COVID-19 Pandemic Inpatient Mortality Showed a Stepwise Increase by Age

For patients hospitalized during the COVID-19 pandemic, overall mortality showed a stepwise increase by age, and for those requiring intubation, mortality peaked among patients 70 to 79 years of age, according to a research letter published in Chest.

Research letter authors sought to characterize in-hospital mortality rates during the 3 COVID-19 pandemic surges by age, intubation, and vaccination status in US adults. To accomplish this, the authors conducted a review of data from the hospitalized sample of the COVID EHR Cohort at the University of Wisconsin Study, a retrospective cohort with electronic hospital records on almost 150,000 COVID-19 patients admitted from February 2020 through January 2022 to 21 health systems.

The current analysis included 62,848 patients at least 20 years old with COVID-19 who: (1) were hospitalized for at least 24 hours or, within 24 hours of hospital admission, had died or were admitted to the ICU; and (2) had an ICD-10 diagnosis of COVID-19, pneumonia due to coronavirus, or post-COVID-19 condition unspecified. All patients were admitted during 1 of 3 COVID-19 surges corresponding to Alpha, Delta, and Omicron dominant strains of SARS-CoV-2. Investigators used multivariate logistic generalized linear mixed models to predict mortality from intubation, full vaccination, and surge period.

The researchers found an increase in overall mortality rates with age and intubation. Unvaccinated patients aged 90 or more (16%) during the Alpha wave represented peak overall mortality. The highest mortality among non-intubated patients over all 3 waves occurred in this same group (13.7%). During the Delta wave, peak mortality of any group occurred among vaccinated intubated patients 70 to 79 years of age (60.3%).

Investigators noted intubation was strongly related to mortality in the fully adjusted model (odds ratio [OR], 31.28; 95% CI, 28.22-34.67; P <.001). Relative to Alpha, mortality was higher during Delta (OR, 1.31; 95% CI, 1.15-1.50; P <.001), but not Omicron (OR, 0.96; 95% CI, 0.84-1.11; P =.591). Relative to Alpha, there was a stronger relationship between intubation and mortality in Delta but not omicron.

With respect to vaccination, the researchers found that in those sick enough to require mechanical ventilation, mortality rates did not vary according to vaccination status. However, the researchers also found full vaccination was protective against overall mortality (OR, 0.66; 95% CI, 0.57-0.76; P <.001).

The analysis found age to be a strong predictor of mortality. Compared with patients 20 to 29 years of age, adjusted odds of death increased progressively with age — from an odds ratio of 1.58 for patients aged 30 to 39 years to an odds ratio of 30.78 for patients aged 90 and above.

Analysis limitations include the exclusion of outpatients, lack of analysis of the effect of COVID-19-related medications, and unaccounted-for confounders relating to differing phases of the pandemic.

The investigators noted that “though intubated patients had differentially higher mortality during the delta wave, mortality among those requiring intubation peaked among those aged 70-79 years during all three surges.” The researchers concluded that “these data suggest that the magnitude of the relationship between intubation and mortality is dynamic and continued research and clinical guidance is needed as SARS-CoV-2 evolves.”