Weight gain induced by continuous positive airway pressure in patients with obstructive sleep apnea is mediated by fluid accumulation: a randomized crossover controlled trial

Abstract

Recent studies have shown that the treatment of obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) is associated with weight gain over periods ranging from 3 to 6 months (1–4). However, the mechanisms are conflicting and include reduction in basal metabolic rate (BMR) because of the resolution of OSA (4) and increase in caloric intake (4), leading to increase in fat (4) and lean body mass (3, 4).

Fluid accumulation is a well-known effect of positive pressure ventilation (5). The reversal of OSA-associated nocturia during CPAP (6) is an additional potential mechanism of fluid accumulation. We hypothesized that CPAP induces weight gain within 1 week of the same order of magnitude of previous longer studies and is explained by fluid accumulation. We used the CPAP withdrawal paradigm and only recruited patients with high CPAP adherence (7). The short-term protocol reduces the impact of confounding factors, including increase in fat and muscle mass previously reported (3, 4).