Risk factors for severe outcomes of COVID-19: a rapid review
Authors: Wingert Aireen , Pillay Jennifer , Gates Michelle , Guitard Samantha , Rahman Sholeh , Beck Andrew , Vandermeer Ben , Hartling Lisa 
Published: September 2020

ABSTRACTBackgroundIdentification of high-risk groups is needed to inform COVID-19 vaccine prioritization strategies in Canada. A rapid review was conducted to determine the magnitude of association between potential risk factors and risk of severe outcomes of COVID-19.MethodsMethods, inclusion criteria, and outcomes were prespecified in a protocol that is publicly available. Ovid MEDLINE(R) ALL, Epistemonikos COVID-19 in L·OVE Platform, and McMaster COVID-19 Evidence Alerts, and select websites were searched to 15 June 2020. Studies needed to be conducted in Organisation for Economic Co-operation and Development countries and have used multivariate analyses to adjust for potential confounders. After piloting, screening, data extraction, and quality appraisal were all performed by a single reviewer. Authors collaborated to synthesize the findings narratively and appraise the certainty of the evidence for each risk factor-outcome association.ResultsOf 3,740 unique records identified, 34 were included in the review. The studies included median 596 (range 44 to 418,794) participants with a mean age between 42 and 84 years. Half of the studies (17/34) were conducted in the United States and 19/34 (56%) were rated as good quality. There was low or moderate certainty evidence for a large (≥2-fold) association with increased risk of hospitalization in people having confirmed COVID-19, for the following risk factors: obesity class III, heart failure, diabetes, chronic kidney disease, dementia, age over 45 years (vs. younger), male gender, Black race/ethnicity (vs. non-Hispanic white), homelessness, and low income (vs. above average). Age over 60 and 70 years may be associated with large increases in the rate of mechanical ventilation and severe disease, respectively. For mortality, a large association with increased risk may exist for liver disease, Bangladeshi ethnicity (vs. British white), age over 45 years (vs. <45 years), age over 80 years (vs. 65-69 years), and male gender in those 20-64 years (but not older). Associations with hospitalization and mortality may be very large (≥5-fold increased risk) for those aged over 60 years.ConclusionAmong other factors, increasing age (especially >60 years) appears to be the most important risk factor for severe outcomes among those with COVID-19. There is a need for high quality primary research (accounting for multiple confounders) to better understand the level of risk that might be associated with immigration or refugee status, religion or belief system, social capital, substance use disorders, pregnancy, Indigenous identity, living with a disability, and differing levels of risk among children.PROSPERO registrationCRD42020198001What is already knownThe novel nature of COVID-19 means that in many countries there are currently no pre-determined priority groups for the receipt of the eventual COVID-19 vaccine(s).Primary research is rapidly emerging, but consensus on who might be at increased risk of severe outcomes from COVID-19 has not been established.What this study addsThis rapid review shows that advancing age (>45 years and especially >60 years) may be the most important risk factor for hospitalization and mortality from COVID-19.Other important risk factors for severe disease identified by this review include several pre-existing chronic conditions (class III obesity, heart failure, diabetes, chronic kidney disease, liver disease, dementia), male gender, Black race/ethnicity (vs. non-Hispanic white), Bangladeshi ethnicity (vs. British white), low income (vs. high), and homelessness.