Statistical Analysis
Statistical analysis was performed by STATA software version 14 (StataCorp, Texan, USA). All included patients stratified as they received atorvastatin or not during hospitalization. The parametric or non-parametric distribution of the quantitative data was analyzed using the Kolmogorov-Smirnov test. Data description of parametric quantitative variables reported as means ± standard deviation and non-normally distributed data reported as median (interquartile range=IQR). Qualitative variables reported as frequency (percentage). Continues variables compared using independent t-test or Mann-Whitney U test for normally and non-normally distributed data in bivariate analysis, respectively. Categorical variables analyzed using Chi-square or Fisher’s exact test (in the situation in which more than 25% of the categories had frequencies below five). A P-value of less than 0.05 is considered significant.
The crude association between atorvastatin administration and occurrence of outcomes including the need for invasive mechanical ventilation and in-hospital mortality was performed using the univariate COX proportional hazards regression model. For the selection of the best predictors, variables with a P-value of less than 0.2are considered to be analyzed in multivariable COX regression analysis using a stepwise selection approach. Confounders were selected based on the recommendation of previously published epidemiological studies that reported the probable prognostic value of underlying conditions and also medications that were being used 16. This included age, gender, body mass index (BMI) in demographics, hypertension, diabetes mellitus, coronary artery disease, chronic respiratory conditions, malignancies, immunocompromised, chronic kidney disease in comorbidities. Also, we adjusted the model for using beta-blockers and ACEIs or ARBs 17,18. the model was adjusted for the medications which were used to treat COVID-19. Patients with negative time to event removed from the analysis. A 95% confident interval of hazard ratio was reported. The proportional hazard assumption for COX analysis was tested using scaled Schoenfeld residuals and the P-value of 0.05 or more considered as no serious violations of the proportional hazards assumption.