Presence and timing of cat ownership by age 18 and the effect on atopy and asthma at age 28

Background: Asthma and allergic sensitization to cats frequently coexist, although recent studies show less atopic disease among people who had pets in infancy. However, no long-term evaluations have been performed thus far. Objective: We sought to evaluate the relationship between cat ownership at different age periods (< 18, > 18, and both periods and atopic disease at age 28. Methods: Australian school children aged 8 to 10 years were recruited in 1982 and participated in follow-up surveys until 2002. Cat ownership was defined by surveys in 1992 and 2002 as having a cat before age 18 only, after age 18 only, or in both periods of life. Health outcomes were defined at a mean age of 28.5 years. Results: Complete data were available for 224 subjects, 50 of whom had a cat before 18 years of age only, 14 after age 18 only, and 70 in both periods. Compared with 90 subjects that never had a cat, having a cat before age 18 protected against atopy to outdoor allergens, airway hyperresponsiveness (AHR) to histamine, current wheeze, and current asthma (P < .05). In contrast, subjects who acquired their first cat after age 18 showed a trend toward higher prevalence rates for asthma symptoms and AHR (P > .10). Conclusions: Having had a cat before 18 years of age protects against adult asthma and atopy.