Figure 1. The epigenetic clock and Asthma Across the Life Course . Panel A illustrates different environmental exposures which may alter the rate of the epigenetic clock. Panel B is an illustrative representation of the proportion of male vs. female asthmatics over the life stages. Arrows show key changes in sex-specific patterns of asthma prevalence as extrapolated from25,91,92and are intended for illustrative purposes only. Panel C shows the different life stages. DNAm during periods of significant hormone changes (e.g., puberty, pregnancy, and menopause) DNA is particularly vulnerable to alteration by environmental exposures. Panel D shows the key genes undergoing changes in methylation during development (39,40,88).