Overview

Comorbidities in severe asthma are common, they complicate management and effect patient outcomes. Comorbidities may frequently interact, contribute to poor disease control and mimic symptoms of asthma. They may also increase the cost of treatment for people with severe asthma and lead to overtreatment. It is therefore recommended that comorbidities be addressed in severe asthma (Chung et al. 2014). Multidimensional assessment of severe asthma, as part of a treatable traits approach, allows for the recognition of these comorbidities and has been shown to improve patient outcomes (McDonald et al. 2020, McDonald et al, 2024 & Clark et al. 2017). In this module, we deal with the most common comorbidities associated with severe asthma, we present their prevalence and impact and provide recommendations for assessment and management.

Many comorbidities are more prevalent in people with severe asthma than in mild-moderate asthma, or in the healthy population. Their prevalence in a difficult-to-treat asthma cohort (most of whom had severe asthma) is shown below.

While respiratory physicians are adept at recognising some comorbidities (such as obstructive sleep apnoea, bronchiectasis and COPD), others often go undiagnosed even in specialist practice (such as dysfunctional breathing and inducible laryngeal obstruction) (Radhakrishna et al. 2017).

There is also data to show that the presence of multiple morbidities is also associated with greater asthma severity. Across five cohorts across the globe, a worse multimorbidity score (assessing rhinitis, reflux disease, breathing pattern disorder, obesity, bronchiectasis, anti-inflammatory drug-exacerbated disease, and obstructive sleep apnoea) correlated with worse asthma severity scores (Kurukulaaratchy et al. 2025).

It is understood that people with severe asthma present with heterogeneous disease expression. Cohort analyses show that for many patients with severe asthma, the presence and impact of comorbidities may be the dominant clinical feature, overshadowing airway centric features of inflammatory phenotype or variable airflow limitation (Lin et al. 2023).

Based mainly on observational studies, treatment of many comorbidities appears to improve asthma outcomes (Porsbjerg et al. 2017, Tay et al. 2017). Furthermore, using a treatable traits approach allows for targeted therapy that is measurable and treatable, which improves both asthma and the comorbidity (McDonald et al, 2020. & McDonald et al. 2024).With this approach, treatment outcomes for difficult-to-treat asthma patients with comorbidity-dominant profiles can be comparable to those with airway-centric profiles amenable to biologic treatment (Lin et al. 2023).

The multitude of patient comorbidities to be considered during severe asthma evaluation presents a clinical challenge. An unstructured approach is likely to miss several issues. On the other hand, exhaustive evaluation with every possible diagnostic test would be costly in resources and time. A third option is to employ a stratified approach, shown below.

This commences with the use of validated screening questionnaires for each comorbidity. An overview of validated screening tools is included below. As an example, the following scored and validated questionnaires and there sensitivity / specificity are proposed for screening by (Radhakrishna et al. 2017)

• Sinonasal Questionnaire (SNQ) for sino-nasal disease
• Score for Allergic Rhinitis (SFAR) for allergic rhinitis
• Nijmegen Questionnaire for dysfunctional breathing
• Pittsburgh Vocal Cord Dysfunction Index (PVCDI) for inducible laryngeal obstruction
• Berlin Questionnaire for obstructive sleep apnoea
• Hospital Anxiety and Depression Scale (HADS) for anxiety & depression
• Gastroesophageal Reflux Disease Questionnaire (GERD-Q) for gastro-oesophageal reflux disease

For further details see the Comorbidity Components Resources section of this website.

Such an approach has been shown to increase detection of comorbidities compared to clinical consultation alone (Radhakrishna et al. 2017). Positive questionnaires guide the clinician to confirm the likelihood of comorbidities being present, and prompt appropriate further management.

A systematic approach to addressing severe asthma comorbidities in patients is clinically effective. A recent meta-analysis of three severe asthma programs which addressed comorbidities systematically as part of their protocol demonstrated improvements in asthma control, asthma quality of life and exacerbation rate (Clark et al. 2017).

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