In this retrospective cohort study, logistic regression models were used to identify several independent risk factors for severe cases in inpatients with COVID-19 in Henan province, china. Specifically, age ≥65 years, coexisting diabetes, cough, increased PCT, and LDH greater than 245 U/L on admission were associated with higher odds of severe cases among hospitalized COVID-19 patients.
This study found that age ≥65 years on admission was associated with increased odds of severe cases among hospitalized COVID-19 patients. Severe SARS-CoV-2 infection can occur in any age group, but is most often associated with middle-aged and elderly people. According to a report by The Chinese Center for Disease Control and Prevention, among about 44,500 confirmed infected patients, 87% were between 30 and 79 years old, and older patients were also associated with increased mortality. The fatality rates of patients aged 70–79 and ≥80 years were 8% and 15%, respectively [9]. In the United States, 67% of the cases were diagnosed at the age ≥45, and similar to the cases in China, the elderly had the highest mortality rate with 80% of the patients dying among patients aged ≥65 years [12].The findings of this study were in accord with the above reports. The mechanism by which advanced age leads to severe illness is unclear. Previous studies in macaques inoculated with SARS-CoV found that older macaques had stronger host innate responses to virus infection than younger adults with an increase in differential expression of genes associated with inflammation and a reduction in the expression of type I interferon beta [13]. The age-dependent defects in T-cell and B-cell function and the excess production of type 2 cytokines could lead to a deficiency in control of viral replication and more prolonged proinflammatory responses potentially leading to poor outcome [14].
This study found that coexisting diabetes mellitus(DM) on admission was associated with increased odds of severe cases among hospitalized COVID-19 patients. It is now well recognized that older age and the presence of DM, hypertension, and severe obesity (BMI ≥ 40 kg/m2) increases morbidity and mortality in patients with COVID-19 [5]. Plasma glucose levels and DM are independent predictors for mortality and morbidity in patients with SARS [15]. Certain racial groups such as African Americans, Hispanics, and Native Americans are highly prone to develop DM and disparities in health care make these groups more vulnerable. Potential mechanisms that may increase the susceptibility for COVID-19 in patients with DM include: a) higher affinity cellular binding and efficient virus entry, b) decreased viral clearance, c) diminished T cell function, d) increased susceptibility to hyperinflammation and cytokine storm syndrome, and e) presence of cardiovascular disease [1]. Identification of clinical and biochemical parameters using multiomics approaches that predict severity of the COVID-19 in DM using large data sets is urgently needed.
In this study, we found that cough at admission was associated with in-hospital severe cases in patients with COVID-19. The presentation of cough often indicates that the respiratory system is involved. The mechanism of pulmonary involvement may be that SARS-CoV-2 virus enters alveolar epithelial cells by binding to ACE2 receptors and triggers a systemic inflammatory response, creating an immune dysfunction with a hyperactivity of T lymphocytes and the release of proinflammatory cytokines such as IL-2, IL-6, IL-7, MCP1 and TNF alpha [16]. If the inflammation is protective initially, it appears secondarily that most cellular and tissue lesions are more the result of hyperinflammation than of the direct effect of the virus [16]. These two phenomena may favor at the respiratory level, pulmonary lesions, by hypercapillary permeability and pulmonary edema, leading to acute respiratory distress [17]. Hyperinflammation at the systemic level may lead to vascular, thrombotic and cytokines’ toxicity phenomena, resulting in multisystemic lesions [18, 19].
This study found that increased PCT on admission was associated with increased odds of severe cases among hospitalized COVID-19 patients. PCT is an emerging prognostic marker in COVID-19. Increasing data suggest a link between serum PCT levels and disease severity in patients with COVID-19 [20, 21]. Elevated PCT was also associated with adverse outcomes (OR 13.1; 95% CI [7.37–23.1]). PCT was increased in 22.8% and 30.6% of patients with the severe course and adverse outcome, respectively [22]. PCT is increased in a subset of COVID-19 patients at risk for clinical deterioration and adverse outcome [22]. Our data are consistent with the findings mentioned above. Variance in PCT levels have previously been proposed to differentiate systemic inflammation of bacterial origin from viral origin in community acquired pneumonia and sepsis, with a significant rise indicating bacterial infection [23, 24]. Therefore, most researchers suggest that raised procalcitonin observed in COVID-19 could be due to bacterial co-infection which can cause increased severity and drives systemic sepsis. However, some researchers think that PCT levels in deteriorating patients are increased because of target organ injury. PCT is also associated with altered liver function tests, cardiac injury, and ocular symptoms [25, 26]. Patients with severe COVID-19 infection can develop immune hyperactivation and cytokine release syndrome (CRS) with a massive release of IL-6 [19]. Therefore, whether PCT levels in deteriorating patients are increased because of bacterial infections or target organ injury needs further study.
This study also found that LDH greater than 245 U/L at admission was associated with in-hospital severe cases in COVID-19 patients. LDH is widely distributed in heart, liver, lung and human tissues. Once the tissue is damaged, the serum LDH concentration increased. LDH is one of the predictor of many pulmonary inflammatory diseases, such as obstructive disease, lung infection disease and interstitial lung disease[27, 28]. This study found an association between increased LDH and severe cases in inpatients with COVID-19, which is consistent with the findings of other study[29]. The elevated LDH is due to the direct damage of lung tissue once COVID-19 infected, and on the other hand, hypoxia causes cell damage and increases the permeability of cell membrane, which aggravate the release of LDH. The continuous increase of LDH indicates the exacerbated of the disease. In the course of COVID-19, the elevated of serum LDH can not only be used as a reference index of lung damage, but also reflect the severity of the disease.
Our study is the first to focus on COVID-19 inpatients in Henan province, central China. The findings of this study may be applicable to the general population in China's most populous province. Our study is also one of the few studies on the risk factors associated with severe illness in COVID-19 inpatients, and our data are of great significance for early identification of these risk factors.
Despite the above significant findings, there were still some deficiencies in our study. First, this study was a retrospective study, and some laboratory tests that might be meaningful were not collected, such as IL-6, serum ferritin, T-lymphocyte subset, and the correlation between these indicators and severe illness was not studied as a result. Second, since some patients with incomplete data were excluded from this study, the sample size of this study was small which may limit the promotion of the conclusions of this study in the general hospitalized population. Therefore, prospective multi-center studies with large samples should be carried out in the future to further verify the conclusions of this study.