Objective: To investigate the joint role of the 48-base pair repeat polymorphism of the dopamine receptor 4 gene (DRD4) and environmental factors in body mass variation among an ethnically diverse sample of U.S. adolescents and young adults.
Research methods and procedures: Approximately 2600 adolescent and young adults in the National Longitudinal Study of Adolescent Health (Add Health) who provided DNA measures and measures of height and weight were included in the analysis. Mixed regression modeling was used to investigate the effects of the 7R/7R and any5R variants in the DRD4 gene simultaneously with the effects of physical activity (PA), sedentary behavior (SB), and family socioeconomic status (SES) on body mass variation. European Americans, African Americans, and Hispanic Americans were modeled separately.
Results and discussion: Both the 7R/7R and any5R genotypes of the DRD4 gene were associated with age- and sex-specific BMI percentile score (BMI-P) based on the Centers for Disease Control and Prevention/National Center for Health Statistics 2000 reference curves among African Americans and only among African Americans (N = 413) 20 years old or younger. Neither genetic variants are associated with the BMI measure among white (N = 1386) and Hispanic-American (N = 331) adolescents. The presence of the 7R/7R genotype was associated with a reduction of 15.1 in BMI percentile (p = 0.005), and the presence of any5R was associated with an increase of 15.5 in BMI percentile (p = 0.003), after adjusting for PA, SB, and family SES. Neither PA nor SB as measured in Add Health is importantly associated with BMI-P, suggesting a complex relationship between body mass and PA/SB among adolescents and young adults. Family SES is negatively related to BMI-P in the European-American sample.