3.1. Basic characteristics
The median age of the study population (n=12,817) was 44 (25) years, and 50.9% was female. The demographic and clinical parameters of the three groups are displayed in Table 1. The percentage (number) of patients in group-1, 2, and 3 were 46.1% (n=5911), 47.3% (n=6058), and 6.6% (n=848), respectively. Median age, male sex, and mean BMI showed increases from group 1 to group 3. The current smoking rates in the groups were 21.2%, 19.1%, and 22.4%, respectively.
As shown in Table 1, most laboratory test results showed a significantly worse direction from group-1 to group-3. Notably, D-dimer, CRP, LDH, ferritin, and lymphopenia that were more commonly referred to COVID-19 severity, increased gradually across the groups. Only three laboratory variables, total cholesterol, LDL-cholesterol, and fibrinogen, were not different from normal glucose to high glucose group. Lung involvement on CT increased considerably from group-1 to group-3.
The prevalences of hypertension, dyslipidemia, obesity, asthma/COPD, heart failure, CVD, chronic kidney disease, and cancer were significantly different among the three groups, with more than double the increase in the frequencies of CVD, heart failure, chronic kidney disease, and medications in group 3 (Table 1). Similarly, the use of RAS blockers, statins, and acetylsalicylic acid (ASA) was more common in group-3.
3.2. Outcome analysis
There were significant differences in the primary and secondary outcomes across the groups. Mortality rate was found to be 14% in group-3, which was significantly higher than the mortality rate of 5% and 2.1% in group-2 and group-1, respectively. Mortality was also significantly higher in group-2 compared to group-1. Similar differences were also found in the rate of hospitalization, hospital stays longer than the median duration (8 days), ICU admission, ICU stay longer than the median duration (6 days), and mechanical ventilation (Table 2).
3.3. Independent associations of mortality and secondary outcomes
Multivariate analyses indicated that age (OR, 95% CI: 1.02, 1.01-1.02), lung involvement (OR, 95% CI: 3.12, 2.58-3.77), lymphopenia (OR, 95% CI: 1.26, 1.03-1.55), chronic kidney disease (OR, 95% CI: 1.62, 1.12-2.33), cancer (OR, 95% CI:1.49, 1.02-2.18) and the use of ASA (OR, 95% CI: 1.68, 1.24-2.27) were associated with the risk of hospitalization (Table 3). Additionally, age (OR, 95% CI: 1.07, 1.06-1.09), male gender (OR, 95% CI: 2.68, 1.73-4.15), lung involvement (OR, 95% CI: 1.55, 1.04-2.32), glucose levels in the range of 140-199 mg/dl (OR, 95% CI: 2.66, 1.41-5.00), lymphopenia (OR, 95% CI: 1.1.87, 1.25-2.80), CRP (OR, 95% CI: 3.11, 1.69-5.73), hypertension (OR, 95% CI:1.95, 1.00-3.79) and chronic kidney disease (OR, 95% CI:2.16, 1.40-3.35) associated with mortality (Table 2). Also, age (OR, 95% CI: 1.04, 1.03-1.05), male gender (OR, 95% CI: 1.92, 1.46-2.53), lung involvement (OR, 95% CI: 1.63, 1.25-2.13), glucose level in the range of 140-199 mg/dl (OR, 95% CI: 2.26, 1.45-3.52), lymphopenia (OR, 95% CI:2.03, 1.54-2.66), CRP (OR, 95% CI: 2.31, 1.67-3.20) and heart failure (OR, 95% CI: 1.94, 1.26-2.98) were significantly associated with the composite of ICU admission and/or mechanical ventilation (Table 2).
The Kaplan-Meier graph of 30-day mortality curves in the total sample is given in Figure 2. The rate of mortality in group 3 patients was significantly higher (Log-Rank test: p<0.001) than in other groups.