Geographic disparity in systemic sclerosis mortality in the United States: 1999-2017

Introduction: Previous studies reported a progressive decrease in the systemic sclerosis mortality rates in the United States from 1959 to 2002. Identification of areas with clusters of higher mortality rates is important to implement targeted interventions. In this study, we aimed to estimate the mortality rates of scleroderma and to analyze its geographic variability at the state level in the United States. Methods: Mortality rates of scleroderma from 1999 to 2017 were obtained from the CDC Wonder Underlying Cause of Death database and its query system, using International Classification of Diseases, Tenth Revision codes. Age-adjusted rates were calculated by state and demographics. A linear regression model was applied to evaluate trends over time. Results: Over the period studied, a total of 24,525 deaths had scleroderma as the underlying cause of death. The age-adjusted mortality rate was 3.962 per million (95% CI: 3.912-4.012), decreasing progressively from 4.679 (95%CI: 4.423-4.934) in 1999 to 2.993 (95% CI: 2.817-3.170) per million in 2017. The age-adjusted mortality rate was 5.885 (95% CI: 5.802-5.967) and 1.651 (95% CI: 1.604-1.698) per million in females and males, respectively. Per races, the highest age-adjusted mortality rate was in Blacks or African Americans, at 5.703 per million (95% CI: 5.521-5.885), followed by American Indians or Alaska Native at 5.047 per million (95% CI: 4.428-5.667). Clusters of states with higher and lower mortality rates were identified. South Dakota had the highest whereas Hawaii had the lowest mortality rate. Conclusion: We found a trend to a progressive decrease in mortality rates of scleroderma during the years of our study. In addition, we found relevant state-by-state variation in mortality with several geographical clusters with higher mortality rates. Further analyses are warranted in order to better understand the factors associated with the observed geographic disparities.