and apnea-hypopnea index in patients with OSA. What is new in the current study, however, is that weight loss reduced cardiovascular risk (CRP levels) in obese patients with OSA. This is yet another trial to show a benefit of an intervention in OSA, even in the absence of subjective sleepiness. However, to determine further pathogenic interactions of heart disease and OSA will require larger and longer studies.
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