Trends of in-hospital and ICU mortality in COVID-19 patients over the fourth and fifth COVID-19 surges in Iran: a retrospective cohort study from Iran

Abstract Objective The current study aimed to investigate the temporal trend of in-hospital and intensive care unit (ICU) mortality of coronavirus disease 2019 (COVID-19) patients over 6 months in the spring and summer of 2021 in Iran. Design We performed an observational retrospective cohort study. Setting Qazvin Province- Iran during 6 month from April to September 2021. Participants All 14355 patients who were hospitalized with confirmed COVID-19 in hospitals of Qazvin Province. Intervention No intervention. Main outcome measures The trends of overall in-hospital mortality and ICU mortality were the main outcome of interest. We obtained crude and adjusted in-hospital and ICU mortality rates for each month of admission and over surge and lull periods of the disease. Results The overall in-hospital mortality, early mortality and ICU mortality were 8.8%, 3.2% and 67.6%, respectively. The trend for overall mortality was almost plateau ranging from 6.5% in July to 10.7% in April. The lowest ICU mortality was 60.0% observed in April, whereas it reached a peak in August (ICU mortality = 75.7%). Admission on surge days of COVID-19 was associated with an increased risk of overall mortality (Odds ratio = 1.3, 95% confidence interval = 1.1, 1.5). The comparison of surge and lull status showed that the odds of ICU mortality in the surge of COVID-19 was 1.7 higher than in the lull period (P-value