BODY MASS INDEX IS ASSOCIATED WITH MATERNAL LINES BUT HEIGHT IS HERITABLE ACROSS FAMILY LINES IN THE LIFEWAYS CROSS-GENERATION COHORT STUDY IN REPUBLIC OF IRELAND

INTRODUCTION: Increasing levels of body mass index (BMI) in populations and high levels of obesity are problems associated with modern societies but heritability patterns across generations and over the life-course are not fully understood.  In the Lifeways familial cohort study, spanning three generations, patterns across families associated with body mass index (BMI) were examined.

METHODS: This longitudinal study collected height and weight data at three ages of the index child, birth, age 5 and age 9. There were 924 children with measurements at birth, with 506 mothers, 452 fathers, and grandparents, 323 MGM, 205 MGF, 197 PGM and 128 PGF. Parents’ measures were collected when child was aged 5, and grandparents' at child’s birth. Data were again available for 568 children aged 5 and 298 at age 9. A mixed model analysis at 3 time points, adjusted for generation and age, produced correlations between family members.

RESULTS: At all three children's ages there were strong correlations with BMI of the mother and to a lesser extent the maternal grandmother, while for girls there was an association with the paternal grandmother at ages 0 and 5. There was an association also with father and his own mother. There were no evident associations with BMI of grandfathers. In contrast, height of the child was strongly associated with all family members at age 5, but at birth and age 9 only with the parents and paternal grandfather.

CONCLUSIONS: The results suggest that BMI is predominantly associated either with intrauterine development, or inherited through the X chromosome, or both, while height is a more complex trait, with genetic influences of parents and that of paternal grandfather persisting through to age 9.