Parents’ smoking onset before conception as related to body mass index and fat mass in adult offspring: Findings from the RHINESSA generation study

Abstract

Emerging evidence suggests that parents’ preconception exposures may influence off- spring health. We aimed to investigate maternal and paternal smoking onset in specific time windows in relation to offspring body mass index (BMI) and fat mass index (FMI). We inves- tigated fathers (n = 2111) and mothers (n = 2569) aged 39–65 years, of the population based RHINE and ECRHS studies, and their offspring aged 18–49 years (n = 6487, mean age 29.6 years) who participated in the RHINESSA study. BMI was calculated from self- reported height and weight, and FMI was estimated from bioelectrical impedance measures in a subsample. Associations with parental smoking were analysed with generalized linear regression adjusting for parental education and clustering by study centre and family. Inter- actions between offspring sex were analysed, as was mediation by parental pack years, parental BMI, offspring smoking and offspring birthweight. Fathers’ smoking onset before conception of the offspring (onset 15 years) was associated with higher BMI in the off- spring when adult (β 0.551, 95%CI: 0.174–0.929, p = 0.004). Mothers’ preconception and postnatal smoking onset was associated with higher offspring BMI (onset <15 years: β1.161, 95%CI 0.378–1.944; onset 15 years: β0.720, 95%CI 0.293–1.147; onset after off- spring birth: β2.257, 95%CI 1.220–3.294). However, mediation analysis indicated that these effects were fully mediated by parents’ postnatal pack years, and partially mediated by parents’ BMI and offspring smoking. Regarding FMI, sons of smoking fathers also had higher fat mass (onset <15 years β1.604, 95%CI 0.269–2.939; onset 15 years β2.590, 95%CI 0.544–4.636; and onset after birth β2.736, 95%CI 0.621–4.851). There was no asso- ciation between maternal smoking and offspring fat mass. We found that parents’ smoking before conception was associated with higher BMI in offspring when they reached adult- hood, but that these effects were mediated through parents’ pack years, suggesting that cumulative smoking exposure during offspring’s childhood may elicit long lasting effects on offspring BMI.