Factors associated with prolonged hospitalizations for COVID-19 during the first three waves of the pandemic: Evidence from a Southeastern State of Brazil

A comprehensive understanding of the factors influencing the epidemiological dynamics of COVID-19 across the pandemic waves-particularly in terms of disease severity and mortality-is critical for optimizing healthcare services and prioritizing high-risk populations. Here we aim to analyze the factors associated with short-term and prolonged hospitalization for COVID-19 during the first three pandemic waves. We conducted a retrospective observational study using data from individuals reported in the e-SUS-VS system who were hospitalized for COVID-19 in a state in a southeast state of Brazil. Hospitalization duration was classified as short or prolonged based on a 7-day cutoff, corresponding to the median length of hospital stay during the second pandemic wave. Bivariate analyses were performed using the chi-square test for heterogeneity. Logistic regression models were used to estimate odds ratios (ORs) and their respective 95% confidence intervals (CIs), with statistical significance set at 5%. When analyzing hospitalization duration across the three waves, we found that 51.1% (95%CI: 49.3-53) of hospitalizations in the first wave were prolonged. In contrast, short-duration hospitalizations predominated in the second (54.7%; 95% CI: 52.4-57.0) and third (51.7%; 95% CI: 50.2-53.2) waves. Factors associated with prolonged hospitalization varied by wave. During the first wave, older adults (≥60 years) (OR=1.67; 95%CI: 1.35-2.06), individuals with ≥10 symptoms (OR=2.03; 95%CI: 1.04-3.94), obese individuals (OR=2.0; 95%CI: 1.53-2.74), and those with ≥2 comorbidities (OR=2.22; 95%CI: 1.71-2.89) were more likely to experience prolonged hospitalization. In the second wave, he likelihood of extended hospital stays was higher among individuals aged ≥60 years (OR=2.04; 95%CI: 1.58-2.62) and those with ≥2 comorbidities (OR=1.77; 95%CI: 1.29-2.41). In the third wave, prolonged hospitalization was more frequent among older adults (OR=1.89; 95%CI: 1.65-2.17,), individuals with 5-9 symptoms (OR=1.52; 95%CI: 1.20-1.92), obese individuals (OR=2.2; 95%CI: 1.78-2.73), and those with comorbidities (OR=1.45; 95%CI: 1.22-1.72 and OR=2.0; 95%CI: 1.69-2.45). In conclusion, we identified variations in hospitalization patterns across the pandemic waves, although the differences were relatively subtle. These variations likely reflect gradual shifts in the risk factors associated with prolonged hospital stays. Our findings highlight t the importance of implementing targeted public health interventions, particularly those designed to reduce disease severity and improve clinical outcomes among vulnerable populations at greater risk of extended hospitalization.