- In models 1–4, the direct relationship between outcome and explanatory variables/potential predictors of each level was presented without adjusting the variables from other levels. Model 5 included the smoking variable along with the age variable as covariate. Model 6 included at least one co-morbid condition with the covariates smoking, and age variables. Model 7 included intensive care unit (ICU) admission, difficulty breathing, and length of hospital stay in days variables, along with the covariates at least one co-morbid conditions, age, and smoking variables
