Inequalities in health outcomes are targeted by Healthy People 2020 as a public health priority. The social stratification of health is well documented, pervasive, and of growing concern because it appears to be increasing over time. Reducing these social class disparities will require greater understanding of how social class impacts health than we currently have. While most research focuses on individual-level socioeconomic status?defined as social status that accrues to occupational classification, education, and income?new research has begun to focus on the macro-economic environment. Further, although both genetic (G) and environmental (E) factors are known to contribute to the SES-health gradient, the mechanisms by which the two sets of factors combine to influence health outcomes (i.e., GE interplay) are poorly understood. Models of GE interplay differ in their environmental focus (disease-triggering effects of toxic environments vs. health- promoting benefits of favorable environments) and the expected genetic contribution to disease (maximized in adverse environments, in favorable environments, or at both extremes) Understanding whether high-SES preferentially promotes good health among a genetically selected subset of individuals (i.e., social enhancement), whether low-SES triggers poor health among a genetically vulnerable subset of individuals (i.e., diathesis-stress), or both, is essential for translating research in this area into effective prevention strategies. The consortium on Interplay of Genes and Environments across Multiple Studies (IGEMS) with 16 existing longitudinal twin studies in the U.S., Sweden, Denmark, Finland, and Australia is poised to evaluate these models. IGEMS includes more than 52,000 individual twins, with over 7000 identical twin pairs for within-pair difference models, and over 12,600 dizygotic twin pairs with nearly 4000 opposite sex pairs for sex-difference models. The sample spans a wide age range (15 to 103 years at intake) and includes a set of well-characterized longitudinal phenotypes, including harmonized measures of physical health (e.g., subjective health, chronic disease indicators, body mass index, lung function, blood pressure, activities of daily living, and grip strength), cognitive health (verbal ability, spatial ability, memory, and processing speed), and emotional health (depression, loneliness) as well as measures of multiple facets of SES (e.g., occupation, education, financial strain). In addition, a large subset of IGEMS participants has genome wide genotyping from which we have computed polygenic risk scores (PRS). We will use co-twin control/within pair models, quantitative genetic moderation, sex-limitation models, and PRS analyses to investigate specific mechanisms of the SES-health gradient at the individual level as well as the country and historical cohort level (e.g., country-level indices of social inequality). The proposed study reflects an innovative vision by the investigators who?rather than addressing the research questions through new data collection?successfully created a collaboration among 16 large international studies with relevant phenotypes, making this study highly cost-effective and efficient.

Public Health Relevance

The central goal of the proposed work is to gain a better understanding of how socioeconomic differences among individuals, including women and men, and within and across countries, affect diverse aspects of late- life functioning. Bringing together 16 longitudinal twin studies of aging, including rich genotype data on a large subsample, provides a powerful tool for teasing apart the roles of environmental risk and genetic vulnerability and their interplay in accounting for differential aging outcomes in physical, cognitive, and emotional health. Results will contribute to a clearer understanding of the mechanisms underlying health and disease and will allow anticipating the consequences of health and social policy for population health.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Project (R01)
Project #
5R01AG059329-03
Application #
9953943
Study Section
Social Sciences and Population Studies B Study Section (SSPB)
Program Officer
King, Jonathan W
Project Start
2018-09-01
Project End
2023-05-31
Budget Start
2020-06-15
Budget End
2021-05-31
Support Year
3
Fiscal Year
2020
Total Cost
Indirect Cost
Name
University of Southern California
Department
Psychology
Type
Schools of Arts and Sciences
DUNS #
072933393
City
Los Angeles
State
CA
Country
United States
Zip Code
90089