Hospitalisations in Brazil: an ecological time series analysis of the impact of medical decision support data as an exogenous variable

Public health surveillance depends on continuous monitoring to guide interventions and allocate resources effectively. This study aimed to evaluate whether structured medical search data from the Afya Whitebook®, a clinical decision-support platform, can serve as exogenous variables to enhance the explanatory capacity of time series models characterising hospitalisation patterns within Brazil's public health system. An ecological time series analysis was conducted using hospitalisation data (SIH/SUS) and Afya Whitebook® search volumes from 2021 to 2024. SARIMAX models assessed temporal associations between search activity and hospital admissions across Brazilian states, compared to univariate SARIMA models to evaluate the added value of search data. In 278 of the 478 time series, SARIMAX models provided a better fit than univariate SARIMA models, particularly for conditions such as chronic obstructive pulmonary disease, dengue, urinary tract infections, type 2 diabetes, asthma, depression, and chronic kidney disease. Model fit varied by disease and region, underscoring the influence of contextual factors in the association between search behaviour and hospital admissions. This study demonstrates that structured medical search data can serve as exogenous variables to improve the explanatory capacity of time series models of hospitalisation patterns. Despite variation between diseases and regions, this approach shows promise in supporting public health surveillance and could be strengthened by incorporating contextual data in future studies.