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A comorbid medical disease is a condition that occurs in addition to the primary illness. For example, a person can have co-existing asthma (primary illness) and obesity (comorbid condition).

Some comorbid conditions make asthma more difficult to control. Important asthma comorbidities are:

  • Hay fever (allergic rhinitis)
  • Allergic bronchopulmonary aspergillosis
  • Obesity
  • GERD (gastroesophageal reflux disease)
  • Obstructive sleep apnea
  • Anxiety and depression

Hay fever (Allergic rhinitis)

Hay fever is an allergic condition triggered by pets, dust-mites, mold, and pollen.1 Symptoms mainly affect the nose, including runny nose, nasal congestion, and sneezing. Since hay fever and asthma affect the upper and lower parts of the same airway, it is not surprising that they are closely linked. Having hay fever increases your risk of having asthma. For many people, treating hay fever improves asthma symptom.2

Allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is an allergic reaction to Aspergillus fumigatus, a fungi found in soil.3 This fungi does not affect people with healthy immune systems. However, in people with asthma, it can damage to the lungs and airways. Signs of a reaction are high blood eosinophils, fever, and mucus with brown flecks.2 A chest x-ray or CT scan will show signs of damage. ABPA is treated with an oral corticosteroid and occasionally, with an antifungal medication. There is good evidence that treating ABPA can improve asthma control.2


Extra body weight changes the way the lungs function. It also alters the immune system and increases inflammation in the body.2,4 Obese adults are more likely than lean adults to develop asthma.2,4 Children and adults who are obese are more likely to have persistent and severe asthma.2 Asthma medications do not work as well in people who are very overweight.4 Additionally, obesity increases the risk of other conditions, such as GERD and obstructive sleep apnea.


GERD is a digestive disorder. Common symptoms of GERD are heartburn, regurgitation, chest pain, and dry cough.5 These symptoms happen when stomach contents such as food, fluid, and digestive juices back up into the esophagus (food pipe). GERD can lead to more asthma symptoms, especially at night. Treating GERD with medications can reduce nighttime asthma symptoms and asthma attacks.2

Obstructive sleep apnea

It can be difficult to tell obstructive sleep apnea apart from nighttime asthma. Both conditions have similar symptoms. In fact, they often overlap in the same patient.2 Sleep apnea can be a cause of poorly controlled asthma.2 Diagnosis of sleep apnea requires a sleep study. Nasal CPAP (continuous positive airway pressure) is helpful for people with comorbid asthma and sleep apnea, but not for people with asthma alone.2

Anxiety and depression

Mental health problems do not cause asthma, but they do make asthma harder to control.2 Anxiety and depression can get in the way of taking care of your asthma. This leads to more asthma symptoms and asthma attacks. People with mental health problems have more emergency department visits for asthma.5 Anxiety and asthma cause similar symptoms, such as shortness of breath and chest tightness. Furthermore, asthma symptoms cause more distress for people with mental health problems.6 It is not known whether treating anxiety and depression can improve asthma.6

Written by: Sarah O'Brien | Last Reviewed: May 2016.
  1. MedlinePlus. Allergic rhinitis. Accessed 2/12/15 at:
  2. National Heart, Lung, and Blood Institute. Expert panel report 3 (EPR-3): Guidelines for the diagnosis and management of asthma - Full Report 2007. Accessed 11/12/14 at:
  3. American Academy of Allergy, Asthma, and Immunology. Allergic bronchopulmonary aspergillosis (ABPA). Accessed 2/12/15 at:
  4. Pradeepan S, Garrison G, Dixon AE. Obesity in asthma: approaches to treatment. Curr Allergy Asthma Rep. 2013;13:434-442.
  5. Global Initiative for Asthma. Global Strategy for Asthma Management and Prevention 2014. Accessed 11/12/14 at:
  6. Thomas M, Bruton A, Moffat M, Cleland J. Asthma and psychological dysfunction. Prim Care Respir J. 2011;20:250-256.