title: Cohort of birth modifies the association between FTO genotype and BMI.
abstract: A substantial body of research has explored the relative roles of genetic and environmental factors on phenotype expression in humans. Recent research has also sought to identify gene-environment (or g-by-e) interactions, with mixed success. One potential reason for these mixed results may relate to the fact that genetic effects might be modified by changes in the environment over time. For example, the noted rise of obesity in the United States in the latter part of the 20th century might reflect an interaction between genetic variation and changing environmental conditions that together affect the penetrance of genetic influences. To evaluate this hypothesis, we use longitudinal data from the Framingham Heart Study collected over 30 y from a geographically relatively localized sample to test whether the well-documented association between the rs993609 variant of the FTO (fat mass and obesity associated) gene and body mass index (BMI) varies across birth cohorts, time period, and the lifecycle. Such cohort and period effects integrate many potential environmental factors, and this gene-by-environment analysis examines interactions with both time-varying contemporaneous and historical environmental influences. Using constrained linear age-period-cohort models that include family controls, we find that there is a robust relationship between birth cohort and the genotype-phenotype correlation between the FTO risk allele and BMI, with an observed inflection point for those born after 1942. These results suggest genetic influences on complex traits like obesity can vary over time, presumably because of global environmental changes that modify allelic penetrance.
authors.affiliation: Department of Psychiatry, Massachusetts General Hospital, Boston, MA 02114; JRosenquist@partners.org.
authors.forename: James Niels
authors.initials: JN
authors.lastname: Rosenquist
authors.affiliation: School of Policy Studies and Department of Economics, Queens University, Kingston, Ontario, Canada K7L 3N6; National Bureau of Economic Research USA, Cambridge, MA 02138;
authors.forename: Steven F
authors.initials: SF
authors.lastname: Lehrer
authors.affiliation: The Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine, Dartmouth College, Hanover, NH 03755;
authors.forename: A James
authors.initials: AJ
authors.lastname: O'Malley
authors.affiliation: Department of Health Care Policy, Harvard Medical School, Boston, MA 02115;
authors.forename: Alan M
authors.initials: AM
authors.lastname: Zaslavsky
authors.affiliation: Psychiatric and Neurodevelopmental Genetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114;
authors.forename: Jordan W
authors.initials: JW
authors.lastname: Smoller
authors.affiliation: Department of Sociology, Yale University, New Haven, CT 06520; Department of Medicine, Yale University, New Haven, CT 06520; Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520; and Yale Institute for Network Science, Yale University, New Haven, CT 06520.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Christakis
mesh_terms: D000328:Adult; D000071516:Alpha-Ketoglutarate-Dependent Dioxygenase FTO; D015992:Body Mass Index; D015331:Cohort Studies; D005260:Female; D005787:Gene Frequency; D059647:Gene-Environment Interaction; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D008957:Models, Genetic; D009765:Obesity / Q000453:epidemiology* / Q000235:genetics / Q000473:pathology; D011506:Proteins / Q000235:genetics*; D014481:United States / Q000453:epidemiology
chemical_list: D011506:Proteins; D000071516:Alpha-Ketoglutarate-Dependent Dioxygenase FTO; C526492:FTO protein, human
keywords: birth cohort; obesity; population genetics