Risk factors for mortality in hospitalized COVID-19 patients across five waves in Pakistan

This retrospective cohort study aims to describe the clinical characteristics and outcomes and assess risk factors for mortality across the epidemic waves in hospitalized COVID-19 patients in a major tertiary-care center in Pakistan. A total of 5368 patients with COVID-19, hospitalized between March 2020 and April 2022 were included. The median age was 58 years (IQR: 44–69), 41% were females, and the overall mortality was 12%. Comparative analysis of COVID-19 waves showed that the proportion of patients aged ≥ 60 years was highest during the post-wave 4 period (61.4%) and Wave 4 (Delta) (50%) (p < 0.001). Male predominance decreased from 65.2% in Wave 2 to 44.2% in Wave 5 (Omicron) (p < 0.001). Mortality rate was lowest at 9.4% in wave 5 and highest at 21.6% in the post-wave 4 period (p = 0.041). In multivariable analysis for risk factors of mortality, acute respiratory distress syndrome (ARDS) was most strongly associated with mortality (aOR 22.98, 95% CI 15.28–34.55, p < 0.001), followed by need for mechanical ventilation (aOR 6.81, 95% CI 5.13–9.05, p < 0.001). Other significant risk factors included acute kidney injury (aOR 3.05, 95% CI 2.38–3.91, p < 0.001), stroke (aOR 2.40, 95% CI 1.26–4.60, p = 0.008), pulmonary embolism (OR 2.07, 95% CI 1.28–3.35, p = 0.003), and age ≥ 60 years (aOR 2.45, 95% CI 1.95–3.09, p < 0.001). Enoxaparin use was associated with lower mortality odds (aOR 0.45, 95% CI 0.35–0.60, p < 0.001. Patients hospitalized during Wave 4 (aOR 2.22, 95% CI 1.39–3.56, p < 0.001) and the post-wave 4 period (aOR 2.82, 95% CI 1.37–5.80, p = 0.005) had higher mortality odds compared to other waves. The study identifies higher mortality risk in patients admitted in Delta wave and post-wave, aged ≥ 60 years, and with respiratory and renal complications, and lower risk with anticoagulation during COVID-19 waves.