Do the associations between cigarette smoking and the risk of dying from tobacco-associated malignancies differ by race?

B121

Introduction: African Americans suffer disproportionately higher tobacco-related cancer incidence and mortality rates compared to European Americans. This racial disparity cannot fully be explained by differences in patterns of cigarette smoking prevalence between the two populations. One potential explanation is that smoking is a stronger risk factor for cancer in African Americans than European Americans. To test this hypothesis, we assessed whether the association between smoking and risk of death from tobacco-related malignancies was greater among African Americans than among European Americans.
 >Methods: We pooled data from the Evans County Heart Study and the Charleston Heart Study, each cohort study having a minimum follow-up period of 30 years. When pooled across cohorts, the resulting sample was comprised of 5,363 participants, 38% of whom were African American. There were a total of 296 deaths from tobacco-related malignancies and 170 deaths from lung cancer. Tobacco-related malignancies included cancers of the lung, esophagus, pancreas, oral cavity, bladder, larynx, kidney, stomach, acute myeloid leukemia, and uterine cervix. Analyses were performed for all tobacco-related malignancies combined and for lung cancer separately. All hazards ratio estimates come from a competing risks Cox proportional hazards model adjusted for age, years of education, body mass index, and hypertension.
 >Results: For all tobacco-related malignancies combined, African American men had a statistically significantly (p = 0.04) lower smoking-related risk of death (Hazards Ratio (HR) 2.2; 95% Confidence Interval (CI) 1.2-3.8) than European American men (HR 5.4; 95% CI 3.4-8.7). The same held true for women, with African American women having a statistically significantly (p < 0.01) lower smoking-related risk of death from tobacco-related malignancies (HR 1.5; 95% CI 0.6-3.6) than European American women (HR 6.5; 95% CI 3.7-11.2). In contrast, the results for lung cancer showed that African American men had a higher smoking-related risk of death (HR 10.7; 95% CI 2.5-45.3) than European American men (HR 6.8; 95% CI 3.7-12.5), a difference that was not statistically significant (p = 0.40). This result was not replicated in women, as African American women had a nonsignificantly lower smoking-related risk of death from lung cancer than European American women (p = 0.09).
 >Conclusions: Contrary to expectation, the associations between cigarette smoking and death from tobacco-related malignancies were actually higher in European Americans than African Americans in this study. The results hinted that cigarette smoking may contribute to the racial disparity in lung cancer death rates among men, but this was not seen in women. The results suggest that differential susceptibility to tobacco-caused carcinogenesis is, by itself, an unlikely cause of excess mortality rates of tobacco-related malignancies in African Americans.