Social determinants, their relationship with leprosy risk and temporal trends in a tri-border region in Latin America

Abstract

Background: Brazil is the only country in Latin America that has adopted a national health system. This causes differences in access to health among Latin American countries and induces noticeable migration to Brazilian regions to seek healthcare. This phenomenon has led to difficulties in the control and elimination of diseases related to poverty, such as leprosy. The aim of this study was to evaluate social determinants and their relationship with the risk of leprosy, as well as to examine the temporal trend of its occurrence in a Brazilian municipality located on the tri-border area between Brazil, Paraguay and Argentina.

Methods: This ecological study investigated newly-diagnosed cases of leprosy between 2003 and 2015. Exploratory analysis of the data was performed through descriptive statistics. For spatial analysis, geocoding of the data was performed using spatial scan statistic techniques to obtain the Relative Risk (RR) for each census tract, with their respective 95% confidence intervals calculated. The Bivariate Moran I test, Ordinary Least Squares (OLS) and Geographically Weighted Regression (GWR) models were applied to analyze the spatial relationships of social determinants and leprosy risk. The temporal trend of the annual coefficient of new cases was obtained through the Prais-Winsten regression. A standard error of 5% was considered statistically significant (p < 0.05).

Results: Of the 840 new cases identified in the study, there was a predominance of females (n = 427, 50.8%), of white race/color (n = 685, 81.6%), age range 15 to 59 years (n = 624, 74.3%), and incomplete elementary education (n = 504, 60.0%). The results obtained from multivariate analysis revealed that the proportion of households with monthly nominal household income per capita greater than 1 minimum wage (β = 0.025, p = 0.036) and people of brown race (β = -0.101, p = 0.024) were statistically-significantly associated with risk of illness due to leprosy. These results also confirmed that social determinants and risk of leprosy were significantly spatially non-stationary. Regarding the temporal trend, a decrease of 4% (95% CI [-0.053, -0.033], p = 0.000) per year was observed in the rate of detection of new cases of leprosy.

Conclusion: The social determinants income and race/color were associated with the risk of leprosy. The study's highlighting of these social determinants can contribute to the development of public policies directed toward the elimination of leprosy in the border region.

Fig 1. Geographic location of the tri-border region of Brazil, Paraguay and Argentina.

Fig 2. Spatial mapping by geographically weighted regression (GWR) of social determinants and their relationship with the risk of leprosy within the tri-border region of Brazil, Paraguay, and Argentina.

(A) Relative Risk, (B) Proportion of households with monthly nominal household income per capita greater than 1 minimum wage (INPC > 1), (C) Proportion of people of brown race (BRACE), (D) R² Adjusted, (E) Coefficients β of proportion of households with monthly nominal household income per capita greater than 1 minimum wage (INPC > 1), (F) Coefficients β of proportion of people of brown race (BRACE).

Fig 3. Temporal evolution of the detection rate of new cases of leprosy in the tri-border region of Brazil, Paraguay and Argentina (2003 to 2015).