Genetic and Environmental Contributions to the Relationship between Cognitive and Physical Function
Open Access
- Author:
- Vasilopoulos, Terrie
- Graduate Program:
- Biobehavioral Health
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- August 24, 2009
- Committee Members:
- George Patrick Vogler, Dissertation Advisor/Co-Advisor
Jenae Marie Neiderhiser, Committee Member
David John Vandenbergh, Committee Member
Gerald Eugene Mc Clearn, Committee Member
George Patrick Vogler, Committee Chair/Co-Chair - Keywords:
- biomarkers
pulmonary function
grip strength
blood pressure
quantitative genetics
twins
aging - Abstract:
- While many studies have investigated the relationship between cognition and biomarkers of health, few have examined the etiology underlying this relationship. Both cognition and biomarkers of physical health, such as blood pressure, grip strength and pulmonary function, are complex traits, influenced by both genes and environments. They are also dynamic traits, with the contributors to their variances changing across time. The purpose of this dissertation was to evaluate to what extent cognitive function and physical function share genetic and environmental influences and how these genetic and environmental factors contribute to changes in cognitive function and physical function over time. The first study evaluated to what extent cognitive function and physical function share genetic and environmental influences and to what extent are these influences unique to each phenotype. Through quantitative genetic modeling, a common phenotype was revealed to underlie the relationship between cognitive function and two biomarkers of physical health: grip strength and pulmonary function. The majority of the variance in this common phenotype was accounted for by genetic factors. This common phenotype, though, did not load onto two other physical health measures, systolic and diastolic blood pressure. However, these blood pressure measures were moderately correlated with the common factor that included cognitive function. The second study examined to what extent sex influences the quantitative genetic relationship between cognitive function and both grip strength and pulmonary function. Across several cognitive domains, the covariation between cognitive function and these two biomarkers differed between sexes. This difference was also evident in measures of longitudinal change for each trait. The final study incorporated APOE e4 allele status as a moderator in a quantitative genetic model of the covariation between blood pressure and cognitive ability, and the longitudinal relationship between these traits. APOE e4 allele status significantly moderated environmental pathways. Specifically, the amount of environmental variance in each trait, and the environmental covariance between blood pressure and cognitive ability, was greater in APOE e4 carriers, suggesting that the relationship between blood pressure and cognitive function is more sensitive to environmental factors in the presence of the APOE e4 allele. This study also presented a useful tool in integrating measured genotypes into quantitative genetic models. This technique provides a way to quantify the influence of both measured genetic and environmental factors on the quantitative variation of complex traits. The findings of this research shed light on how genetic and environmental factors contribute to the relationship between cognitive ability and physical function. Moreover, these findings support the need for more research to uncover what underlying phenotypes may be contributing to this relationship and to evaluate how specific genes and environments interact to influence the relationship between cognitive ability and physical function.