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 longterm 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.
Woolcock Institute for Medical Research, Sydney, NSW, Australia.
Gea
G
de Meer
Brett G
BG
Toelle
Kitty
K
Ng
Euan
E
Tovey
Guy B
GB
Marks
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000818:Animals; D000829:Animals, Domestic / Q000276:immunology*; D001249:Asthma / Q000453:epidemiology / Q000517:prevention & control*; D002415:Cats / Q000276:immunology*; D015331:Cohort Studies; D005500:Follow-Up Studies; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000453:epidemiology / Q000517:prevention & control*; D009517:New South Wales / Q000453:epidemiology; D013997:Time Factors