Risk factor associations for severe Covid-19, influenza, and pneumonia in people with diabetes to inform future pandemic preparations: UK population-based cohort study

Abstract

Objective This study aimed to compare clinical and sociodemographic risk factors for severe Covid-19, influenza, and pneumonia, in people with diabetes. Design Population-based cohort study. Setting UK primary care records (Clinical Practice Research Datalink) linked to mortality and hospital records. Participants Individuals with type 1 and type 2 diabetes (Covid-19 cohort: N=43,033 type 1 diabetes and N=584,854 type 2 diabetes, influenza and pneumonia cohort: N=42,488 type 1 diabetes and N=585,289 type 2 diabetes). Primary and secondary outcome measures Covid-19 hospitalisation from 1st February 2020-31st October 2020 (pre-Covid-19 vaccination roll-out), and influenza and pneumonia hospitalisation from 1st September 2016-31st May 2019 (pre-Covid-19 pandemic). Secondary outcomes were Covid-19 and pneumonia mortality. Associations between clinical and sociodemographic risk factors and each outcome were assessed using multivariable Cox proportional hazards models. In people with type 2 diabetes, we explored modifying effects of HbA1c and BMI by age, sex, and ethnicity. Results In type 2 diabetes, poor glycaemic control and severe obesity were consistently associated with increased risk of hospitalisation for Covid-19, influenza, and pneumonia. The highest HbA1c and BMI-associated relative risks were observed in people under 70 years. Sociodemographic-associated risk differed markedly by respiratory infection, particularly for ethnicity. Compared to people of white ethnicity, black and south Asian groups had a greater risk of Covid-19 hospitalisation, but a lesser risk of pneumonia hospitalisation. Risk factor associations for type 1 diabetes and for type 2 diabetes mortality, were broadly consistent with the primary analysis. Conclusions Clinical risk factors of high HbA1c and severe obesity are consistently associated with severe outcomes from Covid-19, influenza, and pneumonia, especially in younger people. In contrast, associations with sociodemographic risk factors differed by type of respiratory infection. This emphasises that risk stratification should be specific to individual respiratory infections.