CLOCK and COVID-19: In addition, all clocks were strongly correlated with one another in all groups (r > 0.8, p < 0.0001; Fig. 1 and Supplementary Fig. 1), except that PhenoAge clock showed weaker correlations with other clocks in the severe COVID-19 group (r = 0.73 ~ 0.77, p < 0.0001).