Overlap Syndrome

example of gas exchange in the lungs for copd overlap syndrome blog post

Chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) are two of the most common pulmonary diseases. Unfortunately, they can also occur simultaneously in a phenomenon commonly referred to as Overlap Syndrome, creating twicefold the unpleasant conditions of disordered breathing.

This leads to long-term chronic health problems beyond the lungs (such as diabetes and heart disease) and their associated myriad complications.

The association between COPD as an obstructive lung disorder and OSA as a sleep breathing disorder means a person suffering from both has a compromised respiratory system that cannot even rely on sleeping at night for recovery or relief.

Why is this?

The endless struggle of Overlap Syndrome

Those with COPD struggle to maintain a healthy balance of oxygen and carbon dioxide in their bloodstream during the day.

If they also have OSA, this sleep breathing disorder kicks in as soon as they fall asleep. This leads to further imbalances to their blood chemistry.

While the rest of us rely on that nighttime period of consolidated sleep to maintain health and well being, and to recover from the stresses placed on our systems by chronic illness, those with Overlap Syndrome never catch a break.

This explains the term “overlap syndrome.” It's a way to reference the never-ending challenges of breathing for those suffering from both COPD and OSA.

(Those with asthma and OSA are also said to suffer from “alternative overlap syndrome” because, while asthma is no longer considered a part of the definition of COPD, its presence with sleep-disordered breathing at night leads to the same respiratory stresses and complications.)

Overlap Syndrome as a term was coined in the earlier part of this century when pulmonologists began to notice a couple of things:

  • Patients who have COPD or asthma are more likely to also suffer from OSA based on the very mechanisms of their daytime breathing problems, which become equally evident during the night as they sleep.
  • Patients who had either COPD or asthma, but not OSA, still had breathing problems, but they weren't as acute as those with the overlap of both.

While a person could have COPD or asthma, and not have OSA as well, the odds figure prominently that they will develop a sleep breathing disorder eventually. This is due to basic upper airway mechanisms that both kinds of disorders share.

Breaking down the overlap

Overlap Syndrome describes comorbidity (or the simultaneous presence) of two health conditions, COPD and OSA.

What is COPD?

COPD is defined by the Global Initiative for Chronic Obstructive Lung disease (GOLD) as:

A preventable and treatable disease with some significant extrapulmonary effects that may contribute to the severity in individual patients. Its pulmonary component is characterized by air-flow limitation that is not fully reversible. The air-flow limitation is usually progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases.

More simply put, people who suffer from chronic bronchitis or emphysema, or both, experience compromises to their breathing caused by damage from either (or both) illnesses. This makes it difficult for the body to exchange oxygen through inhalation and carbon dioxide through exhalation. Without this “gas exchange,” the chemistry of the blood is out of balance, and this can lead to a wide range of problems that can impact the organs, the cells, and overall ability by the body to maintain health and well being.

What is OSA?

We define OSA as the measurable collapse of the upper airway during sleep by a variety of means. This results in dangerous dips in blood oxygen levels as well as increases in carbon dioxide in the blood. Carbon dioxide is a waste product of cellular activity that needs to be exhaled (in exchange for inhalation of oxygen, hence “gas exchange”) in order to restore chemical balance to the bloodstream. A flooding of stress hormones signaled by the brain during apneas also creates arousals necessary to encourage breathing again. However, numerous lengthy apneas can create a constant state of stress on the heart, the lungs, and other organs. Severity of sleep apnea is based on the length and frequency of these collapses and their related arousals. Untreated OSA can contribute to the development of still other problems, like diabetes, kidney disease, and obesity, without active treatment to correct these obstructions.

Are COPD and OSA linked?

Studies have shown a prevalence of both OSA in those with COPD measuring between 11 and 19 percent of those who participated in research. Almost half of all people who have COPD experience some challenges with breathing while asleep, even if they don't have full-fledged OSA. People with COPD tend to have reduced levels of blood oxygen all day long, even while they are alert and breathing. When they fall asleep, obstructions to their airways caused by OSA can radically reduce these already reduced levels. This could be life threatening, depending upon severity. Also, both disorders originate through the same mechanisms, namely the dysfunction of the muscles and tissues of the upper and lower airways. This includes the connective organs and structures between the oral cavity (the mouth) and the respiratory system (the lungs). But it's important to note that, while both conditions are difficult to live with and to treat, those people with COPD and OSA have a much higher risk for worsening morbidity and early mortality, compared to those who only have one or the other, but not both disorders.

How is Overlap Syndrome identified and treated?


When COPD (or asthmatic) patients complain of sleep problems, the best way to address these is through an overnight sleep study. During this assessment, accurate measures of blood oxygen and breathing patterns can identify an underlying sleep breathing problem which could qualify as Overlap Syndrome. Once identified, new efforts to manage breathing during sleep can be prescribed. Guidelines established in 2010 by the American Thoracic Society also suggest that patients with less severe COPD who also suffer from pulmonary hypertension undergo overnight polysomnography to pinpoint hidden problems or customize treatment.


The main effort to treat Overlap Syndrome focuses on two things:
  • the maintenance of adequate blood oxygen at all times of the day
  • the prevention of sleep-disordered breathing (OSA)
The use of continuous positive airway pressure (CPAP), often in combination with supplemental oxygen, is a common approach. Weight loss for those who are obese, and proactive use of short- and long-term steroids to treat COPD symptoms, may also be part of the equation. Researchers are still refining their clinical definition of these combined conditions and seeking new and better ways to manage them. Still, the challenges of patient quality of life and morbidity still linger. This reality spotlights the need for patients with breathing disorders of all kinds to receive complete and accurate diagnoses so they can receive the best possible therapy.