Reduced risk of physician‐diagnosed asthma among children dwelling in a farming environment

Abstract

Background and objective: Living in a farm environment has been reported to be associated with lower prevalence of asthma, based on the results of cross‐sectional studies. The objective of this longitudinal study was to determine whether living in a farm environment is associated with lower incidence of asthma among children. Methods: A total of 13 524 asthma‐free children aged 0–11 years were drawn from the Cycle 1 (1994/1995) of the Canadian National Longitudinal Survey of Children and Youth (NLSCY). Subjects were categorized as dwelling in rural farming, rural non‐farming and non‐rural environments. Incidence of physician‐diagnosed asthma was determined at Cycle 2 (1996/1997). Bootstrap logistic regression method was used to adjust for design effect in the NLSCY. Results: The 2‐year cumulative incidence of asthma was 2.3%, 5.3% and 5.7% among children living in farming, rural non‐farming and non‐rural environments, respectively. From the multivariate analysis with adjustment for important confounders, children from a farming environment had a reduced risk of asthma compared with children from rural non‐farming environment with odds ratios (OR) of 0.22 (95% CI: 0.07–0.74) and 0.39 (95% CI: 0.24–0.65) for children with and without parental history of asthma, respectively. Children living in a non‐rural environment with parental history of asthma had an increased risk of asthma incidence when compared with children living in rural non‐farming environment (OR = 2.51, 95% CI: 1.56–4.05). Conclusion: This longitudinal study expands on observational study results which suggest a reduced risk of developing asthma associated with living in a farming environment.