Fig. 2

a Graphs showing the difference in DNA methylation (∆β) at age 10 between each pair of monozygotic (MZ) twins persistently discordant (at ages 10 and 18) for asthma (affected twin − unaffected co-twin) for each of the ten top-ranked differential methylated positions (DMPs). Mean within-twin pair ∆β across all 13 MZ twin pairs is highlighted in red. Error bars represent the ±standard deviation. Consistent within-twin pair differences in DNA methylation are observed across persistently discordant MZ twin pairs at the ten top-ranked DMPs. b Graph showing average within-twin beta difference of (i) persistent-asthma-discordant MZ twins at age 10, (ii) asthma-remission sub-group (twins discordant for asthma at age 10 but the affected twin had remitted at 18, n = 20 twin pairs) and the age-matched concordant unaffected MZ twins (19 twin pairs). Average within-twin differences in DNA methylation are significantly larger at nine of the ten top-ranked DMPs in asthma-discordant twins compared to both the asthma-remission sub-group and twins concordant for no asthma. Between group comparisons of average within-twin beta differences were examined using a one-way ANOVA. ****P < 0.0001, ***P < 0.001, **P < 0.01, *P < 0.05