Diabetes and COVID-19: Population Impact 18 Months Into the Pandemic

Eighteen months into the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (coronavirus disease 2019 [COVID-19]) pandemic, epidemiologic studies indicate that diabetes is a central contributor to severe COVID-19 morbidity, and, conversely, COVID-19 has had a devastating effect on the population with diabetes. In this literature synthesis, we summarize the relationship of diabetes to COVID-19-related morbidity and mortality, discuss the predictors of severe adverse outcomes and implications of the overall pandemic, and critique the current status of and identify needs for epidemiologic studies for the next phase of the pandemic. Case series show that ∼30-40% of people with COVID-19-related hospitalization, severe morbidity requiring intensive care, and/or death have type 2 or type 1 diabetes. Among hospitalized individuals with diabetes, ∼21-43% required intensive care and case fatality is ∼25%. Risk of severe morbidity and mortality is 100-250% higher among people with diabetes than those without, even after adjustment for sociodemographic factors and comorbid conditions. Impact on the general population with diabetes has been similarly dire, as overall mortality rates were 50% higher than historical trends, a net increase more than twice that of the general population. Of the excess deaths, ∼75-80% are not officially attributed to COVID-19, which raises unanswered questions about missed attribution or collateral impact. Many predictors of poor outcomes have been identified, particularly comorbid conditions (chronic kidney disease, coronary heart disease, and heart failure), concurrent obesity, and acute and chronic poor HbA_1c control, that point to the potential to reduce severe morbidity and mortality in its next stages. However, response to the continuing pandemic will benefit from population-wide studies with broader examination of the risks of exposure, infection, and hospitalization, for which few data currently exist. The indirect impact of the pandemic's effects on health services, health behaviors, disease management, care, control, and complications has not been well quantified; determining this impact will be essential to lessen the future impact. Expanding epidemiologic studies of the relationship of diabetes to COVID-19 beyond few high-income countries will also be essential to limit the burden in low- and middle-income countries where 80% of individuals with diabetes reside and where the COVID-19 pandemic has been so damaging.