Is Obstructive Sleep Apnea Caused by Obesity?

OSA and obesity

July 16, 2019
By Lisa Ferreira, MD

What Is Obstructive Sleep Apnea?

Obstructive sleep apnea (OSA) is an increasingly common condition affecting approximately 20-30% of men and 10-15% 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 OSA 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, and 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 events are happening per hour.

What Is the Connection between Obesity and OSA?

Obesity is a well-known risk factor for developing OSA. The prevalence of OSA in men and women increases as 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 1,000 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 had obesity (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? OSA most often results from a collapse in the upper airway leading to decreased airflow to the lungs. This collapse of the upper airway 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, neck circumference 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 upper airway.

In addition, people with obesity can experience a condition called obesity hypoventilation syndrome (OHS). This condition has been shown to present in over 50% of people with a BMI over 50. OSA has also been found to present in approximately 90% of people with OHS. Additional body weight exerts pressure on the chest, which decreases the ability of the lungs to expand fully and therefore, to 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 upper airway more likely to collapse.

What Are the Treatment Options for OSA?

OSA is a chronic condition that 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 (CPAP) machine is most commonly the first step in OSA treatment. 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 result 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 four (Tuomilehto HP, et al, Am J Respir Crit Care Med. 2009;179(4):320.).

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