Smoking-Associated DNA Methylation and Offspring Caries Experience: Findings from the GUSTO Study

Self-reported smoking during pregnancy is subject to measurement error, bringing into question previously reported associations with offspring caries experience. We evaluated whether a previously identified prenatal smoking-associated DNA methylation (DNAm) signature, and separately gestational smoking indexed through self-report and plasma cotinine, was associated with offspring caries. The Growing Up in Singapore Towards healthy Outcomes (GUSTO) cohort (n = 577 mother-child dyads, recruited from June 2009-September 2010) ascertained gestational smoking exposure (by questionnaires and plasma cotinine), DNAm (using umbilical cord tissue), and child dental caries (by clinical examinations at age 3 y). We used zero-inflated Poisson regression to evaluate whether a weighted smoking-associated DNAm risk score (wMRS_DNAm) was associated with the count of tooth surface caries, adjusted for maternal age, education, ethnicity, breastfeeding, preterm status, child sex, and toothbrushing frequency. Of the women, 53% were never smokers and 3% were heavy smokers; children had a mean (standard deviation) of 2.47 (5.20) decayed, missing, and filled surfaces. The mean wMRS_DNAm for the 16 CpGs included was -0.21 (0.02), with an interquartile range of 0.02. Each additional IQR of wMRS_DNAm was associated with a 20% higher adjusted caries experience risk, relative risk (RR) (95% confidence interval [CI]) = 1.20 (1.10, 1.31), and a lower adjusted odds of excess zeros, odds ratio (95% CI) = 0.91 (0.70, 1.17). Children of mothers who smoked during gestation (based on self-report/cotinine) also had higher adjusted caries experience risk: relative risk (RR) (95% CI) = 1.31 (1.11, 1.55) and RR (95% CI) = 1.12 (0.81, 1.54) for light and heavy smoking, respectively. These findings corroborate a link between prenatal smoking and offspring caries and provide novel information of a positive association between maternal smoking-associated DNAm risk scores and greater offspring caries experience. While replication in independent studies is warranted as these results are based on CpGs derived from umbilical cord DNA, these findings point to a need for greater smoking cessation support.