Are there age differences in the association of genetic scores for BMI with BMI in Understanding Society?
Day:  Thu 4 Jul 
Time:  10:0010:30 
Room:  LTB5 

A large number of genetic variants are associated with body mass index (BMI). However the prevalence of obesity has increased rapidly in recent times. Thus, associations may have changed with the 20th century obesity epidemic. Our aim is to evaluate whether the magnitude of genetic associations with BMI vary in adults born later than earlier in the 20th century as these participants are exposed to the obesity epidemic at younger ages. A polygenic score for BMI (PGS), calculated as the weighted sum of alleles of 480 single nucleotide polymorphisms associated with BMI, with weights equal to the published perallele effects was used to examine age interactions with BMI examined across adult age range in Understanding Society. The PGS was associated with BMI (n = 8678; one standard deviation increase in PGS is associated with1.04kg/m2 increase in BMI, 95% confidence interval [0.929 1.145], P <.001, with mean age at first assessment, 53.3 years). The magnitude of associations of PGS with BMI were larger for younger age groups than older age groups (Estimate of interaction of age and PGS is 0.010 95%CI [0.017 0.004], Pint=0.002). For example, the associations of one standard deviation PGS increasing with BMI at age 25, 35, 45, 55, 65 and 75 are 1.33 [1.11 1.54], 1.22 [1.06 1.39], 1.12[1.00 1.24], 1.02 [0.91 1.12], 0.92[0.78, 1.05] and 0.81[0.63, 0.99] respectively. We conclude that PGS has strong effect on BMI in younger age groups than in older age groups.