Importance: Mortality is an important measure of the severity of a pandemic. This study aimed to understand how mortality by age of hospitalized patients who were tested for SARS-CoV-2 has changed over time.
Objective: To evaluate trends in in-hospital mortality among patients who tested positive for SARS-CoV-2.
Design, setting, and participants: This retrospective cohort study included patients who were hospitalized for at least 1 day at 1 of 209 US acute care hospitals of variable size, in urban and rural areas, between March 1 and November 21, 2020. Eligible patients had a SARS-CoV-2 polymerase chain reaction (PCR) or antigen test within 7 days of admission or during hospitalization, and a record of discharge or in-hospital death.
Exposure: SARS-CoV-2 positivity.
Main outcomes and measures: SARS-CoV-2 infection was defined as a positive SARS-CoV-2 PCR or antigen test within 7 days before admission or during hospitalization. Mortality was extracted from electronically available data.
Results: Among 503 409 admitted patients, 42 604 (8.5%) had SARS-CoV-2-positive tests. Of those with SARS-CoV-2-positive tests, 21 592 (50.7%) were male patients. Hospital admissions among patients with SARS-CoV-2-positive tests were highest in the group aged 65 years or older (19 929 [46.8%]), followed by those aged 50 to 64 years (11 602 [27.2%]) and 18 to 49 years (10 619 [24.9%]). Hospital admissions among patients 18 to 49 years of age increased from 1099 of 5319 (20.7%) in April to 1266 of 4184 (30.3%) in June and 2156 of 7280 (29.6%) in July, briefly exceeding those in the group 50 to 64 years of age (June: 1194 of 4184 [28.5%]; 2039 of 7280 [28.0%]). Patients with SARS-CoV-2-positive tests had higher in-hospital mortality than patients with SARS-CoV-2-negative tests (4705 [11.0%] vs 11 707 of 460 805 [2.5%]; P < .001). In-hospital mortality rates increased with increasing age for both patients with SARS-CoV-2-negative tests and SARS-CoV-2-positive tests. In patients with SARS-CoV-2-negative tests, mortality increased from 45 of 11 255 (0.4%) in those younger than 18 years to 4812 of 107 394 (4.5%) in those older than 75 years. In patients with SARS-CoV-2-positive tests, mortality increased from 1 of 454 (0.2%) of those younger than 18 years to 2149 of 10 287 (20.9%) in those older than 75 years. In-hospital mortality rates among patients with SARS-CoV-2-negative tests were similar for male and female patients (6273 of 209 086 [3.0%] vs 5538 of 251 719 [2.2%]) but higher mortality was observed among male patients with SARS-CoV-2-positive tests (2700 of 21 592 [12.5%]) compared with female patients with SARS-CoV-2-positive tests (2016 of 21 012 [9.60%]). Overall, in-hospital mortality increased from March to April (63 of 597 [10.6%] to 1047 of 5319 [19.7%]), then decreased significantly to November (499 of 5350 [9.3%]; P = .04), with significant decreases in the oldest age groups (50-64 years: 197 of 1542 [12.8%] to 73 of 1341 [5.4%]; P = .02; 65-75 years: 269 of 1182 [22.8%] to 137 of 1332 [10.3%]; P = .006; >75 years: 535 of 1479 [36.2%] to 262 of 1505 [17.4%]; P = .03).
Conclusions and relevance: This nationally representative study supported the findings of smaller, regional studies and found that in-hospital mortality declined across all age groups during the period evaluated. Reductions were unlikely because of a higher proportion of younger patients with lower in-hospital mortality in the later period.