Cancer incidence among women living on farms: findings from the Iowa Women's Health Study.

The purpose of this study was to determine whether site-specific cancer incidence in women residing on farms is different from those residing elsewhere. A large population-based cohort of Iowa women 55 to 69 years of age reported in a questionnaire whether or not they lived on a farm. Linkage to a statewide registry identified cancers occurring between 1986 and 1992. Age-adjusted relative risks (RR; 95% confidence interval) of all cancers (RR = 0.84; 0.76 to 0.92), lung cancer (RR = 0.32; 0.20 to 0.50), and bladder cancer (RR = 0.33; 0.12 to 0.92) were reduced significantly in farm residents, compared with non-farm residents. These findings were largely accounted for by other cancer risk factors, most importantly, cigarette smoking. The multivariate adjusted risk of non-Hodgkin's lymphoma was elevated in farm residents for all lymphoma sites (RR = 1.52; 0.96 to 2.39) and lymph node sites (RR = 1.89; 1.13 to 3.18). Reduced risks of smoking-related cancers and elevated risk of non-Hodgkin's lymphoma among farm residents have been reported previously, primarily in men. Our findings suggest that farm women may be exposed to some of the same factors that determine cancer risk in male farmers.