Continuous positive airway pressure (CPAP) may be only modestly effective for ameliorating metabolic syndrome in patients with moderate to severe obstructive sleep apnea (OSA).
That conclusion comes from investigators in a randomized controlled, trial, who found that, among 100 patients with OSA and a recent diagnosis of metabolic syndrome (MS), 18% of those assigned to use CPAP at night had a reversal of MS at 6 months of follow-up, compared with 4% of controls who were assigned to use nasal strips at night (P = .04).
The majority of patients assigned to CPAP still retained their MS diagnoses at 6 months, and CPAP did not significantly reduce individual components of the syndrome. Use of CPAP was, however, associated with small reductions in visceral fat and improvement in endothelial function, reported Sara Q.C. Giampa, PhD, from the University of São Paulo, and colleagues.
“Despite a significant rate of MS reversibility after CPAP therapy, most of the patients maintained the MS diagnosis. The modest effects of CPAP on MS reversibility underscore the need for combined therapy with CPAP, aiming to maximize metabolic syndrome recovery in parallel with improvements in OSA severity and related symptoms,” according to their study, reported in the journal CHEST®.
Asked whether he still recommends CPAP to patients with OSA and the metabolic syndrome, given the findings, corresponding author Luciano F. Drager, MD, PhD, replied “yes, definitely.”
“Despite the modest rate in reversing metabolic syndrome after CPAP, the rate was 5-fold higher than non-effective treatment (18% vs. 4%),” he said in an interview.
Dr. Drager noted that studies of other single interventions such as physical exercise to reverse MS in patients with OSA also had modest results.
A researcher who studies the relationship between sleep, circadian rhythms, and metabolism commented that, although the patients in the CPAP group were compliant with the assigned equipment and had both reductions in apneic events and improvement in oxygen saturation, the effect of CPAP on the metabolic syndrome was rather small.
“The CPAP was doing what we thought it was supposed to do, but it didn’t have the magnitude of effect on the metabolic syndrome as I expected or I think as the authors expected,” said Deanna Arble, PhD, assistant professor of biological science at Marquette University, Milwaukee.
She noted that the study also failed to detect a significant improvement in the blood pressure component of metabolic syndrome.
“In my experience and my review of the literature, blood pressure tends to be the one that’s improved most dramatically with CPAP,” she said.
Dr. Arble was not involved in the study.
Study details
In the trial, titled TREATOSA-MS, the investigators enrolled 100 patients with a recent diagnosis of metabolic syndrome and moderate to severe OSA, defined as 15 or more apnea-hypopnea index events per hour. The patients were stratified by body mass index and then randomized to undergo therapeutic CPAP or to use nasal strips for 6 months.
At baseline and at the end of each intervention investigators measured anthropometric variables, blood pressure, glucose, and lipid profiles. They also leptin and adiponectin, body composition, food intake, physical activity, subcutaneous and abdominal fat (visceral and hepatic), and endothelial function to control for potential confounders.
As noted previously, they found that after 6 months “most patients with OSA randomized to CPAP retained the MS diagnosis, but the rate of MS reversibility was higher than observed in the placebo group.” The difference in metabolic syndrome reversal, 18% with CPAP versus 4% with nasal strips, translated into a hazard ratio favoring CPAP of 5.27 (P = .04).
Also as noted, in analyses adjusted for baseline values, CPAP did not significantly improve either weight, liver fat, lip profiles, or the adiposity biomarkers leptin and adiponectin, but did have “very modest” influence on reducing visceral fat and improving endothelial function.
Rigorous study
Dr. Arble said that most studies of the association between OSA and metabolic syndrome have focused on only one or two of the parameters that were included in the TREATOSA-MS study, giving the findings additional weight.
“This could potentially be a very good, carefully controlled first insight into how obstructive sleep apnea is related to the metabolic syndrome,” she said.
The study was funded by grants Fundação de Amparo Q22 à Pesquisa do Estado de São Paulo and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior. The authors and Dr. Arble reported having no conflicts of interest to disclose.