Medline ® Abstracts for References 24-26

STUDY OBJECTIVE: To determine the impact of continuous positive airway pressure (CPAP) on weight change in persons with obstructive sleep apnea (OSA).

DESIGN SETTING AND PARTICIPANTS: The Apnea Positive Pressure Long-term Efficacy Study (APPLES) was a 6-month, randomized, double-blinded sham-controlled multicenter clinical trial conducted at 5 sites in the United States. Of 1,105 participants with an apnea hypopnea index≥10 events/ hour initially randomized, 812 had body weight measured at baseline and after 6 months of study.

INTERVENTION: CPAP or Sham CPAP.

MEASUREMENTS: Body weight, height, hours of CPAP or Sham CPAP use, Epworth Sleepiness Scale score.

RESULTS: Participants randomized to CPAP gained 0.35±5.01 kg, whereas those on Sham CPAP lost 0.70±4.03 kg (mean±SD, p = 0.001). Amount of weight gain with CPAP was related to hours of device adherence, with each hour per night of use predicting a 0.42 kg increase in weight. This association was not noted in the Sham CPAP group. CPAP participants who used their device≥4 h per night on≥70% of nights gained the most weight over 6 months in comparison to non-adherent CPAP participants (1.0±5.3 vs. -0.3±5.0 kg, p = 0.014).

CONCLUSIONS: OSA patients using CPAP may gain a modest amount of weight with the greatest weight gain found in those most compliant with CPAP.

COMMENTARY: A commentary on this article appears in this issue on page 995.

CITATION: Quan SF; Budhiraja R; Clarke DP; Goodwin JL; Gottlieb DJ; Nichols DA; Simon RD; Smith TW; Walsh JK; Kushida CA. Impact of treatment with continuous positive airway pressure (CPAP) on weight in obstructive sleep apnea.

STUDY OBJECTIVES: Obesity is an important risk factor for obstructive sleep apnea syndrome (OSAS), and weight loss can reduce apnea severity or even lead to resolution in some patients. Effective CPAP therapy may lead to weight loss by any of several proposed mechanisms, including, but not limited to, increased physical activity and increased responsiveness to leptin. This retrospective study sought to determine whether subjects who adhered to prescribed CPAP treatment for OSAS would lose weight, or gain less weight than control subjects who were either untreated or did not adhere to prescribed CPAP treatment.

METHODS: BMI was determined at the time of diagnosis and at followup approximately 1 year (10-14 months) later. Subjects who used CPAP>or = 4 h per night and>or = 70% of nights were considered treatment subjects. Control subjects used no treatment for OSAS or used CPAP<4 hours per night or<70% of nights for 1 year.

RESULTS: BMI of treatment and control subjects did not significantly differ (p = 0.3157). BMI increased with 1 year of CPAP use in women but not men (p = 0.0228) and in non-obese subjects (p = 0.0443). BMI did not significantly decrease in any group treated with CPAP.

CONCLUSIONS: CPAP was associated with weight gain in some; none lost weight. CPAP may affect weight in ways not measured here. Physicians should stress an active weight loss plan and not assume CPAP alone will lead to weight loss. A larger, prospective study may help clarify these findings.

BACKGROUND: Obstructive sleep apnea (OSA) is associated with obesity, insulin resistance (IR) and diabetes. Continuous positive airway pressure (CPAP) rapidly mitigates OSA in obese subjects but its metabolic effects are not well-characterized. We postulated that CPAP will decrease IR, ghrelin and resistin and increase adiponectin levels in this setting.

METHODS: In a pre- and post-treatment, within-subject design, insulin and appetite-regulating hormones were assayed in 20 obese subjects with OSA before and after 6 months of CPAP use. Primary outcome measures included glucose, insulin, and IR levels. Other measures included ghrelin, leptin, adiponectin and resistin levels. Body weight change were recorded and used to examine the relationship between glucose regulation and appetite-regulating hormones.

RESULTS: CPAP effectively improved hypoxia. However, subjects had increased insulin and IR. Fasting ghrelin decreased significantly while leptin, adiponectin and resistin remained unchanged. Forty percent of patients gained weight significantly. Changes in body weight directly correlated with changes in insulin and IR. Ghrelin changes inversely correlated with changes in IR but did not change as a function of weight.

CONCLUSIONS: Weight change rather than elimination of hypoxia modulated alterations in IR in obese patients with OSA during the first six months of CPAP therapy.