Is grand-parental smoking associated with adolescent obesity? A three-generational study

Data from previous studies consistently suggest that maternal smoking is positively associated with obesity later in life. Whether this association persists across generations is unknown. We examined whether grand-parental smoking was positively associated with overweight status in adolescence.

Participants were grandmother-mother-child triads in the Nurses' Health Study II (NHS II), the Nurses Mothers' Cohort Study and the Growing up Today Study (GUTS). Grandmothers provided information on their and their partner's smoking during pregnancy with the child's mother. Information on child's weight and height at ages 12 (N=3094) and 17 (N=3433) was obtained from annual or biennial GUTS questionnaires. We used logistic regression to estimate the odds ratios (ORs) of being overweight or obese, relative to normal weight.

Grand-maternal smoking during pregnancy was not associated with overweight status in adolescence. After adjusting for covariates, the OR of being overweight or obese relative to normal weight at age 12 years in girls whose grandmothers smoked 15+ cigarettes daily during pregnancy was 1.21 (95% confidence interval (CI) 0.74-1.98; P(trend)=0.31) and 1.07 (0.65-1.77; P(trend)=0.41) in boys. Grand-paternal smoking during pregnancy was associated with being overweight or obese at age 12 in girls only, but not at age 17 for either sex: the OR for being overweight or obese at age 12 was 1.38 (95% CI 1.01-1.89; P(trend)=0.03) in girls and 1.31 (95% CI 0.97-1.76; P(trend)=0.07) in boys. Among children of non-smoking mothers, the OR for granddaughter obesity for grand-paternal smoking was attenuated and no longer significant (OR 1.28 (95% CI 0.87-1.89; P(trend)=0.18)).

Our findings suggest that the association between maternal smoking and offspring obesity may not persist beyond the first generation. However, grand-paternal smoking may affect the overweight status of the granddaughter, likely through the association between grand-paternal smoking and maternal smoking.