Smoking habit from the paternal line and grand-child's overweight or obesity status in early childhood: prospective findings from the lifeways cross-generation cohort study.

BACKGROUND/OBJECTIVES: The role of smoking from the paternal line during the pre-conception period on grand-child's overweight/obesity and associated underlying pathways are uncertain. We examined whether the smoking status from the paternal line was associated with the grand-child's higher weight at birth, and overweight or obesity at 5 and 9 years of age. The grandparental smoking effect from the maternal line was also explored. SUBJECTS/METHODS: Participants were fathers and grandparents and grand-children from the Lifeways Cross Generational Cohort (N = 1021 for the analysis at birth; N = 562 and N = 284 for the analysis at 5 and 9 years, respectively). Paternal and grandparental smoking was defined as smoking versus non-smoking. Children's weight categories compared were high versus normal weight at birth, and overweight/obesity versus normal weight (based on BMI and waist circumference) at age of five and nine years. Logistic regression models were used to estimate the crude and adjusted associations. RESULTS: After adjustment for several child and parental factors, at age five there was an association between paternal smoking and offspring's overweight/obesity based on BMI (Adjusted Odds Ratio (AOR), and 95%CI: 1.76, 1.14-2.71, p-value: 0.010), most marked for boys (AOR: 2.05, 1.06-3.96, p-value: 0.032). These associations remained when confined to the children sample with biological fathers only (overall sample, AOR: 1.92, 1.22-3.02, p-value: 0.005; son, AOR: 2.09, 1.06-4.11, p-value: 0.033). At age 9, the paternal grandmothers' smoking was positively associated with their grandchild's overweight/obesity status based on waist circumference (AOR: 3.29, 1.29-8.37), and especially with that of her granddaughter (AOR: 3.44, 1.11-10.69). These associations remained when analysing only the children sample with biological fathers (overall sample, AOR: 3.22,1.25-8.29, p-value: 0.016; granddaughter, AOR: 3.55, 1.13-11.15, p-value: 0.030). CONCLUSION: The smoking habit from the paternal line is associated with grand-children's adiposity measures during their early childhood, which might be epigenetically transmitted through male-germline cells.