Demographic and clinical characteristics
Ages ranged from 18 to 88 y with a median of 44 y (IQR 34-54), and half of participants were male (Supplement Figure 1). Half of patients were in the 30-50-y age groups (Supplement Figure 1). Height was decreased significantly decreased with older age (p = 0.001), but BMI was not significantly different among groups.
One-third of participants had one or more chronic disease. The total number of chronic diseases differed significantly (p < 0.001) between age groups, with elderly have more chronic disease. Older age groups had more patients with at least one or more chronic disease (5%, 16%, 34%, 52% and 75% in <30, 30-40, 40-50, 50-65 and ≥65 age groups, respectively; p < 0.001). Older age groups had higher prevalences of DM history (p < 0.001) and hypertension history (p < 0.001), chronic heart disease history (p=0.013), and chronic pulmonary disease history (p=0.011). There was no significant difference in prevalences of history of cancer, chronic nervous system disease, chronic liver and kidney disease, endocrine and immune disease among the age groups. Prevalence of bilateral radiographic pneumonia findings was high in all five age groups (overall, 79%) and was increasedsignificantly with older age (61%, 73%, 82%, 86% and 90% in<30, 30-40, 40-50, 50-65 and ≥65 age groups, respectively; p = 0.005). 71(23.75%) patients could not provide a definite contact or exposure history with confirmed or suspected COVID-19 infection. 53.33% of 30-40 years and 50% of 40-50 years were imported cases, and none of the elderly were imported cases. Percentage of secondary cases were 55% among elderly, 42.03% in 50-65 years and 43.9% in<30 years. Temperature, heart rate, respiratory rate on admission were slightly increased in older age groups (Table 1).
Symptoms
The most common symptoms were cough in 216 (72%) patients, fever in 202 (68%), expectoration in 139 (46%), fatigue in 117 (39%), dry cough in 77 (26%) and were of comparable prevalence in all age groups. Only dyspnea was significantly different between elderly group and other groups (p=0.001) (Supplement Figure 2a).
Comparison of laboratory testing profile
Hemoglobin (Hb) and albumen levels (Supplement Table 1) fell with increasing age: Hb 146,140,141,126 and 122g/l in<30, 30-40, 40-50, 50-65 and ≥65 y age groups, respectively; p = 0.000; and albumin 42.25, 45.36,45.36, 42.6, 40.9 and 36.92 g/l in<30, 30-40, 40-50, 50-65 and ≥65 age groups, respectively; p = 0.000).
Patients age ≥65 had significantly higher neutrophil percentage compared to age<30 (69.25% vs. 57.8%, p=0.002). Age ≥65 had significant lower lymphocyte percentage compared to age<30 and age 30-40 (19.25 vs. 32.75, p=0.003; 19.25 vs. 29.1, p=0.015). Age<30 had significantly higher levels of lymphocyte counts compared to age 30-40, 40-50, 50-65, ≥65 (1.6 vs. 1.2, p = 0.009; 1.6 vs. 1.15, p = 0.002; 1.6 vs. 1.29, p = 0.021; 1.6 vs. 1.06, p < 0.001). The level of ESR and PCT of age ≥65 were the highest among all groups; these values were higher than level of ESR and PCT of age<30, 30-40, 40-50 and 50-65 with statistically significant differences (p < 0.001). Age ≥65 had significantly higher levels of CRP compared to age 30-40 (13.9 vs. 0.5, p = 0.002). The increased inflammation as reflected by increased ESR and PCT and decreased immune function as reflected by decreased lymphocyte counts suggesting that there may be more inflammatory factor storm and immune dysfunction with increasing age groups.
Measurements such as BUN (5.12 vs. 3.82, p = 0.008; 5.12 vs. 3.7, p = 0.001; 5.12 vs. 3.7, p = 0.018) and Mb (86.25 vs. 37.35, p = 0.006; 86.25 vs. 35, p = 0.007; 86.25 vs. 33.5, p = 0.004) of age ≥65 were significantly higher than those of age<30, 30-40 and 40-50.
In addition, levels of DD of age ≥65 was significantly higher than those of age<30, 30-40 and 40-50 and 50-65 (0.66 vs. 0.29, p < 0.001; 0.66 vs. 0.28, p < 0.001; 0.66 vs. 0.31, p< 0.001; 0.66 vs. 0.35, p < 0.001). Levels of platelets of age ≥65 and 50-65 was significantly lower than those of age<30 (175.5 vs. 245, p=0.037; 184 vs. 245, p = 0.019) (Supplement Table 1 and Figure 1). These changes suggesting potentially heart, kidney and coagulation function damage in the oldest age group. The levels of WBC, N, PT time, APTT, AST, CK, CKMB, TBIL, K, Na, Cr, LDH, and Glu of the groups were not statistically different among different age groups.
Medical treatments and outcomes of COVID-19 among the age groups
80% received Interferon alpha inhalation (239/299), 76% of the patients received Lopinavir/ritonavir (228/299), 57% received Arbidol (169/299), and 65.22% received Lianhua Qingwen Capsule treatment (chinese medicine). Combination use of Arbidol, Lopinavir/ritonavir or Interferon alpha inhalation was also common. Empirical antibiotic treatment was used when bacterial infection was suspected, which may reference for elevated Neu, PCT value and sputum. 42% were received antibiotic (126/299). Percentage of corticosteroid (17/57, 43%) and gamma globulin (19/56, 48%) treatment was highest in age ≥65.
In particular, mild type accounted for 10.7% (32/299), moderate type accounted for 77.26% (75/299), severe type accounted for 8.7% (10/299), critical type accounted for 3.34% (4/299). Proportion of severe or critical type was 2.44%, 5.33%, 9.46%, 14.49%, and 35% in patients with age<30, 30-40, 40-50, 50-65, ≥65, respectively (p < 0.001). Proportion of mild or moderate type was 97.56%, 94.67%, 90.54%, 85.51%, and 65% in patients with age<30 30-40, 40-50, 50-65, ≥65. The medium time from onset treatment to throat swab turn negative was 15.5 days in age ≥65, 16 days in age 50-65, and 11 days in age<30, 10 days in 30-40, 11.5 days in 40-50.
At this point, ICU admission rate was 0%, 4%, 3%, 4% and 18% in age<30, 30-40, 40-50, 50-65, ≥65 (p = 0.003). ARDS rate was 0%, 4%, 7%, 9% and 30% in age<30, 30-40, 40-50, 50-65, ≥65 (p < 0.001). Rate of shock was 0%, 1%, 1%, 0% and 10% in age<30, 30-40, 40-50, 50-65, ≥65 (p = 0.006). 285 patients (95.32%) were cured and discharged, 12 patients (4.01%) was still on medical treatment in hospital, 2 patients (0.67%) died because of respiratory failure (p < 0.001). On medical treatment rate was 0%,1.33%, 2.7%,2.9% and 17.5% in age<30, 30-40, 40-50, 50-65, ≥65. There were no difference in time from symptom onset to initial treatment and hospitalization days among age groups (Supplement Table 1).
Comparison of clinical characteristics of COVID-19 between mild/moderate type and severe/critical type
Patients developed to severe or critical type were older than patients with mild or moderate type (57.72 vs. 44.06 p = 0.002). Comparison were performed to determine factors associated with severe or critical type in overall COVID-19 patients. Patients developed to severe or critical type have higher percentage of cough (94.44% vs. 69.2%, p = 0.004), fever (88.89% vs. 64.64%, p = 0.002), expectoration (63.89% vs. 44.11%, p = 0.026), fatigue (61.11% vs. 36.12%, p = 0.004), dyspnea (58.33% vs. 8.37%, p < 0.001), and hemoptysis (8.33% vs. 0.76%, p = 0.014) symptom than patients with mild or moderate type (Supplement Figure 2b).
In general, patients developed to severe or critical type have higher percentage with at least one chronic disease (77.78% vs. 29.28%, p < 0.001), DM (30.56% vs. 9.13%, p = 0.001), chronic heart disease (22.22% vs. 2.28%, p < 0.001) and chronic pulmonary disease (16.67% vs. 4.18%, p = 0.009) compared to patients with mild or moderate type. Imported and secondary case accounts for 40.68% and 38.40% in patients with mild or moderate type, however, this proportion was 27.78% and 27.78% in severe or critical type. Noticing that 44.44% of severe or critical type was infected with unknown origin of infected.
Besides, relatively high percent of drugs was prescribed in severe or critical type than mild or moderate type. Obviously, severe or critical type have longer hospitalization days (20.89 vs.17.18, p = 0.011), higher rate of ICU admission (25% vs. 2.28%, p < 0.001), ARDS (52.78% vs. 2.66%, p < 0.001), and shock (13.89% vs.0.38%, p < 0.001) than mild or moderate type. Still on medical treatment rate was 19.44% in severe or critical type and 3.07% in mild or moderate type. In-hospital death cases were 2 in severe or critical type and none in mild or moderate type. However, there was no significant difference regarding sex, BMI, temperature in admission, bilateral involvement on chest radiographs, other onset symptoms and time from symptom onset to initial treatment and time from onset treatment to throat swab turn negative between severe or critical type and mild or moderate type (Table 3).
Factors for severe or critical type in COVID-19 patients
In a binary logistic regression analysis, eight factors (age, HR in admission, R in admission, history of DM, HBP, chronic heart disease, chronic lung disease, epidemiological history) were included as covariates. We found old age (OR 1.055, 95% CI 1.016-1.095, p = 0.006), HR in admission (OR 1.085, 95% CI 1.03-1.144, p = 0.002), R in admission (OR 1.635, 95% CI 1.093-2.431, p = 0.017), and history of chronic heart disease (OR 56.038, 95% CI 2.764-1136.053, p = 0.009) showed independent associations with severe or critical type (Table 4).