Geographic Patterns in U.S. Lung Cancer Mortality and Cigarette Smoking

BACKGROUND: Despite the success of smoking cessation campaigns, lung cancer remains the leading cause of cancer death in the U.S. Variations in smoking behavior and lung cancer mortality are evident by sex and region. METHODS: Applying geospatial methods to lung cancer mortality data from the National Vital Statistics System and county-level estimates of smoking prevalences from the NCI's Small Area Estimates of Cancer-Related Measures, we evaluated patterns in lung cancer mortality rates (2005-2018) in relation to patterns in ever cigarette smoking prevalences (1997-2003). RESULTS: Overall, ever smoking spatial patterns were generally associated with lung cancer mortality rates, which were elevated in the Appalachian region and lower in the West for both sexes. However, we also observed geographic variation in mortality rates that is not explained by smoking. Using Lee's L statistic for assessing bivariate spatial association, we identified counties where the ever smoking prevalence was low and lung cancer rates were high. We observed a significant cluster of counties (n = 25; P values ranging from 0.001 to 0.04) with low ever smoking prevalence and high mortality rates among females around the Mississippi River region south of St. Louis, Missouri and a similar and smaller cluster among males in Western Mississippi (n = 12; P values ranging from 0.002 to 0.03) that has not been previously described. CONCLUSIONS: Our analyses identified U.S. counties where factors other than smoking may be driving lung cancer mortality. IMPACT: These novel findings highlight areas where investigation of environmental and other risk factors for lung cancer is needed.