The long arm of the family: are parental and grandparental earnings related to young men's body mass index and cognitive ability?

BACKGROUND: The lasting impact of parents' socioeconomic status on their children's social trajectories and health is well-established, but do such intergenerationally transmitted inequalities persist also into the third generation? This study investigates the importance of parental and grandparental earnings for young men's body mass index (BMI) and cognitive ability at military conscription.
METHODS: The database used was UBCoS Multigen, which combines existing data on an Uppsala cohort born 1915-29 with information on several subsequent generations. We analysed young men in the third generation with complete information about the earnings of paternal (n = 3577) and maternal (n = 4142) ancestors of the two preceding generations using OLS-regression.
RESULTS: On the paternal side, father's and grandfather's, but not grandmother's, earnings predicted cognitive ability and BMI. In the mutually adjusted models, the associations with cognitive ability largely remained for young men whose fathers [b = -0.96 (95% CI: -1.25, -0.66)] and grandfathers [b = -0.60 (-0.87, -0.33)] were poor rather than well-off, whereas for BMI, only the association with grandfather's earnings [b = 0.78 (0.37, 1.19)] persisted. On the maternal side, the mutually adjusted models indicated that the mother's [b = -0.89 (-1.14, -0.65)] and the grandfather's [b = -0.65 (-0.89, -0.41)], but not the grandmother's, earnings were predictive of cognitive ability, whereas only the grandfather's [b = 0.56 (0.18, 0.94)] earnings seemed to be important for BMI.
CONCLUSIONS: The results suggest that the long arm of the family reaches beyond the second generation in its effect on health. Although this study has only scratched the surface of how health inequalities is reproduced, it suggests that policies that reduce social inequalities may have ramifications across several generations.