Is asthma associated with cognitive impairments? A meta-analytic review

Introduction: Asthma is a chronic disease with significant health burden and socioeconomic and racial/ethnic disparities related to diagnosis and treatment. Asthma primarily affects the lungs, but can impact brain function through direct and indirect mechanisms. Some studies have suggested that asthma negatively impacts cognition, while others have failed to identify asthma-related cognitive compromise. We aimed to conduct a meta-analysis of cognition in individuals with asthma compared to that in healthy controls. We also examined the impact of some key potential moderators. Method: Data on cognitive outcome measures and sociodemographic, illness-related, and study-related variables were extracted from studies reporting cognitive test performance in individuals with asthma compared to that in controls. Results: There was no evidence of publication bias. A random-effects model examining differences in task performance between 2017 individuals with asthma and 2131 healthy controls showed significant effects in the small to medium range. Cognitive deficits associated with asthma were global, with strongest effects on broader measures involving academic achievement and executive functioning, but with additional impact on processing speed, global intellect, attention, visuospatial functioning, language, learning, and memory. Severity of asthma was a key moderator, with greatest cognitive deficits associated with severe asthma. Cognitive burden was also greatest in asthma patients who were younger, males, from low socioeconomic backgrounds, and from racial/ethnic minorities. Effects were independent of type of population (child versus adult), type of study (norm-referenced versus control-referenced), or reported use of oral or inhaled corticosteroid medications. Conclusions: There is cognitive burden associated with asthma, particularly among vulnerable groups with severe asthma. This could be due to increased risk of intermittent cerebral hypoxia in severe asthma. The clinical need to assess cognition in individuals with asthma is underscored.