Association of farming with the development of cedar pollinosis in Japanese adults.

Purpose: Although cross-sectional studies have reported that the prevalence of allergy is reduced on a farm, few prospective studies were carried out on adults. We examined the association of experience of farming with occurrence of cedar pollinosis in a prospective cohort in Japan.

Methods: A total of 5,698 men and 6,533 women, aged 35 to 69 at baseline in 1992, participated in the Takayama Study, a population-based prospective cohort study. Occupational history was assembled via a self-administered baseline questionnaire. To obtain information on cedar pollinosis, a follow-up questionnaire after 10 years from baseline was administered in 2002.

Results: Compared with nonfarmers, farmers had a significantly reduced risk of cedar pollinosis after controlling for covariates (hazard ratio (HR): 0.61, 95% confidence interval (CI): 0.41, 0.90 in men; and HR: 0.31, 95% CI: 0.16, 0.60 in women). There was no significant association of cedar pollinosis with other occupations except for an increased risk of pollinosis among salesmen in multivariate analyses. We observed that other occupational exposures were not associated with the onset of cedar pollinosis after adjusting by covariates, except for a decreased risk of cedar pollinosis for woodworking in men.

Conclusions: These data suggest that exposures related to farming environment might be protective against cedar pollinosis.