ETIOLOGY OF BMI TRAJECTORIES ACROSS ADULTHOOD IN TWO COHORTS

Variation in BMI is largely explained by increasing genetic influences across adulthood, and with possibly amplified genetic influences in later born cohorts. We evaluated genetic and environmental influences on BMI trajectory features across the adult lifespan, including the impact of polygenic risk scores (PRS) in twins from the Swedish Twin Registry enrolled in TwinGene or SATSA. BMI trajectories with turning points at 65 and 80 years were fitted for two birth cohorts (before 1926, 1926 and later). Genetic variance was greater across age for the later born cohort with higher heritability for BMI level at age 65 (67–79% vs 52–65%) and generally lower heritability for linear change after age 65. Similarly, PRS explained more variation in BMI across age for the later born cohort (e.g., 4% vs 2% for variants at p=1E-05), but with differences by age period and sex. Etiological influences differ by age, sex, and cohort.