Two months of mandibular-advancement therapy significantly reduced the severity of obstructive sleep apnea (OSA) in patients with severe OSA, but had no effect on inflammatory and metabolic biomarkers, a new study from France shows.

Systemic inflammation and metabolic disorders are among the intermediary mechanisms connecting OSA with cardiovascular disease (CVD), Dr. Frederic Gagnadoux of CHU d'Angers and colleagues note in Thorax, online.

Mandibular-advancement devices (MAD) have emerged as the primary therapeutic alternative to continuous positive airway pressure (CPAP) for OSA. Although CPAP is superior at reducing OSA severity, "most trials comparing MAD and CPAP have reported similar health outcomes," the authors point out.

Inflammatory biomarkers

However, after adjustment for baseline value, age, gender, BMI and baseline AHI, no significant differences were found between the two groups in terms of metabolic or inflammatory biomarkers, including C-reactive protein interleukin-6, tumor necrosis factor-alpha (TNF-a), leptin, adiponectin and others. The sole exception was in the male population, where a significant decrease in TNF-a receptor 1 levels was noted in the effective-MAD group.

Dr. Vsevolod Y. Polotsky, director of Sleep Basic Research at Johns Hopkins University School of Medicine, in Baltimore, Maryland, told, "The goal is to effectively treat sleep apnea to reduce the cardiovascular and metabolic risk. It has not been achieved so far because the patients poorly comply with CPAP therapy, and MAD is not effective to control OSA in many patients."

Sleep apnea

"The current literature suggests that even partial improvement of sleep apnea . . . may be enough to alleviate sleepiness and snoring; complete resolution of apnea may be required to subdue inflammation," he added.

Dr. Polotsky pointed to a study published in 2015, in which patients were admitted to a lab for eight hours of CPAP nightly for two weeks. This approach resulted in improvement in insulin resistance and glucose tolerance, a result not seen in other studies, when patients used CPAP less consistently.

"The bottom line is we will not know if OSA therapy is effective in abolishing the cardiovascular risk unless we are able to treat patients effectively (like well-titrated CPAP) with the therapy they can tolerate/adhere to (like MAD)," Polotsky concluded.

Dr. Nancy Collop, director of the Emory Sleep Center at Emory University, in Atlanta, told Reuters Health that she had some issues with the study, including the fact that nearly a third of the participants dropped out and the two-month time frame. "It may take longer to show an improvement," she said.

"The most common problem with CPAP is that people may not use it enough, either all night or some nights not at all. Most studies do show more benefit with more use," Dr. Collop said.

CPAP over MAD

"Another benefit of CPAP over MAD that is often not commented on," she added, "is that CPAP improves oxygenation beyond its effect on keeping the airway open, because it expands the lungs more and they pick up more oxygen."