Asthma prevalence and morbidity among rural Iowa schoolchildren

There are conflicting findings about the prevalence of asthma among farm and nonfarm children. We sought to estimate asthma prevalence and morbidity and determine differences between farm and nonfarm children. The study population consisted of all children aged 6 to 14 years enrolled in 10 school districts in 2 noncontiguous rural Iowa counties from 2000 through 2002. The mailed parental screening questionnaire included the International Study of Asthma and Allergies in Childhood core questionnaire, items from the Functional Severity Index, and items on physician diagnosis and medication and urgent care use. The response rate was 86.6%. The 12-month prevalence of wheeze was 19.1%. Self-reported physician diagnosis of asthma was reported by 13.4%. On multivariable analysis controlling for age, sex, and county, children who lived on farms were less likely than those who lived in town to have ever wheezed (odds ratio, 0.71; 95% CI, 0.58-0.87) or to have wheezed during the past year (odds ratio, 0.77; 95% CI, 0.60-0.98). However, this protective association with farming was only observed in one of the study counties. Among those who wheezed, farm and nonfarm children were equally likely to have been given a diagnosis of asthma and had comparable morbidity. By using a standardized questionnaire with a high response rate in this large, rural, population-based study, asthma prevalence rivaled that in large Midwestern cities. Unmeasured risk factors might account for the apparent protective effect in Keokuk County. These findings cast doubt on a protective effect of rural life for the development of childhood asthma.