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Strong cross-sectional association found between ADHD, asthma

Combined results of a meta-analysis and Swedish population-based study supported a significant link between ADHD and asthma, which remained after controlling for possible confounders.

“From a clinical and public health perspective, awareness of a significant association between these two conditions would prompt ADHD specialists to refer patients with early forms of asthma, and asthma specialists to refer patients with problems of inattention, hyperactivity, and impulsivity, for appropriate assessment, thus helping to reduce the diagnostic delay that is of concern for both ADHD and asthma,” Samuele Cortese, MD, PhD, from the Center for Innovation in Mental Health, University of Southampton, and the division of psychiatry and applied psychology, University of Nottingham School of Medicine, and colleagues wrote.

The investigators conducted a systematic review and meta-analysis of clinical databases for observational studies that examined the link between asthma and ADHD. Then, they performed a population-based study of individuals in multiple national Swedish registers to simultaneously control for all relevant confounders that varied across studies.

The researchers collected 2,649 citations, from which they obtained 49 datasets that included 210,363 participants with ADHD and 3,115,168 without. The data indicated a significant relationship between ADHD and asthma, demonstrating a pooled unadjusted OR of 1.66 (95% CI, 1.22-2.26) and a pooled adjusted OR of 1.53 (95% CI, 1.41-1.65).

There was a significant association between asthma and ADHD (pooled OR = 1.66; 95% CI, 1.22-2.26), according to results of the primary analysis. The researchers noted, however, that heterogeneity was high (I²=99.47) and Egger’s test showed potential for publication bias (P = .049). Among people with ADHD, the pooled prevalence of asthma was 16.9% (95% CI, 12-23) and among those without ADHD was 11.5% (95% CI, 9.813.4). Meanwhile, the pooled prevalence of ADHD was 8.8% (95% CI, 6.2-12.2) in those with asthma and 5·6% (95% CI, 4.5-7) in those without.

Results from the population-based study, which included 1,575,377 people — 259,253 [16.5%] of whom had asthma and 57,957 [3.7%] of whom had ADHD — demonstrated that asthma was significantly linked with ADHD (OR = 1.6; 95% CI, 95% CI, 1.57-1.63) after adjusting for sex and year of birth. Furthermore, this link remained significant after simultaneous adjustment for all covariates (OR = 1.45; 95% CI, 1.41-1.48).

“Overall, our study highlights the importance of considering associated systemic somatic dysfunctions in neurodevelopmental disorders such as ADHD and adds to the current debate around the integration of mental health and general medical care,” Cortese and colleagues wrote. “From a scientific perspective, the link between asthma and ADHD lends support to the possible involvement of inflammatory mechanisms in the pathophysiology of ADHD. Further longitudinal studies, rigorously controlling for possible confounders, are needed.” – by Savannah Demko

Disclosure: Cortese reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.