The Role of Genes
A related portion of this study will look for the relationship between depression, memory problems, and the presence of a gene. To carry out this part of the study, participants who were willing brushed the inside of their cheek with a swab from which DNA can be obtained. The results from the DNA test for the presence of ApolipoproteinE (APOE), or other genes, will be compared to information gathered in the Spectrum I study. The presence of this gene, the symptoms of depression, and the loss of memory will be analyzed. We hope to gain an understanding of how the presence of the gene overlaps with symptoms of depression and the on–set of reduced mental ability.
The APOE gene was selected for study because it has been associated in the past with diminished performance on neurological tests, cognitive impairment, and with abnormal use of glucose within the brain. Cognitive impairment is important because it is more common than dementia, casues disability and does, in some cases, lead to dementia.
ApolipoproteinE (APOE) plays an important role in lipid metabolism within the body. There are three major forms of this gene that contribute to the types of cholesterol (VLDL, LDL – bad cholesterol; HDL – good cholesterol) as well as the quantity of these cholesterol components in body tissue. The presence of one of the three major forms, e4, increases the chance of higher levels of LDL cholesterol (bad) and, thus, the chance for cardiovascular disease.
This study is comparing the presence of this form of APOE with the total symptom count for impairment in the quantitative data collected to the cognitive decline of the individual over the three–year period of the study. By comparing a combination of specific depressive symptoms with the presence of this APOE component to identify a group at risk for cognitive impairment, the opportunity for early treatment increases.
An interesting finding from this work on APOE data collection is that most people from the study group were willing to participate when the details were explained fully although persons over age 80 were less likely to wish to be included in the study. Many people have a limited understanding of genetics and a brief example proved helpful. A clear explanation was given to each person:
- What they are being asked to do.
- What will happen to the specimens.
- What information they provide after the study is complete.