A total of 377 responders indicated any
respiratory symptoms on the questionnaire. Using the index
of respiratory symptoms as the outcome in a linear model,
using age (pZ 0.956), smoking history (pZ 0.004), or
gender (p Z 0.312) as exploratory variables did not identify
any difference in the prevalence of respiratory symptoms
between the two groups (farmer vs. non-farmer, p Z0.07).