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Supplementary Material for: The Positive Association of Obesity Variants with Adulthood Adiposity Strengthens over an 80-Year Period: A Gene-by-Birth Year Interaction

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posted on 27.09.2013, 00:00 by Demerath E.W., Choh A.C., Johnson W., Curran J.E., Lee M., Bellis C., Dyer T.D., Czerwinski S.A., Blangero J., Towne B.
Objective: To test the hypothesis that the statistical effect of obesity-related genetic variants on adulthood adiposity traits depends on birth year. Methods: The study sample included 907 related, non-Hispanic White participants in the Fels Longitudinal Study, born between 1901 and 1986, and aged 25-64.99 years (474 females; 433 males) at the time of measurement. All had both genotype data from which a genetic risk score (GRS) composed of 32 well-replicated obesity-related common single nucleotide polymorphisms was created, and phenotype data [including body mass index (BMI), waist circumference, and the sum of four subcutaneous skinfolds]. Maximum likelihood-based variance components analysis was used to estimate trait heritabilities, main effects of GRS and birth year, GRS-by-birth year interaction, sex, and age. Results: Positive GRS-by-birth year interaction effects were found for BMI (p < 0.001), waist circumference (p = 0.007), and skinfold thickness (p < 0.007). For example, each one-allele increase in GRS was estimated to result in a 0.16 increase in BMI among males born in 1930 compared to a 0.47 increase among those born in 1970. Conclusions: These novel findings suggest the influence of common obesity susceptibility variants has increased during the obesity epidemic.