New research confirms that weight loss reduces obstructive sleep apnea in obese men, with the greatest effect seen in patients with severe disease.
Obstructive sleep apnea is a common sleep disorder characterized by pauses in breathing during sleep. Each episode (apnea) lasts for at least 10 seconds and is caused by the collapse of the upper airways during sleep.
Obstructive sleep apnea is a sleep-related breathing disorder that involves pauses in breathing during sleep. Obstructive sleep apnea occurs when the muscles relax during sleep, causing soft tissue in the back of the throat to collapse and block the upper airway. This leads to partial reductions (hypopneas) and complete pauses (apneas) in breathing that last at least 10 seconds during sleep. A common measurement of sleep apnea is the apnea-hypopnea index (AHI). This is an average that represents the combined number of apneas and hypopneas that occur per hour of sleep.
Moderate and severe obstructive sleep apnea (defined as 15 or more apneas per hour) carries an excess risk of motor vehicle crashes, heart disease and death. Yet only one study has examined the effects of weight loss on obstructive sleep apnea.
For the current study, the researchers set out to evaluate whether treatment with a low energy diet reduces moderate and severe obstructive sleep apnea in obese men. The study involved 63 obese men (BMI 30-40) aged 30-65 years with moderate to severe obstructive sleep apnea who were being treated with continuous positive airway pressure (CPAP).
Thirty men received a liquid very low energy diet for seven weeks to promote weight loss, followed by two weeks of gradual introduction of normal food. The remaining men acted as a control group by adhering to their usual diet over the nine weeks. Both groups attended regular clinical examinations throughout the study to measure weight, waist circumference, and body fat, and to test dietary compliance. For the diet group, each visit also included a one hour group session to build group support and provide motivation.
At the start of the study, both groups had a mean AHI of 37 apneas per hour. At week nine, the diet group had a mean AHI of 12 events per hour compared with 35 events per hour in the control group. The diet group also lost an average of 18.7 kg in weight compared with 1.1 kg in the control group over the nine-week period. Twenty-two out of 30 (73%) patients in the diet group were no longer obese at the end of the study, whereas all control patients remained obese. Five out of 30 (17%) patients in the diet group were also disease-free by the end of the study, and half had only mild obstructive sleep apnea, whereas all patients in the control group except one still had moderate to severe obstructive sleep apnea.
Treatment with a low energy diet improves obstructive sleep apnea in obese men, with the greatest effect in patients with severe disease, conclude the authors. Long term treatment studies are needed to validate weight loss as a primary treatment strategy for obstructive sleep apnea.
References:
1. Kari Johansson, et al. Effect of a very low energy diet on moderate and severe obstructive sleep apnoea in obese men: a randomised controlled trial. British Medical Journal. BMJ 2009;339:b4609. December 2009, doi:10.1136/bmj.b4609.
