Farm Exposure and Atopy in Men and Women: The Saskatchewan Rural Health Study

Associations between farming exposures and atopy can vary by timing of exposure and sex. We examined associations between adult atopy, sex, and farm living in a rural Canadian population. In 2010, we conducted a baseline survey of 11,982 households located in four agricultural regions of Saskatchewan, Canada. Of the 7225 adults aged 18-75, 1658 underwent clinical assessments including skin testing. Of these, 1599 participants underwent skin prick testing to four common allergens. We defined atopy as >3 mm reaction to any of four allergens compared with saline control. Farming exposures were farm living in the first year of life and current farm living. All analyses were stratified by sex. The prevalence of atopy was 17.8% and was higher in men than women (P < .001). The most common allergy was to grasses (8.8%) followed by house dust mite (HDM) mixed (8.1%). Atopy was lower in those subjects with an early farm exposure (P = .08) and who were female (P = .03). After adjusting for education, age, and smoking status, both current and early farm exposures were associated with decreased sensitization to cat atopy in women that was stronger with current exposure (P < .05). Men had significantly decreased atopic sensitization to Alternaria with an early farm exposure and increased atopic sensitization to HDM with a current farm exposure. In this rural population, the protective effect of an early farm exposure for any atopy was weak overall. The impact of farming exposures on atopy was allergen dependent and varied by sex.