Risk factors for new-onset cat sensitization among adults: a population-based international cohort study.

BACKGROUND: Cat exposure during childhood has been shown to increase the risk of developing cat sensitization, while the effect of cat exposure in adulthood has not yet been established.
OBJECTIVE: To evaluate new-onset sensitization to cat in adulthood in relation to changes in cat keeping.
METHODS: A total of 6292 European Community Respiratory Health Survey I (ECRHS I) participants aged 20 to 44 years from 28 European centers, who were not sensitized to cat, were reevaluated 9 years later in ECRHS II. Present and past cat ownership and total and specific IgE levels were assessed in both surveys. Allergen-specific sensitization was defined as a specific serum IgE level of 0.35 kU/L or more.
RESULTS: A total of 4468 subjects did not have a cat in ECRHS I or ECRHS II, 473 had a cat only at baseline, 651 acquired a cat during the follow-up, and 700 had a cat at both evaluations. Two hundred thirty-one subjects (3.7%) became sensitized to cat. In a 2-level multivariable Poisson regression model, cat acquisition during follow-up was significantly associated with new-onset cat sensitization (relative risk = 1.85, 95% CI 1.23-2.78) when compared with those without a cat at both surveys. Preexisting sensitization to other allergens, a history of asthma, nasal allergies and eczema, and high total IgE level were also significant risk factors for developing cat sensitization, while cat ownership in childhood was a significant protective factor.
CONCLUSION: Our data support that acquiring a cat in adulthood nearly doubles the risk of developing cat sensitization. Hence, cat avoidance should be considered in adults, especially in those sensitized to other allergens and reporting a history of allergic diseases.