Socioeconomic and cardiometabolic factors associated with outpatient healthcare utilization and direct costs in São Paulo, Brazil

BACKGROUND: The ongoing epidemiological and nutritional transitions impose a significant socioeconomic burden on health systems worldwide. However, evidence integrating population-based biological and lifestyle factors with direct economic valuation in mixed public-private health systems is limited in middle-income countries. Therefore, we analyzed factors associated with outpatient utilization and estimated direct costs (adjusted for International Dollars at Purchasing Power Parity - Int$ PPP) in a representative sample for São Paulo City, Brazil, from 2003 to 2015. METHODS: Pooled cross-sectional observational study, with quantitative analyses of microdata from the São Paulo Health Survey 2003-2015 (ISA-Capital), combined with administrative data from the Brazilian Unified Health System Department of Informatics (SIA-SUS/DATASUS) and the Brazilian Hierarchical Categorization of Medical Procedures (CBHPM). A two-part regression model (logit and generalized linear model) and average marginal effects (ME) were estimated to identify factors associated with the likelihood of utilization and the direct costs of outpatient services. RESULTS: Utilization and costs were higher in more recent survey years. Socioeconomic factors, notably schooling (ME = 13.28, representing a 43.4% relative increase from the sample mean, p < 0.001), showed a stronger statistical association with direct costs than clinical conditions such as high blood pressure (ME = 10.48, 34.2% relative increase, p < 0.001) and overweight (ME = 5.79, 18.9% relative increase, p < 0.001). Female sex (ME = 3.53, 11.5% relative increase, p = 0.004) and private health insurance ownership (ME = 2.99, 9.8% relative increase, p = 0.021) were also positively associated with the outcomes. CONCLUSIONS: Our findings suggest that in the urban context of São Paulo, socioeconomic factors are primarily associated with the outpatient economic burden. Therefore, prioritizing equitable health policies targeting socioeconomically vulnerable groups, aiming to increase outpatient access and utilization, alongside early cardiometabolic risk management, may represent important strategies to strengthen the financial sustainability of Brazil's health system while improving population health.