Impact of Age and Comorbid Conditions on Incidence Rates of COVID-19-Associated Hospitalizations, 2020-2021

COVID-19-associated hospitalization rates by age and comorbid conditions can more precisely assess risk for severe illness and target prevention and treatment strategies.

We performed a retrospective study to estimate population-based COVID-19-associated hospitalization among patients by age and selected comorbid conditions in three hospital systems in Rochester and New York City (NYC), NY. Incidence rate ratios (IRR) comparing incidence rates for patients with and without these comorbidities were determined.

From March 2020 to December 2021, 7779 patients were hospitalized with COVID-19 of whom 43.8% had ≥3 comorbid conditions. Overall annual incidence ranged from 325.3 to 965.8 per 100,000 persons. Age group-specific incidence was lowest in children 10-14 years (range 4.4-58.9) and highest in adults ≥85 years (range 2790.5-5889.6). Incidence rates for comorbid conditions generally increased with increasing age while IRR decreased with increasing age. Children in NYC 5-17 years with asthma or obesity had 3.4 and 53.3 times higher hospitalization rates, respectively, than children without these conditions. Adults in all age groups with obesity, diabetes, coronary artery disease, or congestive heart failure CHF had 1.6-4.7 times, 1.7-7.2 times, 2.0-10.1 times, or 1.7-20.2 times higher hospitalization rates, respectively, than those without these conditions. Adults ≥50 years with asthma had 1.5 to 1.8 times higher hospitalization rates than those without asthma.

The burden of hospitalization with COVID-19 was high, particularly among adults ≥85 years and adults with obesity, diabetes, CAD, or CHF. However, the impact of comorbidities was less in older adults. Population-based incidence rates by age and comorbidities provide more precise estimates of the benefits of vaccines and antiviral medications.