For obese men, a dramatic weight loss can be an effective way to improve moderate to severe sleep apnoea, scientists at Karolinska Institutet report. Those with severe sleep apnoea when the study began benefited most from weight loss.
"Our findings suggest that weight loss may be an effective treatment strategy for sleep apnoea in obese men," says Kari Johansson, one of the researchers involved in the study.
Sleep apnoea -- the temporary cessation of breathing during sleep -- is a relatively common but under-diagnosed disease. Five or more such events per hour is considered a disease. Untreated, sleep apnoea is associated with an increased risk of traffic accidents, as well as stroke and heart disease, for example. Moderate and severe sleep apnoea also increases the risk of premature death. It has long been known that people with overweight or obesity are more likely to develop the disease, and that men are more affected than women.
Obstructive sleep apnoea is a common sleep disorder characterised by pauses in breathing during sleep. Each episode (apnoea) lasts for at least 10 seconds and is caused by the collapse of the upper airways during sleep.
Moderate and severe obstructive sleep apnoea (defined as 15 or more apnoeas 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 apnoea.
In a randomised study published in the British Medical Journal, researchers at Karolinska Institutet examined if weight-loss can help to cure moderate and severe sleep apnoea. The study included 63 obese men (BMI between 30 and 40) aged between 30 and 65. The participants had moderate to severe sleep apnoea as measured by the AHI (apnoea-hypopnea) index. All participants had symptom alleviation treatment through CPAP -- continuous positive airway pressure -- which produces more normal breathing patterns during sleep. The participants were randomly assigned to two groups, one of which underwent an intense weight-loss programme, the other served as a control group, for a period of nine weeks.
The results of the study show that the weight loss group lost 19 kilos on average after nine weeks and more than halved the number of apnoea events. None of the treated patients had severe sleep apnoea, half had only mild sleep apnoea and one in six could be declared healthy. The researchers also noted that the effect of the weight loss programme was greatest in patients with severe sleep apnoea.
To achieve significant weight loss, the treatment group were put on a very low calorie diet (VLCD), which gave them an initial energy input of 554 kcal per day for seven weeks followed by a fortnight's successive increase up to 1,500 kcal per day at week nine. The control group maintained their normal dietary habits during the nine week study period, but was afterwards offered a VLCD programme.
After the VLCD period, the participants were also invited to take part in a year s behavioural change programme to help them maintain their weight loss.
"We often use VLCD in the form of a low calorie powder as part of the treatment of obese patients with a serious comorbidity, such as sleep apnoea," says Ms Johansson. "The powder is mixed with water and replaces every meal of the day, which gives a rapid loss of weight. It s also a good way of boosting the patients' motivation."
The researchers stress that the VLCD diet is not a general solution to weight problems, but something mainly to be used in the first phase of a long-term treatment programme. To keep the weight off, patients need to work hard to improve their dietary and exercise habits, usually with the aid of a long-term behaviour modification programme. Drugs can also be used in the post-weight loss phase to further improve weight loss maintenance.
The current study was part funded by Cambridge Manufacturing Company Limited, which markets the Cambridge Diet, the low-calorie powder used in the study. The company had no influence on the study, the analyses or the collation of the results. Examples of similar VLCD products marketed by other companies are Nutrilett, Naturdiet and Allevo. The researchers who conducted the study work at the Obesity Unit, Karolinska University Hospital, Huddinge, and the Clinical Epidemiology Unit, Karolinska Institutet.
- Johansson et al. Effect of a very low energy diet on moderate and severe obstructive sleep apnoea in obese men: a randomised controlled trial. BMJ, 2009; 339 (dec03 1): b4609 DOI: 10.1136/bmj.b4609
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