Kilpeläinen M, Terho EO, Helenius H, Koskenvuo M. Allergy. 2002;57:1130–1135
Purpose of the Study.
To examine the relationship between childhood farm environments and allergic sensitization and asthma in young adulthood.
The 296 participants were Finnish first-year university students (median age, 21.5 years) recruited by questionnaire. One hundred fifty-two subjects (51%) had a history of asthma or wheezing and 144 (49%) had no history of asthma or wheezing.
Physicians in both pulmonary and dermatology subspecialties, who were blinded with respect to original questionnaire data concerning prior symptoms and farm environment, conducted baseline examinations. Pulmonary function tests and methacholine challenge tests were performed. Participants were considered to have current asthma if they had experienced clinical symptoms consistent with asthma, such as wheezing, shortness of breath, or cough associated with typical provoking factors, during the preceding 12 months and the results of methacholine challenge or pulmonary function tests were indicative of asthma. Skin prick tests and allergen-specific immunoglobulin E (IgE) tests with multiple indoor, outdoor, food, and latex allergens were performed. Data were analyzed to examine the effects of childhood farm environments on current asthma and allergic sensitization, with adjustment for early childhood pet ownership.
Approximately 10% of subjects experienced childhood farm environments at 0 to 6 years of age, and the incidence of current asthma in the total study population was 10.7%. Significantly fewer patients with histories of farm environments had current asthma, compared with nonfarm participants (odds ratio [OR]: 0.22; 95% confidence interval [CI]: 0.07–0.70). No difference in bronchial hyperreactivity or skin test reactivity between groups was seen, although trends in favor of childhood farm environments were observed, with less bronchial hyperreactivity and fewer positive skin test results in this group. Farm environments had a protective effect on cat-specific IgE (OR: 0.10; 95% CI: 0.02–0.47), and participants in this group were more likely to have dust mite-specific IgE (OR: 3.29; 95% CI: 1.21–8.96).
Childhood farm environments were protective against asthma in young adulthood. Sensitization to cat allergens was more likely among participants from nonfarm environments, whereas dust mite sensitivity was more common among those from farm environments.
Although this study confirms previously described protective effects of farm environments on the development of asthma and allergic sensitization, results should be interpreted cautiously. The number of patients with a history of childhood farm exposure was small, making it difficult to make generalizations about larger populations with similar environmental histories. In addition, the conflicting findings on the protective effects of farm environments against sensitization to cat and dust mite allergens warrant more investigation.