In-Hospital Mortality Risk of Older Patients With COVID-19 Infection.

To the Editor:

I read the recent article published in this journal and written by Covino et al with great interest. The authors conducted a prospective study to evaluate the risk factors of mortality in adult COVID-19 patients aged ≥80 years. The adjusted hazard ratios (HRs) (95% CIs) of severe disease, ≥3 comorbidities, male sex, and vulnerability for the in-hospital death were 1.87 (1.31-2.59), 1.54 (1.11-2.13), 1.46 (1.14-1.87), and 6.93 (1.69-28.27), respectively. Regarding the severity of frailty, the adjusted HR (95% CI) of highest frailty for the in-hospital death was 12.55 (2.96-53.21). I have comments on the statistical validity, sex difference, and body mass index (BMI).

First, the number of deceased patients without frailty was 2, and they set patients without frailty as a control group. Although the numbers of deceased patients with moderate and severe frailty were 128 and 157, unstable estimates of mortality risk by frailty may be observed in wide ranges of HR. The authors should increase the number of controls to keep stable estimates by multivariate analysis with Cox regression model.

Second, the authors handled patients with a median age of 85 years. As life expectancy at birth in males is shorter than that in females, the mortality risk in males would predominantly increase in this population. HR of males against females for death may be increased in subjects without COVID-19 infection, and stratified analysis by sex should be added to specify the risk factors of mortality in patients with COVID-19 infection. In addition, interaction among independent variables in multivariate analysis cannot be fully adjusted, if the authors do not consider an interaction model among independent variables.

Finally, Kananen et al evaluated the association between BMI and mortality in older COVID-19 patients with a median age of 83 years. The adjusted odds ratio (95% CI) of patients with BMI <18.5 for in-hospital mortality was 2.30 (1.17-4.31), and malnutrition was also a risk of in-hospital mortality. In contrast, increased BMI was not significantly associated with in-hospital mortality. Poor nutritional status is closely related to the increased risk of mortality in older subjects in general, and risk assessment of mortality should be comprehensively evaluated in patients with COVID-19 infection by including variables on nutritional status.