Economic vulnerability or social inequality? A global comparative analysis of their relative impact on chronic kidney disease burden.

PURPOSE: To compare the impacts of persistent social inequality (Palma ratio) and conjunctural economic vulnerability (unemployment) on chronic kidney disease (CKD) burden and to test whether hypertension mediates inequality's association.

METHODS

We analyzed a 68-country panel (1990-2023), modeling the natural log of prevalent CKD cases as a function of the Palma ratio and total unemployment, adjusting for diabetes prevalence, hypertension prevalence, hospital beds per 10,000, and population size. Pooled OLS with HC3 robust standard errors was estimated across lags up to 10 years. To reduce detection bias, we re-estimated models at the 10-year lag within wage-defined income strata; mediation (1,000 bootstraps) was assessed in the high-income stratum.

RESULTS

In high-income countries (18 countries, N = 265 observations at the 10-year lag), social inequality was strongly positively associated with the log of total prevalent CKD cases (β = 2.02, 95% CI: 1.32-2.72, p < 0.001), implying that a 1-SD increase in the Palma ratio is associated with a 7.54-fold higher CKD case burden (≈ + 654%), holding covariates constant. Economic vulnerability showed no significant association (β = 0.01, p = 0.871), yielding a 202:1 absolute effect-size ratio. Bootstrap causal mediation indicated a large hypertension pathway (indirect effect = 0.82, 95% CI: 0.34-1.28), corresponding to 78.1% of the total effect. Panel Granger tests suggested that past inequality predicts CKD across tested lags (p < 0.001).

CONCLUSION

We conclude that inequality is the stronger and more consistent upstream determinant of CKD burden, while the effect of unemployment is weaker. The conducted analysis suggests that structural social inequality, quantified by the Palma ratio, has a significantly stronger and more statistically robust correlation with the prevalence of chronic kidney disease compared to economic vulnerability of a conjunctural nature, quantified by the unemployment rate, especially in contexts characterized by adequate diagnostic capacity.