Prepubertal start of father's smoking and increased body fat in his sons: further characterisation of paternal transgenerational responses.
Despite interest in the idea that transgenerational effects of adverse exposures might contribute to population health trends, there are few human data. This non-genetic inheritance is all the more remarkable when transmission is down the male-line as reported in a historical Swedish study, where the paternal grandfather's food supply in mid childhood was associated with the mortality rate in his grandsons. Using the Avon Longitudinal Study of Parents and Children's questionnaire data on smoking and smoking onset from 9886 fathers, we examined the growth of their children from 7-17 years. Adjusting for potential confounders, we assessed associations between body mass index (BMI), waist circumference, total fat mass and lean mass with the age at which the father had started smoking regularly. Of 5376 fathers who reported having ever smoked, 166 reported regular smoking <11 years of age. Before adjustment, those offspring whose fathers started smoking <11 years had the highest mean BMIs at each age tested. The adjusted mean differences in BMI, waist circumference and total fat mass in those sons whose fathers started smoking <11 years, compared with all other sons, increased with age, being significantly greater from 13 years onwards. There were no significant BMI associations in daughters, but they showed a reduction in total lean mass. Our results highlight the importance of the developmental timing of the paternal exposure as well as gender differences in offspring outcomes. Smoking by boys in mid childhood may contribute to obesity in adolescent boys of the next generation.