NEW ORLEANS – Contrary to previously published data suggesting continuous positive airway pressure (CPAP) produces weight gain in patients with obstructive sleep apnea (OSA), new study findings presented at the annual meeting of the Endocrine Society provided data supporting the exact opposite conclusion.
“We think the data are strong enough to conclude that combining CPAP with a weight-loss program should be considered for all OSA patients. The weight-loss advantage is substantial,” reported, of the University of Arkansas for Medical Sciences, Little Rock.
Both weight loss and CPAP have been shown to be effective for the treatment of OSA, but concern that CPAP produces a counterproductive gain in weight was raised by findings in a meta-analysis in which CPAP was associated with increased body mass index (). As a result of that finding, some guidelines subsequently advised intensifying a weight-loss program at the time that CPAP is initiated to mitigate the weight gain effect, according to Dr. Mao. However, he noted that prospective data were never collected, so a causal relationship was never proven. Now, his data support the opposite conclusion.
In the more recent study, 300 patients who had participated in an intensive weight-loss program at his institution were divided into three groups: OSA patients who had been treated with CPAP, symptomatic OSA patients who had not been treated with CPAP, and asymptomatic OSA patients not treated with CPAP. They were compared retrospectively for weight change over a 16-week period.
“This was a very simple study,” said Dr. Mao, who explained that several exclusions, such as thyroid dysfunction, active infection, and uncontrolled diabetes, were used to reduce variables that might also affect weight change. At the end of 16 weeks, the median absolute weight loss in the CPAP group was 26.7 lb (12.1 kg), compared with 21 lb (9.5 kg) for the symptomatic OSA group and 19.2 lb (8.7 kg) for the asymptomatic OSA group. The weight loss was significantly greater for the CPAP group (P less than .01), compared with either of the other two groups, but not significantly different between the groups that were not treated with CPAP.
“The differences remained significant after adjusting for baseline BMI [body mass index], age, and gender,” Dr. Mao reported.
Asked why his data contradicted the previously reported data, Dr. Mao said that the previous studies were not evaluating CPAP in the context of a weight-loss program. He contends that when CPAP is combined with a rigorous weight-reduction regimen, there is an additive benefit from CPAP.
According to Dr. Mao, these data bring the value of CPAP for weight loss full circle. Before publication of the 2015 meta-analysis, it was widely assumed that CPAP helped with weight loss based on the expectation that better sleep quality would increase daytime activity. However, in the absence of strong data confirming that effect, Dr. Mao believes the unexpected results of the 2015 study easily pushed the pendulum in the opposite direction.
“The conclusion that CPAP increases weight was drawn from studies not designed to evaluate a weight-loss effect in those participating in a weight-loss program,” Dr. Mao explained. His study suggests that it is this combination that is important. He believes the observed effect from better sleep quality associated with CPAP is not necessarily related to better daytime function alone.
“Patients who sleep well also have more favorable diurnal changes in factors that might be important to weight change, such as leptin resistance and hormonal secretion,” he said. Although more work is needed to determine whether these purported mechanisms are important, he thinks his study has an immediate clinical message.
“Patients with OSA who are prescribed weight loss should also be considered for CPAP for the goal of weight loss,” Dr. Mao said. “We think this therapy should be started right away.”
SOURCE: Mao Y et al. ENDO 2019, Session.