Does medically induced weight loss improve obstructive sleep apnoea in the obese: review of randomized trials

Obstructive sleep apnoea is characterized by repeated periods of breathing cessation during sleep. Obstructive sleep apnoea is both common and underdiagnosed in the obese. A recent study found that as many as 86% of older obese type 2 diabetics had obstructive sleep apnoea. Obesity is independently associated with developing obstructive sleep apnoea, and the reverse may also occur. The prevalence of obstructive sleep apnoea is therefore expected to rise in the wake of the obesity epidemic. The number of partial (hypopnoea) or complete (apnoea) airway obstructions per hour (apnoea-hypopnoea index) is used to classify obstructive sleep apnoea as mild (5-14 events per hour), moderate (15-30) or severe (>30). Severe obstructive sleep apnoea is associated with a two to sixfold increase in all-cause mortality; the impact of mild and moderate obstructive sleep apnoea is less clear. Until recently, the evidence supporting a beneficial effect of weight loss on obstructive sleep apnoea has been limited by a lack of randomized trials. In 2009, at least three randomized controlled trials evaluated whether medically induced weight loss improves obstructive sleep apnoea. The treatment effect ranged from 42% to 62% improvement, although the highest estimate was seen in a very short duration study (9 weeks). Patients who either lost 10-15 kg or more, or had severe obstructive sleep apnoea at baseline, benefited most from treatment.