04/01/2009 - Articles

Link found between disordered sleep and calorie expenditure

By: Susan Aldridge, medical journalist, PhD

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A new study shows that people with worsening sleep-related breathing disorders have increased expenditure of calories at rest during the day. These findings suggest the relationship between disorders like sleep apnea and obesity is a complex one worthy of further investigation.

Summary

Breathing abnormalities during sleep, like sleep apnea, are often linked to obesity. A new study shows that as the breathing gets worse, so the resting caloric expenditure increases. This suggests a link between altered metabolism and sleep disordered breathing which may impact on the obesity issue.

Introduction

Breathing abnormalities during sleep include snoring and sleep apnea, where breathing actually stops during sleep. These disorders are linked to obesity and can lead to serious long-term health problems, like stroke. Obese people tend to have obstructed upper airways which lead to breathing problems. But we don't really know whether obesity contributes to disorders like sleep apnea, or are a result of them. We need to know more about the role played by metabolism in sleep related breathing abnormalities.

What was done

Researchers at the University of California, San Francisco, assessed resting caloric energy expenditure in 212 adults with signs or symptoms of sleep-related breathing disorders. Their medical histories were taken and they also underwent physical examination and sleep monitoring to estimate the severity of their breathing disorder.

What was found

There were differences between resting caloric energy expenditure depending on the severity of sleep apnea symptoms. The average value for the group was 1,763 calories per day. For those with severe symptoms, it was higher at 1,999 calories per day and for those with mild symptoms it was lower at 1,626 calories per day.

What this study means

Body weight depends upon the balance between caloric intake and total daily caloric expenditure, of which the resting caloric expenditure measured here is just a component. At first sight, these results seem counter-intuitive - suggesting that those with the worst breathing symptoms ought to be slimmer because they are expending more energy during the day. But the researchers point out that this is just one factor in the equation. Sleep disorders may alter metabolic rate directly in ways we do not fully understand. They may also alter energy intake and, though daytime fatigue, reduce total energy expenditure. Clearly there is far more to be learned about the relationship between sleep disordered breathing and body weight.

Source

Kezirian EJ et al Breathing problems during sleep associated with calories burned at rest Archives of Otolaryngology December 2008

Created on: 01/02/2009
Reviewed on: 04/01/2009

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