Differential Temporal Changes in Cerebrovascular Hospitalizations During the COVID-19 Pandemic: An Ecological Time-Series Study in the Municipality of São Paulo, Brazil

Background: The COVID-19 pandemic simultaneously affected vascular risk and healthcare utilization. We evaluated whether monthly trajectories of Brazilian Unified Health System (Sistema Único de Saúde; SUS)-financed hospitalizations for different cerebrovascular categories changed differently during the pandemic in the municipality of São Paulo. Methods: We conducted an ecological time-series study using monthly Hospital Information System of the Brazilian Unified Health System (SIH-SUS), Department of Informatics of the Unified Health System (DATASUS) data from January 2017 through December 2021. Nontraumatic intracranial hemorrhage (I60–I62), cerebral infarction (I63), unspecified stroke (I64), and other cerebrovascular diseases (I65–I69) were included. The analytical dataset comprised 240 monthly observations. Annual IBGE population estimates were used as denominators. The primary analysis used segmented negative-binomial regression with log(population) offset, temporal trend, an immediate level change from March 2020, post-intervention slope change, and annual harmonic terms for seasonality. Poisson and negative-binomial models were compared using overdispersion diagnostics and Akaike information criterion (AIC). Residual autocorrelation, category-by-intervention interactions, alternative intervention dates, and leave-one-month-out influence were assessed. Results: A total of 60,756 hospitalizations were identified. Descriptive differences in mean annual counts between the pre-pandemic and pandemic periods were +3.7% for intracranial hemorrhage, +15.2% for cerebral infarction, −16.2% for unspecified stroke, and −27.2% for other cerebrovascular diseases. All categories were overdispersed (Pearson ratios 2.16–5.05), and AIC was consistently lower for negative-binomial models. In the primary segmented model, March 2020 was associated with an immediate 39.3% decrease in other cerebrovascular diseases (incidence rate ratio [IRR] 0.607; 95% confidence interval [CI] 0.512–0.720; p < 0.001) and a 10.0% decrease in unspecified stroke (IRR 0.900; 95% CI 0.817–0.991; p = 0.032). No statistically significant immediate level change was found for intracranial hemorrhage (IRR 1.018; p = 0.760) or cerebral infarction (IRR 0.868; p = 0.086). No category showed a significant post-intervention slope change. The formal category-by-level-change interaction was significant (Wald p = 0.004), indicating heterogeneity among categories. LjungBox tests at 12 lags showed no significant residual autocorrelation. Conclusions: SUS-financed cerebrovascular hospitalizations showed heterogeneous temporal changes during the pandemic, particularly immediate decreases in I64 and I65–I69. The findings support differences in trajectories across diagnostic categories but do not demonstrate diagnostic migration, individual biological mechanisms, or causality. Changes in care-seeking, referral, coding, diagnostic availability, and healthcare organization remain plausible but untested explanations.