Characteristics Associated with COVID-19 Outcomes: A Population-Based Analysis Using SINAEHR® Primary Care Data and Linked Hospital Care Monitoring System

Background: Identifying risk factors for severe COVID-19 outcomes is essential for shaping effective public health strategies. This study analyzed demographic, clinical, and comorbidity-related factors associated with hospitalization, ICU admission, mechanical ventilation, and mortality in a large Iranian population.Methods: We conducted a population-based cross-sectional study of 405,397 individuals registered under the Mashhad University of Medical Sciences, combining primary care records with hospital monitoring data. Variables included age, sex, geographic region, diabetes, hypertension, cardiovascular disease, hyperlipidemia, pregnancy, obesity, and vaccination status. Logistic regression models were applied to examine associations with each outcome.Results: Among 405,397 individuals (mean age 40.21±16 years; 46.30% female), 4.29% were hospitalized, 0.17% admitted to ICU, 0.42% required mechanical ventilation, and 0.67% died. Advanced age (≥80 years) was the strongest predictor across all outcomes, with adjusted odds ratios (AORs) ranging from 17.21 (95% CI, 15.37–19.28) for hospitalization to 283.31 (95% CI, 155.57–515.93) for mortality. Cardiovascular disease, diabetes, obesity, and pregnancy were also significant risk factors. In contrast, female sex (AOR for mortality: 0.63; 95% CI, 0.58– 0.69), hypertension, and hyperlipidemia were associated with reduced risks. Vaccination demonstrated a strong dose-dependent protective effect, with three doses reducing the odds of mortality by 93% (AOR: 0.07; 95% CI, 0.05–0.12).Conclusion: Advanced age, cardiovascular disease, diabetes, obesity, and pregnancy emerged as major risk factors for severe COVID-19 outcomes. The apparent protective associations of female sex, hypertension, and hyperlipidemia warrant further exploration. Most critically, the profound protective effect of vaccination highlights the urgent need to sustain and expand comprehensive immunization programs.