Lung cancer death rates in lifelong nonsmokers

Abstract

Background: Few studies have directly measured the age-, sex-, and race-specific risks of lung cancer incidence and mortality among never tobacco smokers. Such data are needed to quantify the risks associated with smoking and to understand racial and sex disparities and temporal trends that are due to factors other than active smoking.

Methods: We measured age-, sex-, and race-specific rates (per 100,000 person-years at risk) of death from lung cancer among more than 940,000 adults who reported no history of smoking at enrollment in either of two large American Cancer Society Cancer Prevention Study cohorts during 1959-1972 (CPS-I) and 1982-2000 (CPS-II). We compared lung cancer death rates between men and women and between African Americans and whites and analyzed temporal trends in lung cancer death rates among never smokers across the two studies by using directly age-standardized rates as well as Poisson and Cox proportional hazards regression analyses. All statistical tests were two-sided.

Results: The age-standardized lung cancer death rates among never-smoking men and women in CPS-II were 17.1 and 14.7 per 100,000 person-years, respectively. Men who had never smoked had higher age-standardized lung cancer death rates than women in both studies (CPS-I: hazard ratio [HR] = 1.52, 95% confidence interval [CI] = 1.28 to 1.79; CPS-II: HR = 1.21, 95% CI = 1.09 to 1.36). The rate was higher among African American women than white women in CPS-II (HR = 1.43, CI = 1.11 to 1.85). A small temporal increase (CPS-II versus CPS-I) in lung cancer mortality was seen for white women (HR = 1.25, CI = 1.12 to 1.41) and African American women (HR = 1.22, CI = 0.64 to 2.33), but not for white men (HR = 0.89, CI = 0.74 to 1.08). Among white and African American women combined, the temporal increase was statistically significant only among those aged 70-84 years (P < .001).

Conclusions: Contrary to clinical perception, the lung cancer death rate is not higher in female than in male never smokers and shows little evidence of having increased over time in the absence of smoking. Factors that affect the interpretation of lung cancer trends are discussed. Our novel finding that lung cancer mortality is higher among African American than white women never smokers should be confirmed in other studies.