PDE4C and COVID-19: More recently, in a set of post-COVID19 infection and COVID19-free individuals, biological age as determined by a set of four CpGs contained within the genes ASPA, EDARADD, ELOVL2 and PDE4C found that the post-COVID19 infection participants had a biological age 9 years older than uninfected counterparts, with the effect being more significant in younger individuals (Bekaert et al., 2015; Mongelli et al., 2021).