Human transgenerational observations of regular smoking before puberty on fat mass in grandchildren and great-grandchildren

Previously, using data from the Avon Longitudinal Study of Parents and Children (ALSPAC) we showed that sons of fathers who had started smoking regularly before puberty (<13 years) had increased fat mass during childhood, adolescence, and early adulthood. We now show that if the paternal grandfather had started smoking pre-puberty, compared with later in childhood (13-16 years), his granddaughters, but not grandsons, had evidence of excess fat mass at two ages: mean difference +3.54Kg; (P with 1-tailed test)=0.043 at 17 years, and +5.49Kg; (P1=0.016) at age 24. When fathers of maternal grandfathers had started smoking pre-puberty, their great-granddaughters, but not great-grandsons, had excess body fat: +5.35Kg (P1=0.050) at 17, and +6.10Kg (P1=0.053) at 24 years. Similar associations were not found with lean mass, in a sensitivity analysis.
To determine whether these results were due to the later generations starting to smoke pre-puberty, further analyses omitted those in subsequent generations who had smoked regularly from <13 years. The results were similar.
If these associations are confirmed in another dataset or using biomarkers, this will be one of the first human demonstrations of transgenerational effects of an environmental exposure across four generations.