Is Age the Most Important Risk Factor in COVID-19 Patients? The Relevance of Comorbidity Burden: A Retrospective Analysis of 10,551 Hospitalizations

Abstract

Damià Valero-Bover,1,2 David Monterde,2,3 Gerard Carot-Sans,1,2 Miguel Cainzos-Achirica,4,5 Josep Comin-Colet,6– 8 Emili Vela,1,2 Montse Clèries,1,2 Júlia Folguera,1,2 Sònia Abilleira,9 Miquel Arrufat,3 Yolanda Lejardi,3 Òscar Solans,2,10 Toni Dedeu,11 Marc Coca,1,2 Pol Pérez-Sust,1 Caridad Pontes,1,2,12 Jordi Piera-Jiménez1,2,13 1Catalan Health Service, Barcelona, Spain; 2Digitalization for the Sustainability of the Healthcare System (DS3) – Institut d’Investigacions Biomèdiques de Bellvitge (IDIBELL), Barcelona, Spain; 3Catalan Institute of Health, Barcelona, Spain; 4Center for Outcomes Research, Houston Methodist, Houston, TX, USA; 5Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease, Johns Hopkins Medical Institutions, Baltimore, MD, USA; 6Cardiology Department, Bellvitge University Hospital (IDIBELL), Barcelona, Spain; 7Department of Medicine, University of Barcelona, Hospitalet de Llobregat, Barcelona, Spain; 8CIBER Cardiovascular (CIBERCV), L’Hospitalet de Llobregat, Barcelona, Spain; 9CIBER Epidemiología y Salud Pública (CIBERESP), Barcelona, Spain; 10Health Department, eHealth Unit, Barcelona, Spain; 11WHO European Centre for Primary Health Care, Almaty, Kazakhstan; 12Department of Pharmacology, Autonomous University of Barcelona, Barcelona, Spain; 13Faculty of Informatics, Telecommunications and Multimedia, Universitat Oberta de Catalunya, Barcelona, SpainCorrespondence: Jordi Piera-Jiménez, Catalan Health Service, Gran Via de les Corts Catalanes 587, Barcelona, 08007, Spain, Tel [phone], Email [email protected]: To assess the contribution of age and comorbidity to the risk of critical illness in hospitalized COVID-19 patients using increasingly exhaustive tools for measuring comorbidity burden.Patients and Methods: We assessed the effect of age and comorbidity burden in a retrospective, multicenter cohort of patients hospitalized due to COVID-19 in Catalonia (North-East Spain) between March 1, 2020, and January 31, 2022. Vaccinated individuals and those admitted within the first of the six COVID-19 epidemic waves were excluded from the primary analysis but were included in secondary analyses. The primary outcome was critical illness, defined as the need for invasive mechanical ventilation, transfer to the intensive care unit (ICU), or in-hospital death. Explanatory variables included age, sex, and four summary measures of comorbidity burden on admission extracted from three indices: the Charlson index (17 diagnostic group codes), the Elixhauser index and count (31 diagnostic group codes), and the Queralt DxS index (3145 diagnostic group codes). All models were adjusted by wave and center. The proportion of the effect of age attributable to comorbidity burden was assessed using a causal mediation analysis.Results: The primary analysis included 10,551 hospitalizations due to COVID-19; of them, 3632 (34.4%) experienced critical illness. The frequency of critical illness increased with age and comorbidity burden on admission, irrespective of the measure used. In multivariate analyses, the effect size of age decreased with the number of diagnoses considered to estimate comorbidity burden. When adjusting for the Queralt DxS index, age showed a minimal contribution to critical illness; according to the causal mediation analysis, comorbidity burden on admission explained the 98.2% (95% CI 84.1– 117.1%) of the observed effect of age on critical illness.Conclusion: Comorbidity burden (when measured exhaustively) explains better than chronological age the increased risk of critical illness observed in patients hospitalized with COVID-19.Keywords: COVID-19, comorbidities, comorbidity burden, risk assessment, hospitalized patients, case-mix tool

Keywords

• covid-19
• comorbidities
• comorbidity burden
• risk assessment
• hospitalized patients
• case-mix tool