October - December 2008, Volume 4, Issue 4

Niculescu DA, Kohler W, Coculescu M

Continuous positive airway pressure treatment leads to weight gain in patients with obstructive sleep apnea syndrome

Acta Endo (Buc) 2008, 4 (4): 383-390
doi: 10.4183/aeb.2008.383

Obesity is an important risk factor for obstructive sleep apnea syndrome (OSAS). One would expect that effective treatment by continuous positive airway pressure (CPAP) would lead to weight loss due to decreased daytime sleepiness and improved physical activity. However, many papers suggest that shortage of sleep is a risk factor for obesity.\r\nAim. To assess the weight change after 1 year of effective CPAP treatment for OSAS.\r\nMethods. In this retrospective study OSAS was diagnosed in 109 subjects (50 women, 59 men; age 58?13 years). Eighty subjects used CPAP > 5 h per night in > 70% of nights and were considered treatment subjects. Twenty-nine subjects used CPAP < 5 hours per night or < 70% of nights and were considered control subjects. Patients were diagnosed using complete full-night or split-night polysomnography (70 and 39 patients respectively). Mean effective titrated CPAP pressure was 9.8 cm H2O. CPAP compliance was assessed through downloadable data from CPAP machine (19 patients) or clinical exam (90 patients). Body mass\r\nindex (BMI) was determined at the time of diagnosis and 1 year later (range 10-15 months).\r\nResults. Treatment and control subjects were similar regarding age, sex, BMI and apnea hypopnea index (AHI) at baseline. Weight increased in CPAP users (n=80) by 1.3 kg (CI 95% 0.4, 2.25; p<0.01) but not in control subjects (n=29) (mean difference in controls 0.37 kg, CI 95% -1.8, 2.5; p>0.05). BMI significantly increased in men (p<0.005), in subjects with severe OSAS (AHI>30 events/hour) (p<0.009) and in those younger than 65 years (p<0.01). Sleep architecture was investigated by full-night polysomnography in 50 regular CPAP users and 20 controls. In the subgroup of 18 treatment patients with lack of slow wave sleep (SWS) the increase in body weight was 2.6 kg (CI 95% 0.4, 4.9, p=0.02), more than double as compared with patients with SWS at baseline (n=32).\r\nConclusion. Effective CPAP treatment leads to a modest, but significant weight gain after 1 year in OSAS patients, especially in men with severe sleep apnea. This seems to be in relation to lack of SWS at baseline. An independent medical intervention for weight loss should be associated with CPAP treatment in sleep apnea syndrome.

Keywords: obstructive sleep apnea syndrome, CPAP, weight gain, BMI

Correspondence: William C. Kohler, MD, Florida Sleep Institute, 4075 Mariner Blvd, Spring Hill, FL 34609, USA. E-mail: kohler2@bellsouth.net