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Sleep studies performed on 132 obese male and female patients has found a massive 64% suffered from obstructive sleep apnoea / apnea.

The study was conducted over three years and reported recently in the Journal of Sleep & Breathing.  Diagnostic sleep studies (polysomnograms) were performed on patients preparing to undergo gastric bypass surgery between January 2004 and January 2007. 

Where obstructive sleep apnoea / apnea (OSA) was found, it was graded as mild (less than 15 apnoeic events per hour of sleep), moderate (15 to 30 apnoeic events per hour of sleep) or severe (30 or more apnoeic events per hour of sleep), as indicated by the apnoea hypopnoea index / apnea hypopnea index (AHI).

The study also considered factors such as the patients’ gender, age, weight, height, body mass index, neck circumference, and waist circumference.  In the patients with OSA, body mass index (BMI), neck circumference and age were higher than in patients without OSA.  Waist circumference was not found to have any correlation with the existence of OSA, but BMI, age and male gender were each found to be independent predictors of sleep apnoea / apnea.

With the female patients, high BMI and age greater than 49 years were the only significant predictors of moderate or severe OSA.  The study found that men and women over 49 years of age have the greatest risk for OSA.   The prevalence of moderate or severe sleep apnoea / apnea was 71 percent in the male and 31 percent in the female patients.

The researchers recommend mandatory preoperative sleep studies for severely obese patients.

Interestingly, the existence of a sleep disordered breathing condition such as obstructive sleep apnoea / apnea has previously been found to be a cause of metabolic retardation.  This raises an interesting question:  Did the patients have a sleep disordered breathing condition in the first place which contributed to their obesity by slowing their metabolism?  Or was the patient’s sleep disordered breathing condition as a consequence of their obesity?

The relationship between obesity and sleep apnoea / apnea is probably circular.  That is, obese patients are more likely to suffer from a sleep disordered breathing condition.  At the same time, people with a sleep disordered breathing condition are more likely to have a slow metabolism and thus gain weight.  Treatment for both conditions (obesity and sleep disordered breathing, particularly obstructive sleep apnoea / apnea) should therefore be provided to patients who suffer from these co-morbidities.