Losing weight in moderate to severe obstructive sleep apnoea

Given that obesity is the only major modifiable risk factor for obstructive sleep apnoea, it may seem superfluous to perform a randomised controlled trial of an intervention to reduce weight.1 Indeed, a recent Cochrane review looking at weight loss in this disorder found no relevant randomised controlled trials.2

This has been a major gap in the evidence based treatment of sleep apnoea. In the linked randomised controlled trial (doi:10.1136/bmj.b4609), Johansson and colleagues assess whether weight loss due to a very low energy diet reduces moderate and severe obstructive sleep apnoea in obese men who were all using continuous positive airway pressure.3

Research has emphasised mechanical interventions for obstructive sleep apnoea, such as nasal continuous positive airway pressure or mandibular advancement splints. Mechanical treatments may be efficacious in that they limit the condition when used, but they are less effective over the medium to long term,4 possibly because of difficulties with adherence.5 Pharmacotherapy and upper airway surgery have not provided a cure.

Research into weight loss for obstructive sleep apnoea has also been limited by the lack of clinical equipoise. Partly this is because reducing obesity seems such an obvious aim, yet the long term effectiveness of weight loss as a sole treatment for this condition is unknown. We have little robust data about how people with obstructive sleep apnoea can lose weight, keep the weight off, or even what effect it will have.

A recent randomised controlled trial from Finland of diet induced weight loss for mild obstructive sleep apnoea reported positive results.6 It compared a 12 week very low calorie diet and supervised lifestyle counselling programme with a single general dietary and exercise counselling session in 72 adults with mild obstructive sleep apnoea (apnoea-hypopnoea index (AHI) 5-15 events each hour of sleep) and body mass index (BMI) 28-40. The 3.5 unit decrease in BMI after one year induced by the lifestyle modification programme was associated with a significant 63% remission of obstructive sleep apnoea compared with 35% remission in controls. However, the clinical importance of mild obstructive sleep apnoea is still unclear because it has yet to be conclusively linked with morbid outcomes.

In contrast, moderate-severe obstructive sleep apnoea (AHI 15+ and 30+) in middle aged people is associated with an increased risk of mortality.7 8 9 Given this risk, and the poor tolerance of standard treatment, we urgently need to know what can be achieved with weight loss. Johansson and colleagues provide the first high quality evidence that moderate-severe obstructive sleep apnoea can be treated with weight loss. In a nine week, open label, randomised controlled trial they tested a liquid, very low energy, diet combined with lifestyle counselling and compared it with weight maintenance in 63 obese men (BMI 30-40) with at least moderate obstructive sleep apnoea who were all using continuous positive airway pressure (mean AHI 37, SD 15; range 15-77). Weight loss in the intervention group was significantly greater than in the control group (−5.7 kg/m², 1.1; −8.2 to −3.4 v 0.3, 0.6; −0.6 to 1.9). After nine weeks, mean AHI was 12 in the intervention group (7; 1-30) and 35 in the control group (14; 14-75). The authors concluded that weight loss reduced obstructive sleep apnoea to mild severity in 50% of patients and eradicated it in another 17%.

How does this new information help us manage obstructive sleep apnoea? Firstly, the trial shows that it is possible to help patients with this condition lose weight through lifestyle modification. Secondly, doing this has a good chance of reducing the severity of their disease below the level of harm. The obvious advantages of weight loss are the benefits on obesity related comorbidities. Standard device based treatment for obstructive sleep apnoea has not yet been shown to affect weight or improve comorbidies such as diabetes, although it has a mildly beneficial effect on blood pressure.4

The study has limitations. The trial was only nine weeks long, which leaves open the question of the long term sustainability of the weight loss. The method needs to be tested in women, in more and less obese patients, and in those unable to tolerate continuous positive airway pressure. Weight loss induced via bariatric surgery might, for example, be a better option in more obese patients.10 A remaining problem is that although weight loss improves obstructive sleep apnoea, in some patients the disorder persists despite weight loss.11 Currently it is unclear how to identify such non-responders, and follow-up evaluation remains vital in the execution of weight loss treatment.

Sleep apnoea is a multifactorial disease with several contributing pathophysiological processes and a range of important comorbidities. Treatment plans require an interdisciplinary mindset, because no treatment is the answer for all patients.5 12 Well designed clinical trials are needed to convince policy makers, patients, and practising clinicians of the long term usefulness of these tailored approaches.