~ by Linda M. Girgis, MD
We have started to explore the complications obesity can cause. This post will look at its association with sleep apnea. The role of obesity in sleep apnea has been well established in adults and children alike. Its rate has been climbing.
The prevalence of OSA in obese patients is nearly twice that of normal weight patients. Patients with mild OSA who gain 10% of their baseline weight have at a sixfold-increased risk of progression of OSA. Similarly, a loss of an equal amount of weight can lead to more than 20% improvement in OSA severity. Some recent studies show that obese children have a 46% prevalence of OSA when compared with children seen in a general pediatric clinic (33%).
Why does obesity cause OSA?
It is felt that deposits of fat in specific areas play a key in determining whether someone develops OSA. For instance, fat deposits in the tissues surrounding the upper airways can result in a narrower lumen and increased collapsibility of the upper airway. In addition, truncal obesity reduces chest compliance, functional residual capacity, and increased demand for oxygen. Nevertheless, the relationship between OSA and obesity is much more complex. Patients with OSA tend to have reduced physical activity and cravings for carbohydrates that tend to exacerbate the obesity. CPAP has been shown to reduce the visceral fat in some patients. There have been some studies showing an interplay of obesity and OSA as a result of genetic factors, specifically polymorphisms of the leptin receptor.
It is even more alarming that we see this more frequently in children and adolescents. In one study, 46 children were evaluated. These subjects were recruited from a pediatric obesity clinic at a university hospital. They had been referred there by their primary care providers. They were compared to 44 normal weight subjects who were matched for other characteristics, such as sex and age. This study showed that mild breathing disruptions, however, they were more significant in obese subjects. It was also shown that many of them had enlarged tonsils and adenoids, so suggested ENT consult in cases of OSA in children despite their BMI. An interesting observation in this study is that oxygen desaturations were not as severe as in adults with OSA and, therefore, children with OSA did not suffer from daytime sleepiness as much.
The Sleep AHEAD study showed that there was a clear improvement in OSA in patients who lost weight. This study included 264 subjects in 4 different centers. Their average BMI was 36.7 and average apnea-hypopnea index (API) 23.2 events per hour. This study showed that clearly weight loss improved OSA, especially in men and those with higher AHI scores. In patients who maintained their weight for one year, they maintained their benefits of their weight loss as evidenced by their repeated AHI scores.
Obesity clearly plays an etiologic role in OSA in both adults and children. We are learning the dangers of OSA as time goes on, in terms of hypertension and cardiovascular disease. While obesity itself has a clear cause of producing OSB, it appears to be multi-factorial. Weight loss has been clearly demonstrated to improve OSA in many studies. The treatment should start with lifestyle changes and weight loss.
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Dr. Linda Girgis MD, FAAFP is a family physician in South River, New Jersey. She has been in private practice since 2001. She holds board certification from the American Board of Family Medicine and is affiliated with St. Peter’s University Hospital and Raritan Bay Hospital. She teaches medical students and residents from Drexel University, UMDNJ, and other institutions. Dr. Girgis earned her medical degree from St. George’s University School of Medicine. She completed her internship and residency at Sacred Heart Hospital, through Temple University. She has appeared in US News and on NBC Nightly News.