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Applying Genetic Study Designs to Social and Behavioral Population Surveys
Pages 229-249

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From page 229...
... With the rapid advance of genetic knowledge and measurement technology, behaviorally oriented surveys may become important "laboratories" to seek genetic and other biological explanations for personal and social behaviors as well as to answer a broad range of scientific questions. It is also clear that such surveys will not lend themselves well to all possible scientific questions equally.
From page 230...
... This is followed by a review of genetic study designs and methods that could be applied to representative household surveys in order to address the contribution of genes and inheritance to disease etiology or progression and to age-related physiological and functional change. Finally, there is an overview of logistical considerations in approaching community-dwelling survey participants for specimen collection.
From page 231...
... Environmental observations are critical in their own right, but are often important cofactors for genetically related diseases and other outcomes. DEFINING THE PHENOTYPIC OUTCOMES IN POPULATION STUDIES All rigorously observed living things undergo age-related changes in physiology, metabolism, structure, and behavior.
From page 232...
... Survivorship and longevity, among the most widely studied attributes of aging across species, are insufficient outcomes for the study of complex animal processes, particularly in humans or other mammals; nearly all humans die of one or more discrete, identifiable medical conditions. Further, most if not all hypothesized biological mechanisms of aging encompass concepts that have also been applied to disease causation and progression.
From page 233...
... Broad survival traits in aging studies, such as longevity, active life expectancy, or rates of change in important age-related functional activities, are emblematic of this issue. Age-related disease outcomes, including most of the major chronic illnesses, are also extremely complex and difficult to define as homogeneous phenotypes.
From page 234...
... , but they have not fully resolved the role of inheritance in Parkinson's disease (Langston, 1998~. In general, most representative population surveys, even those of substantial size, do not contain sufficient numbers of twin pairs to conduct twin studies per se.
From page 235...
... using a variety of complex genetic study designs and models helps determine whether genetic markers are statistically linked to each other and are environmentally interactive as well. Most pedigrees containing an unusual occurrence of a particular disease or trait are not discovered in population surveys, but rather in the clinical setting.
From page 236...
... STUDY DESIGNS AND GENETIC BIOINDICATOR APPLICATIONS IN POPULATION STUDIES There are a substantial number of genetic study designs used to find associations between gene markers or gene function and health outcomes. If one includes all bioindicators that might be collected using simple techniques, such as from venipuncture or urine collection, there would be nearly limitless opportunities for associational studies between these indicators and health, functional, or other aging outcomes.
From page 237...
... However, other conditions such as ovarian cancer, Parkinson's disease, or even hip fracture, may not be suitably assessed in prospective population studies unless the sample size and the follow-up interval are large. One way to enhance the number of outcomes for genetic studies of diseases is to consider intermediate outcomes.
From page 238...
... The Intersection of Defined Survey Populations with Genetic Studies The following are some approaches to utilizing population-based cohorts for answering scientific questions related to genetics and health outcomes among older persons. Social science surveys are taking place in many countries, industrialized and developing, and the opportunities may be different according to the geographical locale and the prevalent environmental exposures and clinical conditions at hand.
From page 239...
... Founder Populations Some populations are chosen for special genetic study, particularly for complex genetic traits, because they are more genetically homogeneous than other populations, often because of social or geographic isolation over many generations. At least in theory, this may allow easier detection of gene-phenotype associations because there is less genetic "noise." Such approaches have several applications, such as in determining mutant mitochondrial DNA associated with dementia in a FrenchCanadian founder population (Chagnon et al., 1999)
From page 240...
... In the past most population genetic studies were designed, for reasons of efficiency, to evaluate candidate genes or gene markers selected for study based on prior linkage or associational methods, molecular or other studies, or on a priori reasoning. With 50,000-100,000 genes and wide allelic variation in the human genome and a much larger number of gene markers, including the potential to exploit the exact nucleotide sequence of the entire genome, it would seem difficult under the best of circumstances to determine and test all potential markers.
From page 241...
... Thus, there are many potential applications for population studies in the discovery and characterization of genes related to diseases and agerelated change. In the past, population studies were more effectively employed to verify if gene-disease associations found in pedigrees through the study of nuclear families were relevant to representative population groups, and to examine the clinical and public health implications of the associations.
From page 242...
... The following are some of the major considerations. The Impact of Specimen Collection on Survey Participation There is very little formally published information or synthesis on how specimen collection affects participation rates.
From page 243...
... Successful self-collection of DNA from oral epithelial cells has been reported (Harty et al., 2000~. However, there are other types of specimens that require more equipment or a medical setting to acquire, such as semen specimens, skin or adipose tissue biopsies, multiple blood specimens over many hours, or specimens collected in association with complex physiological testing.
From page 244...
... , steroid hormones (e.g., estrogen or testosterone) , and DNA, are relatively stable and can be profitably processed and stored (frozen)
From page 245...
... Alternative Sources for Genetic Bioindicators In some circumstances, such as when a potentially informative individual is deceased or otherwise not available for genetic study, it may be possible to acquire genetic or other bioindicator specimens from alternative sources. As noted by Martin and Hu in this volume, stored tissue specimens on which genetic or other determinations can be performed may be archived in hospitals or pathology laboratories.
From page 246...
... This is one justification for routine collection of DNA at the start of panel studies at an age when most participants are still available for study. CONCLUSION Substantial opportunities exist for important scientific contributions when specimen collection for genetic and environmental bioindicators is applied to existing or planned representative population surveys originally intended for behavioral, social, or economic purposes.
From page 247...
... Gauvreau 1999 Phylogenetic analysis of the mitochondrial genome indicates significant differences between patients with Alzheimer's disease and controls in a French-Canadian founder population. American Journal of Human Genetics 85:20-30.
From page 248...
... 1993 1992 American Society of Human Genetics presidential address: Back to the future. American Journal of Human Genetics 53:6-15.
From page 249...
... 1997 The potential of population surveys for genetic studies.


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