Big data evidence of the impact of COVID-19 hospitalizations on mortality rates of non-COVID-19 critically ill patients

Abstract

The COVID-19 virus caused a global pandemic leading to a swift policy response. While this response was designed to prevent the spread of the virus and support those with COVID-19, there is growing evidence regarding measurable impacts on non-COVID-19 patients. The paper uses a large dataset from administrative records of the Brazilian public health system (SUS) to estimate pandemic spillover effects in critically ill health care delivery, i.e. the additional mortality risk that COVID-19 ICU hospitalizations generate on non-COVID-19 patients receiving intensive care. The data contain the universe of ICU hospitalizations in SUS from February 26, 2020 to December 31, 2021. Spillover estimates are obtained from high-dimensional fixed effects regression models that control for a number of unobservable confounders. Our findings indicate that, on average, the pandemic increased the mortality risk of non-COVID-19 ICU patients by 1.296 percentage points, 95% CI 1.145-1.448. The spillover mortality risk is larger for non-COVID patients receiving intensive care due to diseases of the respiratory system, diseases of the skin and subcutaneous tissue, and infectious and parasitic diseases. As of July 2023, the WHO reports more than 6.9 million global deaths due to COVID-19 infection. However, our estimates of spillover effects suggest that the pandemic's total death toll is much higher.

Figure 1

(A) Evolution over 96 epidemiological weeks (from February 26, 2020 to December 31, 2021) of the number of ICU patients, by COVID diagnosis, and (7 day) moving average of the mortality rate of non-COVID-19 patients. (B) Estimates of the spillover mortality risk, i.e. $\widehat{f\left(P_{\mathit{jt}}\right)}$ as estimated by model (1), and its 95% confidence interval, aggregated (averaged) by epidemiological week. The horizontal line represents the overall average of 1.3%. (C) The spillover mortality risk, $\widehat{f\left(P_{\mathit{jt}}\right)}$, as a function of the proportion of ICU patients diagnosed with COVID-19, $P_{\mathit{jt}}$. (D) Average spillover mortality risks and 95% confidence intervals, by chapters of the ICD-10 disease classification.

Figure 2

Evolution of the average proportion of COVID-19 ICU patients over 96 epidemiological weeks (from February 26, 2020 to December 31, 2021). The vertical line at week 37 represents the demarcation between Brazil’s first and second COVID-19 waves. The ${\mathit{RRR}}_1$ represents the relative spillover mortality risk ratio during the first wave, i.e. ${\mathit{RRR}}_1=\frac{Risk\left(P,e,a,k,,W,a,v,e,1\right)}{Risk(Off\text{-}peakWave1)}=\frac{2.86\%}{1.15\%}=2.5(95\%\mathrm{CI}1.95-3.05)$. For the second wave, ${\mathit{RRR}}_2=\frac{Risk\left(P,e,a,k,,W,a,v,e,2\right)}{Risk(Off\text{-}peakWave2)}=\frac{1.58\%}{0.51\%}=3.1(95\%\mathrm{CI}1.29-4.95)$.