Background: The current pandemic, COVID-19, caused by a novel coronavirus SARS-CoV-2 has claimed over a million lives worldwide in a year, warranting the need for more research into the wider determinants of COVID-19 outcomes to support evidence-based policies .
Objective: This study aimed to investigate what factors determined the mortality and length of hospitalisation in individuals with COVID-19 . Data Source: This is a systematic review with data from four electronic databases: Scopus, Google Scholar, CINAHL and Web of Science . Eligibility Criteria: Studies were included in this review if they explored determinants of COVID-19 mortality or length of hospitalisation, were written in the English Language, and had available full-text . Study appraisal and data synthesis: The authors assessed the quality of the included studies with the Newcastle Ottawa Scale and the Agency for Healthcare Research and Quality checklist, depending on their study design . Risk of bias in the included studies was assessed with risk of bias assessment tool for non-randomised studies . A narrative synthesis of the evidence was carried out .
Results: The review included 22 studies from nine countries, with participants totalling 239,830 . The included studies quality was moderate to high . The identified determinants were categorised into demographic, biological, socioeconomic and lifestyle risk factors, based on the Dahlgren and Whitehead determinant of health model . Increasing age (ORs 1.04-20.6 , 95% CIs 1.01-22.68) was the common demographic determinant of COVID-19 mortality while living with diabetes (ORs 0.50-3.2 , 95% CIs -0.2-0.74) was one of the most common biological determinants of COVID-19 length of hospitalisation . Review limitation: Meta-analysis was not conducted because of included studies heterogeneity . Conclusion: COVID-19 outcomes are predicted by multiple determinants, with increasing age and living with diabetes being the most common risk factors . Population-level policies that prioritise interventions for the elderly population and the people living with diabetes may help mitigate the outbreak's impact.