Strength of association between comorbidities and asthma: a meta-analysis

The strength of association between comorbidities and asthma has never been ranked in relation to the prevalence of the comorbidity in the nonasthma population. We investigated the strength of association between comorbidities and asthma.

A comprehensive literature search was performed for observational studies reporting data on comorbidities in asthma and nonasthma populations. A pairwise meta-analysis was performed and the strength of association calculated by anchoring odds ratios and 95% confidence intervals with the rate of comorbidities in nonasthma populations via Cohen's d method. Cohen's d=0.2, 0.5 and 0.8 were cut-off values for small, medium and large effect sizes, respectively; very large effect size resulted for Cohen's d >0.8. The review was registered in the PROSPERO database; identifier number CRD42022295657.

Data from 5 493 776 subjects were analysed. Allergic rhinitis (OR 4.24, 95% CI 3.82-4.71), allergic conjunctivitis (OR 2.63, 95% CI 2.22-3.11), bronchiectasis (OR 4.89, 95% CI 4.48-5.34), hypertensive cardiomyopathy (OR 4.24, 95% CI 2.06-8.90) and nasal congestion (OR 3.30, 95% CI 2.96-3.67) were strongly associated with asthma (Cohen's d >0.5 and ≤0.8); COPD (OR 6.23, 95% CI 4.43-8.77) and other chronic respiratory diseases (OR 12.85, 95% CI 10.14-16.29) were very strongly associated with asthma (Cohen's d >0.8). Stronger associations were detected between comorbidities and severe asthma. No bias resulted according to funnel plots and Egger's test.

This meta-analysis supports the relevance of individualised strategies for disease management that look beyond asthma. A multidimensional approach should be used to assess whether poor symptom control is related to uncontrolled asthma or to uncontrolled underlying comorbidities.