By Dr. Enrique Diaz Guzman, Assistant Professor of Medicine and Associate Program Director at the Pulmonary and Critical Care Fellowship, University of Kentucky
Patients with COPD have an increase risk of developing diabetes, and the risk appears to exist regardless of the severity of COPD. For example, a large population study published in 2008 found that people with COPD had almost a double risk of being diagnosed with diabetes. Similarly, almost half of all COPD patients suffer from other medical problems frequently linked to diabetes, such as elevated blood pressure and higher levels of cholesterol. The combination of these medical problems is sometimes referred as “metabolic syndrome” and is considered a cause of cardiovascular problems.
It is unknown why people with COPD are affected with diabetes more often, but it is thought to be the consequence of the systemic inflammation associated with lung disease, although it is likely that the use of systemic corticosteroids and inhaled corticosteroids also contribute significantly to this elevated risk.
Elevated levels of blood glucose are associated with abnormal lung function, even in people without COPD. For example, studies report that young individuals with type 1 diabetes experience up to 20% decline in lung function. Although this decline may not be necessarily associated with worsening of symptoms in people without pulmonary problems, it may significantly contribute to worsening symptoms in people with COPD.
Diabetes can affect lung function in several different ways. For example, it has been associated with a reduction in lung volumes (this reduction is also known as lung restriction), as well as a reduction in forced expiratory volume in the first second (FEV1) – a direct indicator of the severity of airflow obstruction in COPD. The causes for this “restrictive” phenomenon are not well understood, but thought to be a consequence of the effects of high glucose levels on important breathing structures such as the diaphragm, and other breathing muscles as well as breathing nerves. Additionally, diabetes causes a reduction in the ability of the lung tissue to transfer oxygen (diffusing capacity).
Similarly, large longitudinal studies have found that diabetes causes an accelerated lung function decline compared to non-diabetics. Furthermore, uncontrolled diabetes is linked to worse outcomes (longer hospital stay and risk of death) in people that suffer from an exacerbation of COPD. Finally, diabetes also is associated with an abnormal brain control of the breathing pattern and can cause sleep-breathing disorders.
Importantly, the adverse effects of diabetes on lung function appear to be stronger among people who smoke tobacco. Fortunately for many patients, the risks associated with diabetes can be minimized by procuring adequate diabetic control and by reducing risk factors that favor lung function decline such as active or passive smoking. In addition, pulmonary rehabilitation and exercise programs are important to improve symptoms and glucose control.
Other important things to consider are: a) the use of prophylactic vaccination (influenza and pneumonia vaccines), as people with COPD and diabetes are at a higher risk of acquiring respiratory illnesses; and, b) adherence to medical regimens prescribed by your healthcare provider whether you have COPD, diabetes, or both, is key to control both diseases and prevent complications.
In conclusion, diabetes is more common in people with COPD and constitutes an important cause of complications. Adequate diabetic control is key for all patients with COPD, particularly for those who have severe COPD and are at risk of cardiovascular problems and COPD exacerbations. Since there is significant overlap between these two diseases, if you have diabetes and have a history of smoking or other potential exposures and have any respiratory complains, you should ask your provider to test you for COPD. Likewise, if you have COPD, be sure your provider checks for diabetes, especially if you have a family history of diabetes or glucose intolerance.