From Medscape Medical News CME

Weight Loss Should Improve OSA in Obese Patients With Type 2 Diabetes CME

News Author: Laurie Barclay, MD
CME Author: Hien T. Nghiem, MD

October 6, 2009 — Weight loss should result in significant and clinically relevant improvements in obstructive sleep apnea (OSA) among obese patients with type 2 diabetes, according to the results of a multicenter randomized study published in the September 28 issue of the Archives of Internal Medicine.

"The belief that weight loss improves…OSA has limited empirical support," write Gary D. Foster, PhD, from the Center for Obesity Research and Education, Temple University in Philadelphia, Pennsylvania, and colleagues from the Sleep AHEAD Research Group of the Look AHEAD Research Group. "The purpose of this 4-center study was to assess the effects of weight loss on OSA over a 1-year period."

The study sample consisted of 264 participants with type 2 diabetes who were randomly assigned to either an intensive lifestyle intervention (behavioral weight loss program developed specifically for obese patients with type 2 diabetes) or to a diabetes support and education group (3 group sessions discussing effective diabetes management). Mean age was 61.2 ± 6.5 years, mean weight was 102.4 ± 18.3 kg, mean body mass index (calculated as weight in kilograms divided by height in meters squared) was 36.7 ± 5.7 kg/m², and mean apnea-hypopnea index (AHI) was 23.2 ± 16.5 events per hour.

Compared with participants in the support and education group, participants in the intensive lifestyle group lost more weight at 1 year (10.8 kg vs 0.6 kg; P < .001) and had a relative adjusted decrease in AHI of 9.7 ± 2.0 events per hour (P < .001). Total remission of OSA at 1 year occurred in more than 3 times as many participants in the intensive lifestyle group vs the support and education group, and the prevalence of severe OSA in the intensive lifestyle group was half that in the support and education group. The factors most predictive of changes in AHI at 1 year were initial AHI and weight loss (P < .01), with the greatest reductions in AHI occurring in participants with weight loss of at least 10 kg.

"Physicians and their patients can expect that weight loss will result in significant and clinically relevant improvements in OSA among obese patients with type 2 diabetes," the study authors write. "The greatest benefit was observed in men, in participants with more severe OSA at baseline, and in participants who lost the most weight."

Limitations of this study include lack of generalizability to younger patients, to patients without type 2 diabetes, or to patients with milder degrees of OSA. In addition, future research should address the mechanical, metabolic, and hormonal mechanisms underlying these improvements in OSA.

"The significant increase in AHI over 1 year in participants who were weight stable suggests that OSA is a rapidly progressing syndrome that will worsen without treatment in middle-aged obese adults with type 2 diabetes," the study authors conclude.

The National Institutes of Health (NIH) National Heart, Lung, and Blood Institute supported Sleep AHEAD. The NIH National Institute of Diabetes and Digestive and Kidney Diseases supported Look AHEAD. One of the study authors (Dr. Sanders) has disclosed various financial relationships with Philips-Respironics, Cephalon, and Sanofi-Aventis.

Arch Intern Med. 2009;169:1619-1626. Abstract

Clinical Context

Weight loss is frequently recommended to improve OSA in obese patients; however, this recommendation has limited empiric support. Existing studies evaluating the effects of weight loss in patients with OSA are limited by the small sample size (N = 8 – 26 participants), short duration (≤ 6 months), predominantly male samples (90%), and lack of patients in comparison groups who do not lose weight. More data are needed to help understand the expected benefits of weight loss in the management of OSA.

The purpose of this 4-center study was to assess the effects of weight loss on OSA in obese patients with type 2 diabetes during a 1-year period.

Study Highlights

• This randomized controlled study included 264 participants with type 2 diabetes and a mean (SD) age of 61.2 (6.5) years, weight of 102.4 (18.3) kg, body mass index of 36.7 (5.7) kg/m², and an AHI of 23.2 (16.5) events per hour.
• As part of the Look AHEAD study, the participants were randomly assigned to either a behavioral weight loss program developed specifically for obese patients with type 2 diabetes (intensive lifestyle intervention) or 3 group sessions related to effective diabetes management (diabetes support and education).
• Patients were excluded if they had previous surgical or current medical treatments of OSA.
• The intensive lifestyle participants were prescribed portion-controlled diets, with prescribed energy intake of 1200 to 1500 kcal/day if the patients weighed less than 113.6 kg or 1500 to 1800 kcal/day if the patients weighed 113.6 kg or more, with 30% less calories from fat. The recommended physical activity was 175 minutes per week of moderate-intensity activity.
• The support and education participants attended group sessions focused on diet, physical activity, and social support for effective diabetes management.
• Of the 264 study participants, 38.7% had mild OSA, 35.2% had moderate OSA, and 26.1% had severe OSA.
• Results demonstrated that the intensive lifestyle participants lost more weight at 1 year vs the support and education participants (10.8 kg vs 0.6 kg; P < .001). They also experienced greater reductions in waist and neck circumferences vs the support and education participants.
• Overall, OSA among the intensive lifestyle participants improved, whereas OSA worsened among the support and education participants.
• Among the intensive lifestyle participants, the AHI decreased from 22.9 (18.0) to 18.3 (15.3) (P < .001 within the group), whereas among the support and education participants, the AHI increased from 23.5 (15.0) to 28.3 (20.7) (P < .01 within the group).
• Relative to the support and education group, the intensive lifestyle intervention was associated with an adjusted (SE) decrease in AHI of 9.7 (2.0) events per hour (P < .001).
• At 1 year, more than 3 times as many participants in the intensive lifestyle group vs the support and education group had total remission of their OSA, and the prevalence of severe OSA among intensive lifestyle participants was half that of the support and education group.
• More than twice as many intensive lifestyle participants vs the support and education participants demonstrated improvement in their OSA category (eg, severe to moderate, moderate to mild, and mild to none) at 1 year.
• There were significant treatment interactions with both sex (P < .02) and baseline AHI (P < .001). Intensive lifestyle was more effective in reducing the AHI in men vs women and was more effective in participants with higher levels of baseline AHI vs those with lower levels of baseline AHI.
• Initial AHI and weight loss were the strongest predictors of changes in AHI at 1 year (P < .01).
• Participants with a weight loss of 10 kg or more had the greatest reductions in AHI, specifically 11.3 events per hour.
• Limitations of this study were that the results were not generalizable to younger patients, to patients without type 2 diabetes, or to patients with milder degrees of OSA.

Clinical Implications

• Current studies evaluating the effects of weight loss in patients with OSA are limited by the small sample size, short duration, predominantly male samples, and lack of patients in the comparison groups who do not lose weight.
• Weight loss will result in significant and clinically relevant improvements in OSA among obese patients with type 2 diabetes.

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