NEW ALBANY, IN (Jan. 24, 2014) -Indiana University Southeast psychology professor Deb Finkel was recently featured in an interview with ElderBranch called “Nature vs. Nurture as it Impacts Cognitive Aging.” The following interview is also available at elderbranch.com.
“Nature vs. Nurture as it Impacts Cognitive Aging.”
By Jeanette Brown
Deborah G. Finkel, Ph.D., is a professor of psychology at Indiana University Southeast. In her research, she applies the methods of behavioral genetics to investigations of cognitive aging and biological markers of the aging process. She also applies the methods of longitudinal analysis to twin data to investigate genetic and environmental influences on longitudinal change.
ElderBranch interviewed Dr. Finkel to discuss her recently published article, “Sex Differences in Genetic and Environmental Influences on Longitudinal Change in Functional Ability in Late Adulthood,” which she wrote with Dr. Marie Ernsth-Bravell of Jönköping University’s School of Health Sciences and Dr. Nancy L. Pedersen of Karolinska Institute’s Department of Medical Epidemiology and Biostatistics.
What led you to research which genetic and environmental factors contribute to individual and gender differences in functional ability as people age? Why is this important? How does your current research augment other work in this area?
Ask anyone who is experiencing the aging process, and you’re likely to find two types of complaints: physical and mental. Changes in physical functioning and cognitive functioning are the two major components of the aging process.
I have spent decades investigating genetic and environmental influences on cognitive aging, but at the same time I was always interested in the other major component of the aging process. I have done some research on lung function and blood pressure, for example. But I have always wanted to examine the relationships between the two domains: do they age together? Does aging in one domain cause aging in the other domain?
Fundamentally, development and change can occur for two basic reasons: genetic influences and environmental influences – nature and nurture. We know that both are always involved, but we want to know how much. To what extent are the changes in physical function with age the result of genetically programmed senescence (which we can probably do little about) and to what extent are the changes the result of the accumulation of environmental factors (that we should be able to impact)?
Clearly, there are very important implications for interventions and successful aging. We all want to know what we can do to maximize the quality of our aging years.
Other researchers have investigated this question, of course. The innovation of our work includes: (1) 24 measures of day-to-day examples of physical functioning (such as getting up from a chair or putting a key in a lock) that were observed by nurses instead of relying on self-report and (2) 20 years of longitudinal follow-up of elderly twins. The Swedish Adoption/Twin Study of Aging (SATSA) allows us to examine not just changes in functioning within individuals, but changes in the genetic and environmental contributions to functioning over time.
Please describe your study. What were your methods? What were your in-going hypotheses?
Dr. Marie Ernsth-Bravell and I were able to reduce the 24 different measures of physical function to three factors that capture the nature of physical movement: fine motor movements (things we do with our hands), balance and gross motor movement (movements that engage the entire body), and flexibility.
Longitudinal twin data were available from 859 twins aged 50 to 88 at baseline. Statistical modeling allowed us to examine changes in average performance with age and genetic and environmental contributions to those changes.
In addition, given the evidence for sex differences in physical aging, we investigated the possibility of sex differences in genetic and environmental contributions to physical aging. Men and women in these generations experienced very different physical environments, perhaps to a greater extent than men and women today.
What were your key findings?
We found very different results for the three different types of physical functioning and different results for men and women.
- Most participants performed well on the measures of physical function up to age 65 or 70. Inability to perform the tasks only began to arise in late adulthood.
- Decline in fine motor movement was fairly steady and the same for men and women.
- The rate of decline in balance increased significantly after age 70 but showed the same pattern for men and women.
- Flexibility declined faster in women than in men.
- Increasing variance in the functional ability factors resulted largely from increases in environmental components of variance, including correlated and shared rearing environmental variance.
- The largest sex difference in genetic and environmental influences on physical functioning was found for the balance factor. Genetic variance is evident only for women, and this genetic variance increases after age 70. As a proportion of variance, however, standardized heritability estimates decrease from an average of 75 percent before age 70 to 55 percent after age 70. No evidence was found for genetic influences on balance in men.
What are the implications of your findings?
In general, women demonstrate slower aging trajectories on the majority of biological markers of the aging process, with the exception of measures that tap muscle strength or function. Women have less muscle mass to begin with and tend to lose muscle mass at a faster rate than men.
Moreover, women experience a higher prevalence of genetically influenced chronic disabling diseases compared with men’s more compressed history of disability before death. Thus, fundamental biological differences between men and women may contribute to the finding of significant genetic variance for functional ability in women and not in men.
What are the next steps to further your work?
Now that we have described genetic and environmental influences on longitudinal changes in physical functioning, the next step is to examine both cognitive and physical functioning in the same sample and address the issues of the relationship between the two.
Does aging in one domain cause aging in the other domain? Even more, we can ask whether genes that influence physical aging are also related to cognitive aging. Do physical and cognitive aging share a common genetic or environmental cause?
I have found, for example, the genes influencing age changes in lung function explain subsequent age changes in some cognitive abilities. The next step is to apply the same methodology to physical and cognitive aging.