Our hot spot analysis revealed significant clustering of high and low values for our dependent variable, 5-year lung cancer mortality rate (Figure 5.1), and explanatory variables of interest (Figure 5.2). Five-year lung cancer mortality rates at the county level ranged from 26 to 148 lung cancer deaths per 100,000 people. We found clusters of high lung cancer mortality rates in Tennessee, Kentucky, West Virginia, and Florida. Clusters of low lung cancer mortality rates were observed on the northeastern coast and Michigan, northeastern Illinois, northwestern Ohio and Wisconsin (99% confidence). This output was then directly compared with the outputs of our explanatory variable hot spot analyses (Figure 5.2) to view larger, regional patterns of overlap within our study area.
While there are no apparent hot or cold spots in Florida, our hot spot maps tell a different story in the central and south central Appalachian sub-region, where there are significant hot and cold spots of multiple explanatory variables within the region. First, our analysis identified a significant hot spot of high annual average PM 2.5 concentrations in the area. PM 2.5 is associated with higher rates of lung cancer mortality in North America, which makes this a hot spot of interest as it indicates poorer air quality and subsequently higher risk of lung cancer or respiratory illness (Huang, Pan, Wu, Chen E. & Chen L., 2017). The Central Appalachian region also appears to have the most significant clustering of high smoking prevalence, a definitive link to higher incidence of lung cancer as smoking contributes to 80-90% of lung cancer deaths (Office of the Surgeon General, 2004). The Central Appalachian lung cancer mortality hot spot also coincides with significant cold spots of other explanatory variables. The region has a significantly low proportion of non-white population, low median household incomes and low proportions of university graduates. This aligns with the findings of previous research, emphasizing that the sub-region’s majority white population struggles economically with significantly lower incomes, low educational attainment, high rates of smoking and high lung cancer mortality (CDC, 2002; Halverson & Bischak, 2008; Wingo et al., 2008).