Obstructive Sleep Apnea and Obesity

obstructive sleep apnea and obesity

May 21, 2019

What is Obstructive Sleep Apnea?

Obstructive sleep apnea (OSA) is an increasingly common condition affecting approximately 20 to 30% of men and 10 to 15% of women in North America.  OSA is a potentially life-threatening sleep disorder in which breathing significantly decreases or stops during sleep usually due to a collapse of the airway.  OSA is medically defined as having either 15 or more events when a person stops breathing during sleep or 5 or more events per hour in addition to daytime symptoms such as daytime sleepiness.

How is Obstructive Sleep Apnea diagnosed?

The evaluation for OSA is often started when a patient presents to his or her healthcare provider with a concern of increased fatigue.  Family members may also raise concerns about witnessing the patient snoring or not breathing at times during sleep. Common complaints from patients who have OSA are feeling tired when waking despite a full night’s sleep or falling asleep easily during inactive times such as being a passenger in a car or watching television.  In addition, patients frequently describe poor concentration, moodiness and morning headaches. Partners of patients with sleep apnea often times witness other common symptoms including snoring, choking or gasping for air during sleep as well as restless sleep. A healthcare provider can diagnose OSA by using a home sleep apnea test or an overnight in-lab sleep study to assess how many underbreathing or event are happening per hour.

Is Obesity an OSA risk factor?

Obesity is a well-known risk factor for developing OSA.  The prevalence of OSA in men and women increases as the body mass index (BMI) increases.   Other physical characteristics used to aid in diagnosis include neck circumference and waist-to-hip ratio. In a study of almost 700 adults, a 10% increase in weight was associated with a 6-fold increase in the risk of having OSA (Peppard PE, et al, JAMA. 2000;284(23):3015).  In another study of over 1000 adults, moderate to severe OSA was found in 11% of men and 3% of women of normal weight, 21% of men and 9% of women who were overweight and 63% of men and 22% of women who were obese (Tufik s, et al, Sleep Med.2010 May:11(5):441-6). Obesity is also the only completely reversible risk factor for OSA.  

Not only does OSA present in adults with obesity, but children with obesity are 46% more likely to have OSA than their normal-weight peers.

Is OSA caused by Obesity?

The risk of having OSA is certainly increased by having obesity but does obesity actually cause OSA?  As discussed above, OSA most often results from a collapse in the upper airway (UA) leading to decreased airflow to the lungs.  This collapse of the UA can happen for a few reasons, but, in obesity specifically, the thickness of the soft tissues of the neck can increase putting pressure on the pharynx.  The pharynx is a flexible tube in the neck susceptible to collapse if enough pressure is applied to it from the surrounding soft tissues. For this reason, the circumference of the neck is a valuable measurement when OSA is suspected.  It is also known that the size of the tongue can increase in people with obesity leading to further narrowing of the UA.

In addition, people with obesity can experience a condition called Obesity Hypoventilation Syndrome (OHS).  This condition has been shown to be present is over 50% of people with a BMI over 50. OSA has also been found to be present in approximately 90% of people with OHS.  The additional body weight exerts pressure on the chest which decreases the ability of the lungs to expand fully and, therefore, take in enough oxygen. It is thought that decreasing oxygen in the body can also weaken the tone of the muscles in the pharynx making the UA more likely to collapse.

What are OSA treatment options?

OSA is a chronic condition which requires a long-term treatment strategy.  The benefits of treating OSA include increases in energy level, concentration and mood disorders.  In addition, untreated OSA can increase the risk of heart disease and diabetes. A Continuous Positive Airway Pressure machine (CPAP) is most commonly the first step in treatment of OSA.  However, since obesity has been shown to contribute to the development of OSA, a highly effective long-term treatment is weight loss. Even a 10% weight loss can results in a 20% improvement in the severity of OSA.  One study of 72 patients with obesity found that with a weight loss of approximately 20 pounds, the number of events per hour decreased by an average of 4 (Tuomilehto HP, et al, Am J Respir Crit Care Med. 2009;179(4):320.).

In summary, OSA is a potentially dangerous sleep disorder commonly found in people with obesity.  There is, certainly, evidence that obesity can be among the causes of OSA, but also can potentially be reversed with weight loss.  It is always advisable to consult your doctor for an accurate assessment of your risks and for proper diagnosis.

This article was written by Lisa Ferreira, MD