Risk factors for lung cancer in Iowa women: implications for prevention

Abstract

Background: Multiple risk factors possibly associated with lung cancer were examined as part of a large-scale residential radon case-control study conducted in Iowa between 1994 and 1997. We were particularly interested in stratifying risk factors by smoking status. Relatively little risk factor information is available for Midwestern rural women.

Methods: Four hundred thirteen female lung cancer cases and 614 controls aged 40-84, who were residents of their current home for at least 20 years, were included. Risk factors examined included cigarette smoking, passive smoking, occupation, chemical exposure, previous lung disease, family history of cancer, and urban residence. Multiple logistic regression analysis was conducted after adjusting for age, education, and cumulative radon exposure.

Results: As expected, active cigarette smoking was the major risk factor for lung cancer. While cessation of smoking was significantly associated with a reduced risk for lung cancer, the risk remained significantly elevated for 25 years. Among all cases, asbestos exposure was a significant risk. Among ex-smokers, pack-year history predominated as the major risk. Among never smokers, a family history of kidney or bladder cancer were significant risk factors (OR=7.34, 95% CI=1.91-28.18; and OR=5.02, 95% CI=1.64-15.39, respectively), as was a history of previous lung disease (OR=2.28, 95% CI=1.24-4.18) and asbestos exposure. No statistically significant increase in lung cancer risk was found for occupation or urban residence.

Conclusions: Smoking prevention activities are urgently needed in rural areas of the United States. Relatives of individuals with smoking-related cancers are potentially at increased risk. Genetic risk factors should be more fully investigated in never smokers.

Fig. 1

Lung Cancer Risk Associated with Cigarette Use. Estimates of the lung cancer odds ratio associated with cigarette pack- year exposure. The dashed lines represent 95 percent pointwise confidence intervals. This figure is based on a model adjusting for radon (WLM 20), education (some college), and years since quitting smoking (maximum of 25 years). Comparison is made to never smokers.

Fig. 2

Lung Cancer Risk Subsequent to Smoking Cessation. Estimates of the lung cancer odds ratio associated with years since smoking cessation (maximum of 25 years) (smkquit) among current and ex-smokers. The dashed lines represent 95 percent pointwise confidence intervals. This figure is based on a model adjusting for radon (WLM 20), education (some college), age, and pack-years. Comparison is made to current smokers.