The anthropometry of children and adolescents may be influenced by the prenatal smoking habits of their grandmothers: A longitudinal cohort study

Our program of research into transgenerational effects of cigarette smoking (Miller et al., 2014; Northstone et al., 2014) was instigated as a result of studies from Sweden. These were based on samples of individuals born close to the Arctic Circle in the town of Overkalix. Their longevity and other health outcomes were linked to detailed historical records of harvests experienced by their ancestors (Bygren et al., 2001). Using three independent birth cohorts in the years 1890, 1905, and 1920, Kaati et al. (2002) showed that the paternal grandfathers' plentiful food supply in mid-childhood was associated with a fourfold increased chance of diabetes on the grandchild's death certificate [95% CI 1.3, 12.9]. Their study also showed that cardiovascular mortality in the study individuals was reduced when there had been poor food supply in the father's mid-childhood. Subsequently, sex-specific analysis of the data showed that the mortality rate of the men born in the target years was linked to their paternal grandfather's food supply in mid-childhood, whereas the mortality rate of the women studied was associated solely with their paternal grandmother's food supply (Pembrey et al., 2006). This association was shown in two of three independent cohorts. Exposure sensitive periods involved both paternal grandparents' mid-childhood but also the fetal/infant period for the paternal grandmothers. In the UK, since the Second World War, there have been no particular years of starvation or glut. In the search for an environmental feature that we could time in regard to the age of exposure at which it occurred, we have chosen the smoking habits of the individual parents. It is well recognized that smoking has strong effects on various physiological systems, and results in a loss of appetite and general reduction in weight compared with nonsmokers (Chiolero et al., 2008). Previously, using the Avon Longitudinal Study of Parents and Children (ALSPAC), we have shown that fathers who started smoking regularly between the ages of 8 and 11 had boys (but not girls) with increased body mass index (BMI), waist circumference, and body fat mass as teenagers (Northstone et al., 2014). We have also shown that nonsmoking mothers exposed prenatally to their own mothers' smoking delivered children who were larger at birth (Miller et al., 2014). After adjustment, the average birth weight, birth length, and BMI measurements of the boys (but not the girls) were greater if the maternal grandmother smoked prenatally: birth weight = +61 [95% CI +30, +92] g; birth length = +0·19 [95% CI +0·02, +0·35] cm; birth BMI = +1·6 [95% CI +0·6, +2·6] g/m2. In a parallel paper (Pembrey et al., 2014), we have shown that exposure of the father to his mother's smoking resulted in a reduction in birth head circumference of his sons if the study mother also smoked in pregnancy, and that this was reflected in reduced IQ in this group. Here, we examine the growth of these children from ages 7 to 17 to determine whether prenatal smoke exposure of either parent is associated with the growth of the offspring, including body composition, and whether it is sex-specific and/or depends on whether the study mother smoked in pregnancy.