Collapsing airways caused during sleep are caused by a common sleep apnea called obstructive sleep apnea (OSA), characterized by paused breathing while sleeping, with each apnea episode lasting for at least 10-seconds.

While, moderate and severe obstructive sleep apnea defined as 15-plus apneas per hour carries an excess risk of causing motor vehicle crashes, heart disease and death. Even so, only one study that by researchers at the Karolinska Institute in Sweden, have so far examined weight loss effects on obstructive sleep apnea.

The Swedish researchers evaluated whether a low energy diet treatment could reduce moderate and severe obstructive sleep apnea in men, considered obese.

Sixty-three obese men with a body mass index of (BMI) of 30-40 and aged 30-65 years, suffering from moderate to severe obstructive sleep apnea, and who were being treated with continuous positive airway pressure i.e. a mask that helped them breathe whilst they slept, participated in the study.

Divided into two groups, 30-men in the first group were put on a liquid low energy diet for 7-weeks for promoting weight loss, after which for two weeks they were gradually introduced to normal food. The remaining men acting as the control group stuck to their usual diet over the 9-weeks of the study's duration.

Before the study began, both groups had a mean apnea hyperpnoea index (AHI) of 37-apneas per hour. However, by the ninth week, the diet group's mean AHI was 12-events per hour, as compared to 35-events per hour for the control group.

Further, the study findings also show, over the 9-week period the diet group lost an average of 18.7-kg., compared to 1.1-kg. for the control group, with 22 out of 30-diet group patients no longer considered obese, including 5 out of the 30 being disease free at the end of the study and half having only mild disease, whereas all control patients remained obese, and with the exception of one, all still suffered from moderate to severe disease.

In conclusion, the researchers believe a low energy diet treatment improves obstructive sleep apnea in obese men, having the greatest effect on patients with a severer form of the disease.

The study has been published on BMJ.com