Association between the Leukemia Mortality-to-Incidence Ratio and State Geographic Healthcare Disparities in the United States


INTRODUCTION: Leukemia is the seventh leading cause of cancer death in the United States (US) in 2021. The Mortality Incidence Rate Ratio, also known as Mortality-to-Incidence Ratio (MIR), is calculated by dividing the mortality rate by the incidence rate for selected cancers and population. The MIR provides a population-based indicator of cancer survival which has previously been used to assess healthcare disparities among different countries. Here weevaluated the potential association between leukemia MIR and state-based health disparities in the US.

METHODS: Leukemia (AML, CML, ALL, CLL and other leukemias) MIRs for 2008-2017 were obtained from United States Cancer Statistics (USCS) database provided by the Centers for Disease Control and Prevention (CDC). America’s Health Rankings (AHR), a partnership of the United Health Foundation and the American Public Health Association, evaluates the nation’s health on a state-by-state basis by using weighted measures in 5 different categories (25% for Behaviors, 22.5% for Community & Environment, 12.5% for Policy, 15% for Clinical Care, and 25% for Outcomes). AHR then determines state health rankings and reflects state health disparities based on these specific factors. Here we analyzed the potential association between leukemia MIRs and state health rankings by linear regression.

RESULTS: From 2008 to 2017, a total of 489,037 people were diagnosed with leukemia and 231,069 people died from leukemia in the US. The 10-year average of age-adjusted incidence rate and mortality rate were 14.2 and 6.7 per 100,000 population respectively. The average MIR between all states was calculated to be 0.470. As seen in Table 1, the lowest MIR (best survival) was found in Florida (0.374), New York (0.391), and New Jersey (0.412) with AHR 34, 19 and 11 respectively. The highest MIR (worst survival) was found in Mississippi (0.579), Wyoming (0.570), and Ohio (0.569) with AHR 50, 24 and 37 respectively. According to AHR, over the last decade, the states with the highest health rankings were reported in Vermont (No. 1), Hawaii (No. 2), and Massachusetts (No. 3) with MIR 0.508, 0.439 and 0.502 respectively. The states with the lowest health rankings were reported in Arkansas (No. 48), Louisiana (No. 49), and Mississippi (No. 50) with MIR 0.559, 0.503 and 0.579 respectively. In our analysis, states with better health rankings were significantly associated with lower MIRs (R2=0.232, P<0.001), as seen in Figure 1.

CONCLUSIONS: There is a remarkable geographic difference in leukemia MIRs in the US between 2008-2017. Leukemia MIR was significantly associated with state health rankings reported by the AHR. Although the quality of clinical care for leukemia patients remains to be an important predictor of mortality, our findings suggest that other aggregate determinants of health, including social, economic, and community and physical environment may also play a vital role in influencing leukemia survival. More in-depth analysis of these data focusing on specific leukemia subtypes as well as other factors (race, gender, age) may be helpful in identifying and addressing other non-medical issues negativity impacting on leukemia outcomes in different geographical regions in the United States.