Comparison of Clinical Characteristics and Outcomes of COVID-19 Between Young and Older Patients: A Multicenter, Retrospective Cohort Study.

Background Outcomes of coronavirus disease 2019 (COVID-19) have been reported to be different in the young and elderly populations. However, previous studies examining these characteristics and differences in outcomes between the two groups had a small sample size. Therefore, in this study, we evaluate the differences between young and elderly patients using a large multicenter dataset. Methodology We conducted a retrospective study of 1,116 consecutive COVID-19 patients admitted to two hospitals in southern California in the United States between March 2020 and March 2021. In this study, we categorized patients into two age groups: less than 65 years and 65 years and above. Finally, Kaplan-Meier and backward selection Cox multivariate regression analyses were done using mortality as the dependent variable. Results Our analysis showed increased survival in patients aged less than 65 years compared to those aged 65 years or above (p < 0.001). Furthermore, in patients aged 65 years and above, age (hazard ratio (HR) = 1.05; p < 0.001), C-reactive protein (CRP) (HR = 1.05; p < 0.001), and bradycardia (HR = 2.1; p < 0.001) were significantly associated with mortality. Similarly, CRP (HR 1.05; p = 0.02) was significantly associated with mortality in patients aged less than 65 years. However, contrary to many studies, being male (HR = 0.46; p = 0.002) was protective against mortality in patients aged less than 65 years. Conclusions Our study showed that the predictors of mortality in COVID-19 patients differed by age group. While age, CRP, and bradycardia were associated with mortality in those aged less than 65 years, only CRP was associated with mortality in those aged 65 years and above.