Biomarkers of biological age as predictors of COVID-19 disease severity

Early epidemiological studies suggest the most important predictor of severity of COVID-19 disease course is age. Pre-existing conditions, including diabetes, CVD, hypertension, obesity and other consequences of an unhealthy lifestyle are also associated with increased mortality, indicating that the biological age is more relevant than the chronological age. Because a reliable COVID-19 vaccine is unlikely to available before the maximal infection of COVID-19 has occurred, it is essential to establish reliable tools for patient stratification and identification of individuals at high risk of severe disease. A number of biomarkers aimed at objective estimation of biological age have been developed in the past several years, the most prominent ones being the epigenetic clock(definition) and the glycan clock. A key feature of a good biomarker of biological age is that the difference between chronological and biological age should correlate with known biomarkers of unhealthy lifestyle and that increased biological age should predict future disease development. The original epigenetic clock relied, in part, on chronological age, so several alternative epigenetic clocks, such as the GrimAge methylation clock, were developed. This has been demonstrated for both methylation and glycans. The difference between glycan age and chronological age