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Obesity, old age and frailty are the true risk factors for COVID-19 mortality and not chronic disease or ethnicity in Croydon.

Background: Coronavirus-19 (COVID-19) mortality in hospitalised patients is strongly associated with old age, nursing home residence, male sex and obesity, with a more controversial association with ethnicity and chronic diseases, in particular diabetes mellitus. Further complicating the evaluation of the independent impacts of these risk factors is the failure to control for frailty in the published studies thus far. Aim: To determine the true risk factors for mortality in patients confirmed to have COVID-19 in Croydon needing hospital admission and to evaluate the independence of these risk factors in this group after adjusting for body mass index (BMI) and frailty. Methods: This observational study retrospectively reviewed hospital electronic medical records of 466 consecutive patients who were admitted to Croydon University Hospital confirmed positive by rapid PCR test from 11th March 2020 to 9th April 2020. Statistical analysis was performed by multiple unconditional and univariate logistic regression. Results: After multivariate analysis, male sex [OR 1.44 (CI 0.92-2.40)], age (per year) [OR 1.07 (CI 1.05-1.09)], morbid obesity (BMI > 40 kg/m2 vs reference BMI 18.5-24.9 kg/m2 ) [OR 14.8 (CI 5.25-41.8)], and nursing home residence (OR 3.01 (CI 1.56-5.79) were independently associated with COVID-19 mortality with no statistically significant association found with chronic diseases or ethnicity. In the non-nursing home population, after adjusting for age and sex, the odds ratio for type 2 diabetes mellitus (T2DM) as a risk factor was 1.64 (CI 1.03-2.61, p = 0.03) and was and was attenuated to 1.30 (CI 0.78-2.18)) after controlling for BMI; the association of mortality with male sex was strengthened [OR 1.66 (CI 0.96-2.87)] and that for ethnic minority patients was weakened [South Asians [from OR 1.30 (CI 0.67-2.53)) to OR 1.21 (CI 0.60-2.46)]; African Caribbeans [from OR 1.24 (CI 0.65-2.34) to OR 1.16 (CI 0.58-2.30)]. There was a borderline but potentially large protective effect (p= 0.09) in patients who were on anticoagulation drugs prior to admission [OR 0.56 (CI 0.28-1.11)]. Conclusion: Our study found no significant effect of ethnicity and chronic diseases as independent risk factors on COVID-19 mortality in Croydon population whereas male sex, high BMI, old age and frailty were found to be independent risk factors. Routine prophylactic treatment with anticoagulant drugs in the high-risk COVID-19 population warrants further prompt investigation.