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ABSTRACT & COMMENTARY
By Barbara A. Phillips, MD, MSPH
Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington
Dr. Phillips serves on the speakers bureau for PotomaCME.
SOURCE: Chirinos JA, et al. CPAP, weight loss, or both for obstructive sleep apnea. N Eng J Med 2014;370:2265-2275.
SYNOPSIS: The combination of CPAP and weight loss improves blood pressure better than either treatment alone.
Because weight loss is beneficial for obese and overweight patients with obstructive sleep apnea (OSA), these investigators evaluated the effects of weight loss and continuous positive airway pressure (CPAP), singly and in combination, on clinical outcomes of OSA. To do this, they enrolled obese adults with moderate-to-severe OSA and a serum level of C-reactive protein (CRP) of at least 1.0 mg/L. Patients were randomized to either weight loss alone, CPAP alone, or CPAP and weight loss together. In the CPAP and CPAP plus weight loss groups, objective adherence to CPAP therapy was monitored. Participants in the weight loss and CPAP plus weight loss groups had individual weekly counseling sessions with specific caloric targets and initial dietary composition based on National Cholesterol Education Program (NCEP), with a more structured diet (including two to three liquid meal replacements/day after week 2), unsupervised exercise, and cognitive-behavioral treatment.
Assessments were performed at baseline, 8, and 24 weeks. Outcome measures included CRP, lipoproteins, insulin sensitivity, and blood pressure. The authors analyzed results both based on intention-to-treat and based on per protocol (achieving targets) outcomes. Per protocol targets were at least a 5% loss of baseline weight and CPAP adherence of at least 4 hours a night for 70% of nights. Because of the two ways of looking at the outcomes (what the patients actually did, in terms of weight loss and CPAP use, in contrast to what they were randomized to be doing), the results of this study are a bit complicated to sort out. In general, this discussion will focus on the per protocol analyses (those patients who actually met the targets of weight loss and/or CPAP use).
Of 181 patients initially enrolled, 136 completed the full 6 months of evaluation (a drop out rate of 1 in 4). For the patients who completed the study, the decline in body weight was similar in the weight loss and CPAP plus weight loss groups (about 15 pounds in each case). Those in the CPAP alone group did not lose weight. The average duration of CPAP use was 4 hours per night, with no significant differences between the CPAP and CPAP plus weight loss groups.
At the end of the study, CRP levels were significantly reduced in the weight loss and in the CPAP plus weight loss groups, but not in the CPAP alone group. Similarly, insulin sensitivity increased in the weight loss and CPAP plus weight loss groups, but not in the CPAP alone group. Similar findings were noted with changes in serum triglycerides and cholesterol levels, with greater reductions in patients assigned to weight loss (with or without CPAP) than in those the CPAP alone group. On the other hand, there was no significant change in HDL cholesterol levels in any of the study groups.
In the intention-to-treat analysis, systolic blood pressure was reduced in all three study groups with no significant between-group differences. In the per-protocol (targets met) population, the reduction in systolic blood pressure was greater in the combined-intervention group (14.1 mm Hg) than in the weight-loss group (6.8 mm Hg) or the CPAP group (3.0 mm Hg) and the reduction in mean arterial pressure was significantly greater in the CPAP plus weight loss group than in either the weight loss group or the CPAP group. In the per-protocol population, the reduction in pulse pressure was greater in the CPAP plus weight loss group and weight loss group than in the CPAP alone group.
In other words, in adults with obesity and OSA, CPAP combined with weight loss did not reduce CRP levels more than either intervention alone, but weight loss provided an additional improvement in insulin sensitivity and serum triglycerides when combined with CPAP. The combination of CPAP and weight loss caused significantly greater reduction in blood pressure than either treatment alone.
With regard to adverse events, nasal or upper airway symptoms were reported in an equal number of participants in each group (including the weight loss alone group!).
This interventional study goes a long way in helping to sort out the relative benefits of CPAP and weight loss on cardiovascular risk factors in patients with both sleep apnea and obesity (which tend to overlap). Perhaps the strongest message is that, at least in the short (6 month) run, weight loss appears to confer at least as much cardiovascular risk reduction as does CPAP. A couple of caveats are in order, though. The first is that the combination of CPAP and weight loss resulted in significantly greater reduction in blood pressure than either CPAP or weight loss alone. The second important footnote is that weight loss really did occur in patients randomized to a weight loss intervention in this study, probably because the weight loss intervention was intense, structured, and labor-intensive. In real life, this is much less likely to occur. Indeed, it’s now pretty clear that CPAP does not facilitate weight loss, and probably even promotes weight gain.1 Indeed, the patients randomized to CPAP alone in this study did not lose weight.
So, if we really want to optimize cardiovascular risk reduction in obese patients with sleep apnea, simply slapping on a CPAP mask is not enough. Specific, focused efforts at weight loss are essential. Not many of us have a mechanism to provide the kind of weight loss program that was used in this study. To quote the Methods section: "Dietary composition was aligned with recommendations from the National Cholesterol Education Program (NCEP). Self-selected foods within the framework of the NCEP diet were prescribed for the first 2 weeks. For weeks 3 to 19, a more structured diet was prescribed, including two to three liquid meal replacements per day. Unsupervised exercise was initiated at week 4, starting with four 15-minute weekly sessions that increased progressively to four 50-minute weekly sessions by week Cognitive-behavioral strategies, including self-monitoring, goal setting, stimulus control, problem solving and relapse prevention, were used to facilitate and maintain weight loss." Not only is such a program difficult to organize, getting it paid for is virtually impossible. Further, my educated guess is that it was this intensive weight loss program, rather than any other aspect of this project, that resulted in the loss of about one-fourth of the research participants in this study.
So what’s a clinician to do? This report strengthens the evidence that we are failing our obese patients if we don’t address weight loss in some way. But maybe it doesn’t have to be quite so complicated. Recent reports2,3 indicate that commercial programs are at least as effective (and much more accessible) to real-world patients than intensive clinic-based programs. A specific referral for a commercial weight loss program is an option to consider.