In this COVID-19 cohort, the prevalence of severity was 5.16%, and mortality was 1.11%. Most patients with severe disease were older than thirty years, especially older than seventy, and most deaths occurred in those older than seventy years. Overall, age correlated with severity. This finding is consistent with the literature that old age is associated with the progression of COVID-19 and is an independent risk factor for progression  and that advanced age is a risk factor for a worse outcome in association with higher death rates. [16–19]
Approximately 65.73% of the patients in this COVID-19 cohort had one or more comorbidities, and 37.85% had two or more. This is consistent with a report that one-third of patients have no comorbidity according to medical records, but it is lower than the report that 70.7% of patients have one chronic condition and higher than the report that 20.9% patients have 2 or more.  Further analysis found that severe cases had more comorbidities than non-severe cases; those who died had more comorbidities than surviving patients. An increased number of comorbidities correlated positively with disease severity and poor prognosis and was also an independent risk factor for progression and poor prognosis. This was consistent with previous findings that the number of comorbidities is a risk factor for a worse outcome [16–18, 21]
In this study, common comorbidities were mainly NAFLD, hyperlipidaemia, hypertension, DM, CHB, hyperuricaemia and gout; cancer, COPD, CVD, CKD and other comorbidities were not common. The findings are not completely consistent with the report of common comorbidities in hospitalized patients of hypertension, CVD, DM, asthma, COPD, and other underlying diseases, or the systematic review and meta-analysis of 76993 patients that hypertension, CVD, DM, smoking, COPD, malignancy, and CKD, were most prevalent among patients with COVID-19.  We found more types of comorbidities, especially metabolic diseases such as NAFLD, hyperlipidaemia, hyperuricaemia and gout, in our cohort. Moreover, hypertension, DM, COPD, CKD and CVD were mainly present in patients with severe disease who were older than fifty years, especially among those seventy years old. Hypertension, CKD and CVD were common in patients who died and were older than seventy years. These findings were not completely consistent with the literature report that DM and HBP or CVD are common underlying diseases related to death in hospitalized cases,  that COPD increases the risks of death and negative outcomes in patients with severe COVID-19, that impaired renal function is an independent predictor of in-hospital death,  and that risk of death is associated with pre-existing hypertension, diabetes, or chronic kidney disease. 
In this study we found that number of comorbidities played a predictive role in distinguishing severe cases from nonsevere patients and in distinguishing dead cases from surviving cases. More than three and more than four comorbidities predict disease progression, a poor prognosis, respectively.
Based on these findings, advanced age, three or more comorbidities, and some specific comorbidities, such as hypertension, CKD and CVD, are related to progression and death in hospitalized COVID-19 patients.
Our study had several limitations. First, it was a retrospective, single-centre study. Second, the number of severe cases, particularly deaths, was small. Despite these limitations, we report several novel findings: in addition to the common comorbidities reported in the literature, more types of comorbidities, especially metabolic diseases such as NAFLD, hyperlipidaemia and hyperuricaemia, were present in this COVID-19 cohort. Advanced age, two or more comorbidities, and some specific comorbidities, such as hypertension, CKD and CVD, are related to progression and death in hospitalized COVID-19 patients.