Weight loss, CPAP may reduce CV risk factor burden in obese patients with sleep apnea

In patients with obstructive sleep apnea, weight loss was associated with reduced C-reactive protein and continuous positive airway pressure was associated with reduced BP, according to two studies published in The New England Journal of Medicine.

In one study, researchers found that adults with obesity and obstructive sleep apnea had reduced C-reactive protein (CRP) levels when assigned to a weight-loss intervention with or without continuous positive airway pressure (CPAP), but levels did not decrease with CPAP alone.

In the other study, patients with CVD or multiple CV risk factors and obstructive sleep apnea assigned to CPAP demonstrated a reduction in BP.

Obesity and CRP

Julio A. Chirinos, MD, PhD, from the University of Pennsylvania and Philadelphia Veterans Affairs Medical Center, studied 181 obese patients with moderate-to-severe obstructive sleep apnea and CRP levels >1 mg/L. The patients were assigned CPAP, a weight-loss intervention or a combination of both for 24 weeks to assess the effect of the combined intervention compared with CPAP or weight loss alone. The primary outcome was change in CRP level. Secondary outcomes included changes in insulin sensitivity, atherogenic dyslipidemia and BP.

For 146 patients who completed at least one follow-up assessment, those assigned to the weight-loss intervention and the combined intervention had significant reductions in CRP level (P<.001 for both), insulin sensitivity index (combined group, P<.001; weight-loss group, P=.01) and serum triglycerides (combined group, P<.001; weight-loss group, P=.03).

However, the changes in CRP, insulin and triglycerides were not observed in the group assigned CPAP alone.

Systolic BP was reduced in all three groups, according to the researchers. There was no difference in reduction among in the intention-to-treat population, but in a per-protocol analysis of 90 patients who met prespecified criteria for adherence, those assigned the combined intervention had a larger reduction in systolic BP compared with those assigned weight loss alone (P=.02) or CPAP alone (P<.001).

“These data argue against an independent causal relationship between obstructive sleep apnea and these [CV] risk factors in this population, and suggest that CPAP is not an effective therapy to reduce the burden of these particular risk factors,” Chirinos said in a press release. “These findings also indicate that weight-loss therapy should be a central component of strategies to improve the [CV] risk factor profile of obese patients with [obstructive sleep apnea]. The design of this trial allowed us to conclude that both obesity and sleep apnea are causally related to high [BP].”

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CVD and BP

Daniel J. Gottlieb, MD, MPH, and colleagues conducted and randomized controlled trial of patients with CVD or multiple CV risk factors to evaluate the effects of nocturnal supplemental oxygen and CPAP on CV risk markers. The primary outcome was 24-hour mean arterial pressure at 12 weeks.

The 318 participants, all of whom had an apnea-hypopnea index of 15 to 50 events per hour, were randomly assigned to education on sleep hygiene and healthy lifestyle, education plus CPAP, or education plus nocturnal supplemental oxygen.

At 12 weeks, 281 participants could be evaluated for ambulatory BP. Mean arterial pressure at 12 weeks was lower in the CPAP group than the control group (–2.4 mm Hg; 95% CI, –4.7 to –0.1; P=.04) or the oxygen group (–2.8 mm Hg; 95% CI, –5.1 to –0.5; P=.02).

The researchers found no difference in mean arterial pressure between the oxygen group and the control group.

“This study offers no support for the common but largely untested clinical practice of providing supplemental oxygen as salvage therapy in patients with obstructive sleep apnea for whom CPAP is problematic,” Gottlieb, director of the Sleep Disorders Center at Veterans Affairs Boston Healthcare System, and colleagues wrote.

In a related editorial, Robert C. Basner, MD, from the Columbia University College of Physicians and Surgeons, wrote that both studies had design limitations that “limit the interpretation of the explicit findings” but they yielded important treatment considerations for people with obstructive sleep apnea.

For more information:

Basner RC. New Engl J Med. 2014;370:2339-2341.

Chirinos JA. New Engl J Med. 2014;370:2265-2275.

Gottlieb DJ. New Engl J Med. 2014;370:2276-2285.

Disclosure: Both studies were funded by the NHLBI. See the full studies for a list of the researchers’ relevant financial disclosures. Basner served on the data and safety monitoring board for the study conducted by Chirinos and colleagues.