Active Voice: Weight Loss and Obstructive Sleep Apnea - What Lies Ahead?
By Devon A. Dobrosielski, Ph.D.
Viewpoints presented in SMB commentaries reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM.
Devon A. Dobrosielski, Ph.D., is an assistant professor of exercise science in the Department of Kinesiology at Towson University in Maryland. Dr. Dobrosielski is an ACSM member, focusing his research on examining the impact of exercise and sleep on the cardiovascular consequences of chronic disease. In particular, he is interested in determining whether exercise can serve as an effective countermeasure to vascular impairment commonly observed in the presence of sleep disorders.
This commentary presents Dr. Dobrosielskiís views on the topic of the research article which he and his colleagues published in the January 2015 issue of Medicine & Science in Sports & Exercise® (MSSE).
Weight loss is recommended by the American Academy of Sleep Medicine for all overweight adults with obstructive sleep apnea (OSA), a disorder associated with obesity and characterized by repeated episodes of upper airway obstruction, recurrent arousals and episodic oxygen desaturations during sleep. This recommendation has been bolstered in recent years by several large clinical trials that have demonstrated improvements in OSA severity with intensive lifestyle modification (e.g., dietary change and increased physical activity). These improvements are dose-dependent and are sustained once an intervention has ended or even when weight regain occurs.
Less well established is whether improvements in OSA severity, despite weight regain, translate into improved cardiovascular outcomes. OSA is linked to cardiovascular morbidity and mortality through a number of mechanisms that include endothelial dysfunction, inflammation and sympathetic activation. Moreover, abdominal obesity is an established risk factor for both OSA and cardiovascular disease.
Our most recent report, published in MSSE, is one of the first investigations to examine potential cardiovascular disease mechanisms in the context of an OSA intervention that reduces weight, alters body composition and increases fitness simultaneously. We found that after undergoing a 12-week intervention that included exercise and dietary-induced weight loss, older men and women with OSA had reduced disordered breathing events and showed improvements in nightly desaturations. These changes were accompanied by reductions in body fat and increased fitness. Uniquely, we also found that improved arterial distensibility (a marker of vessel wall damage) was related to improvement in the severity of nightly desaturations. These findings suggest that beneficial cardiovascular outcomes accrued through a lifestyle program may be influenced to a greater extent by OSA severity rather than body weight or composition. They also imply that vascular impairments existing in many patients with OSA may not be the cause or consequence of physical inactivity.We remain cautious in the interpretation of these data, but feel that testing the above hypotheses are important, especially since weight loss and increased physical activity are generally regarded as cornerstone therapies for reducing the burden of chronic diseases. Yet, clinicians and scientists also might want to consider the possible role that OSA may have in mediating the associations between reduced obesity and cardiovascular health. Indeed, there is evidence that OSA actually impairs weight loss. Moreover, while exercise is thought to confer cardioprotection through direct effects on endothelial function, this benefit may be lost, or at least attenuated, in the presence of undiagnosed OSA. Accordingly, screening for and treating OSA with continuous positive airway pressure might actually facilitate weight loss and allow for exercise to result in more beneficial cardioprotective outcomes. Clearly, there is much to be learned about long-term effects of lifestyle modification on cardiovascular health in OSA patients. The stage is set for continued research designed to explore the most effective treatment strategies for reducing OSA, with regard to weight loss and exercise programing. Addressing this would undoubtedly have major implications for reducing cardiovascular disease risk among obese patients with and without OSA.