3.1 General conditions
Approximately 5.16% (37/718) (Table 1, Figure 5A) of patients had severe COVID-19, and 1.11% (8/718) (Table 1, Figure 5B) of severe COVID-19 patients died.
For the distribution characteristics of age, approximately 88.62% (637/718) (Figure 2A) of COVID-19 patients were twenty to fifty-nine years old. A small number of patients were younger than 20 years old or older than 60 years old (Figure 2A).
Patients in each comorbidity subgroup were older than those in the no-comorbidity subgroup (Figure 3), especially those with COPD and CVD (Figure 3). Except for the CKD subgroup and the cancer subgroup, the differences were statistically significant (all P＜0.001).
In this COVID-19 cohort, the order of clinical type according to the number of cases was as follows: common, asymptomatic infection, light, critical illness and severe. The percentages were 51.67%, 32.59%, 10.17%, 2.65%, and 2.51%, respectively (Figure 4B).
Severe cases (critical illness and severe clinical type) were distributed in age-interval subgroups older than twenty years, especially in the subgroup of patients older than seventy years (Figure 5A). Those who died were in the older than sixty age-interval subgroup, especially in those older than seventy (Figure 5B).
3.2 The distribution characteristics of comorbidities in different clinical type groups and different age-interval subgroups
Approximately 65.73% (554/718) (Figure 4A) of COVID-19 patients had one or more comorbidities, and 37.85% (176/718) of patients had two or more comorbidities.
Common comorbidities were NAFLD, hyperlipidaemia, hypertension, DM, CHB, hyperuricaemia and gout (Figure 2B). Cancer, COPD, CVD, CKD and other comorbidities were rare (Figure 2B).
Among COVID-19 patients, hypertension, DM, COPD and CVD were mainly found in patients with the critically ill clinical type (Figure 6A, 6E, 6G, 6I), CKD and CVD were mainly found in patients with the common and severe clinical type (Figure 6H, 6I), and hyperuricaemia and gout (Figure 6B) were mainly found in patients with the common clinical type. NAFLD (Figure 6D) was rare in those with the severe clinical type.
Among COVID-19 patients, hypertension, CHB, COPD and CVD (Figure 7A, 7F, 7G, 7I) were mostly distributed in those aged 50 and 80 years old. Cancer, CKD and other comorbidities (Figure 7H, 7J, 7K) mostly occurred in patients older than 70 years. DM, hyperlipidaemia, hyperuricaemia and gout, and NAFLD (Figure 7B, 7C, 7D, 7E) were mostly distributed in patients aged 20 and 70 years.
3.3 The relationship of comorbidities with disease progression and prognosis in COVID-19 patients
In the severe group, patients were older than those in the non-severe group and had a greater number of comorbidities (Table 2) (all P<0.0001). However, there were no differences in comorbidities between the two groups (Table 2) (P˃0.05).
In the non-surviving group, patients were older than those in the surviving group and had a greater number of comorbidities, more hypertension, more chronic kidney disease and more cardiovascular diseases (Table 3) (all P<0.05). No differences in other comorbidities between the two groups were detected (Table 3) (P˃0.05).
According to Spearman correlation analysis, only the number of comorbidities was correlated positively with disease severity (Table 4), though no specific comorbidity correlated with disease severity (Table 4). Moreover, the number of comorbidities, NAFLD, CHB and COPD were all correlated positively with virus negative conversion time (Table 4), and the number of comorbidities, CKD, CVD and hypertension correlated positively with prognosis (Table 4). While when the age was controlled, according to partial correlation analysis, the number of comorbidities was also correlated positively with disease severity (Table 5), the number of comorbidities and NAFLD were also correlated positively with virus negative conversion time (Table 5), and CKD, CVD and hypertension correlated positively with prognosis (Table 5). But there was no no longer any correlation between CHB, COPD and virus negative conversion time, and between the number of comorbidities and prognosis (Table 5).
According to multiple stepwise regression analysis for disease severity, risk factors included the number of comorbidities and hyperlipidaemia (Table 6). Risk factors for virus negative conversion time were the number of comorbidities, hyperlipidaemia, NAFLD and COPD (Table 6). Furthermore, risk factors for prognosis were the number of comorbidities and CKD (Table 6).
3.4 The prediction of number of comorbidities on disease progression and the outcomes of COVID-19 patients
According to the ROC analysis, number of comorbidities could predict disease progression and patient outcomes (Table 7, 8). The best cutoff point for distinguishing the severe cases from the non-severe cases was more than three comorbidities (Table 7). Its area under the curve was 0.864, (Table 7, Figure 8). Its sensitivity was 75.70% (Table 7). Its specificity was 88.00% (Table 7). The best cutoff point for distinguishing the dead cases from the survival cases was more than four comorbidities (Table 8). Its area under the curve was 0.947, (Table 8, Figure 9). Its sensitivity was 85.70% (Table 8). Its specificity was 91.60% (Table 8).