Hospital load and increased COVID-19 related mortality - a nationwide study in Israel

Rossman, H.; Meir, T.; Somer, J.; Shilo, S.; Gutman, R.; Ben Arie, A.; Segal, E.; Shalit, U.; Gorfine, M.

The rapid spread of Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) worldwide and the disease caused by the virus, coronavirus disease 19 (COVID-19), has caused a global pandemic with devastating social and economic consequences. Throughout the pandemic, several health systems were overwhelmed in light of the rapid emergence of new cases within a short period of time. The heavy workload imposed on hospital services might have negatively affected patients' outcomes and exacerbated mortality rates. Here, we assessed excess in-hospital mortality across the Israeli healthcare system, using a model developed for predicting patient mortality based on data of day-by-day patient disease course. Mortality predictions were made using Monte-Carlo methods based on a multistate survival analysis and a set of Cox regression models, first constructed and validated on a nationwide cohort during the first stages of the pandemic in Israel. We show that during a peak of hospitalizations in September and October 2020, patient deaths significantly exceeded the model's mortality predictions, while reverting to match the predictions as patient load subsided in October, and showing signs of renewed excess mortality as hospital load is increasing again since late December 2020. Our work emphasizes that even in countries in which the healthcare system did not reach a specific point defined as insufficiency, the increase in hospital workload was associated with higher patient mortality, while ruling out factors related to changes in the hospitalized population. In addition, our study highlights the importance of quantifying excess mortality in order to assess quality of care, and define an appropriate carrying capacity of severe patients in order to guide timely healthcare policies and allocate appropriate resources. Full model code is available for use at https://github.com/JonathanSomer/covid-19-multi-state-model.