Cat Exposure Not Linked to Worse Pediatric Asthma Outcomes

Key Takeaways

• Cat exposure was defined as parental cat ownership recorded in the National Cat Register in 2023, and 9.4% of the cohort (n=2,862) had recorded exposure.
• Asthma exacerbation occurred in 3.3% vs 3.5%, with adjusted OR 1.12 (95% CI 0.90–1.39), and moderate-to-severe asthma in 9.6% vs 10.1%, with adjusted OR 0.96 (95% CI 0.84–1.10).
• In the subset with ACT and spirometry data, no significant differences were seen for uncontrolled asthma, FEV1 z-score, or FEV1/FVC, and within exposed households the number of cats, cat sex, and cat age were not associated with asthma outcomes.

For families and clinicians, whether a household cat worsens symptoms in children who already have asthma and allergy remains uncertain, but a Swedish register-linked cohort study found no adjusted association between recorded parental cat ownership and worse short-term asthma outcomes in 30,277 children aged 4–17 years. The analysis addressed children with established asthma and allergy rather than asthma development or incidence, and recorded parental cat ownership was not associated with higher odds of exacerbation or medication-defined moderate-to-severe asthma during the study window. The findings were limited to measured outcomes during 2023–2024.

The study was a population-based Swedish register-linked cohort study, also described by the authors as a cross-sectional cohort study, including children born in Sweden between 2006 and 2020 who were aged 4–17 years and had validated asthma and allergy plus asthma care in the 2 years before exposure assessment. After 1,733 of 32,010 eligible children were excluded before final cohort assembly, the analyzed cohort had a median age of 9.5 years and 38.6% female participants.

Outcomes were assessed during 2023–2024 across a 24-month observation period, and asthma exacerbation was defined as an emergency or unplanned hospital or specialized-care visit with asthma as the primary diagnosis, or at least 4 SABA dispensations within 12 months, while moderate-to-severe asthma was defined by dispensed medications using adapted GINA treatment steps. These definitions framed the comparison between children with and without recorded parental cat ownership.

Subset analyses were available for 1,428 children with both ACT and FEV1 data, including 97 cat-exposed children, and adjusted analyses did not show significant differences by exposure in uncontrolled asthma, symptom control, or lung function. The reported estimates were an adjusted OR of 0.70 (95% CI 0.40–1.22) for uncontrolled asthma and a beta of -0.09 (95% CI -0.37 to 0.20) for FEV1 z-score, while FEV1/FVC data were available in 1,253 children and the beta was -0.01 (95% CI -0.02 to 0.005). No effect modification by age or sex was reported, with p for interaction values of 0.42 and 0.44. Across the subset analyses, the direction of results remained consistent with the main null findings.

Within the cat-exposed group, asthma exacerbation and asthma severity did not differ by number of cats, cat sex, or cat age, and similar null associations were seen after excluding children with dog exposure. The authors noted that the National Cat Register was established in 2023 and may have incompletely captured exposure, while allergen-specific IgE data, mono- versus polysensitization patterns, duration of ownership, and indoor-versus-outdoor cat status were unavailable. They also reported probabilistic bias analysis with bias-adjusted OR distributions above and below 1 across scenarios, leaving the direction of any underlying association uncertain, and the observational register-based design does not establish causality.

Among children with established asthma and allergy, recorded parental cat ownership was not associated with worse measured asthma outcomes over the study window.