Cells and Surveys Should Biological Measures Be Included in Social Science Research? (2001) / Chapter Skim
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Biological Material in Household Surveys: The Interface Between Epidemiology and Genetics
Biological Material in Household Surveys: The Interface Between Epidemiology and Genetics
Pages 42-63
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From page 42... ...
The collection of biological material in sizeable household surveys could provide a sound basis for future gene-environment interaction studies. The inclusion of biological material in household surveys can also improve information about environmental factors usually studied by epidemiologists, such as diet and exposure to heavy metal compounds and pesticides.
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From page 43... ...
If there is no strong evidence that genetic factors play a role in the variation in a number of important traits, there seems to be little reason to undertake the logistic and ethical challenge of including genetic material in household surveys. Twin and adoption studies can estimate the overall genetic influence on a given trait, while other kinds of family studies are not very well suited to disentangle the effects of genes and common environment.
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From page 44... ...
For continuous traits, intraclass correlations are used instead of concordance rates. The twin study does not identify specific genes that affect a given trait, but rather, assesses the overall effect of genetic factors: the degree to which differences in the phenotype are attributable to genetic differences between people.
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From page 45... ...
Below is a description of recent twin studies of particular interest to demographers and social scientists.
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(1999) studied the genetic dispositions influencing fertility and fertility-related behavior using Danish twins born in the period 1870-1964.
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From page 47... ...
Genetic effects were most pronounced in periods with consciously controlled fertility, suggesting that the genetic disposition primarily affects fertility behavior and motivation for having children. Analyses of fertility motivation in some of the more recent twin cohorts, measured by age at first attempt to have children, supported this interpretation.
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From page 48... ...
Dementia has a very strong genetic component, not only with regard to early-onset monogenic types but also to late-onset dementia (Breitner et al., 1993; Gatz et al., 1997~. Alternatively, twin studies provide little evidence of genetic factors in the etiology of Parkinson disease (Tanner et al., 1999~.
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From page 49... ...
The most promising aspect emerging from the identification of specific genes influencing various traits is that this may be the basis for insight into the underlying biological processes and, in particular, how genes interact with the environment. An understanding of such gene-environment interactions can lead to environmentally based prevention or treatment of unwanted conditions or diseases with a strong genetic component, as described in the next section.
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From page 50... ...
It seems likely that APOE e4 is just one of many common genetic variants in the estimated 50,000 to 100,000 genes in the human genome that increase susceptibility for environmental exposures. Design Options for Gene-Environment Interaction Studies Within Household Surveys Within the framework of a household survey, there are two major design options for studying gene-environment interactions: the cohort study and the so-called "nested case-control study." Cohort Studies This design uses the entire study population of persons at risk for the outcome of interest and follows this cohort over time.
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From page 51... ...
From the frequencies of the gene variants in the case and the control group, the odds ratio can be estimated, which is approximately equal to the relative risk associated with an allele if the outcome studied is not too common (i.e., less than 5 percent of the population studied will get the disease/ condition)
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From page 52... ...
example, in medically oriented surveys, cognitive abilities and depression symptomatology can be assessed, but a dementia or depression diagnosis according to internationally recognized criteria can be obtained only in follow-up studies with the assessment done by specialists. The biggest challenge to gene-environment interaction studies in the years to come will probably be a multiple comparison problem.
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From page 53... ...
FEASIBILITY OF COLLECTING BIOLOGICAL MATERIAL IN HOUSEHOLD SURVEYS The Danish 1995-1999 Experience Since 1995 our group at The Aging Research Center at the University of Southern Denmark and the Danish Center for Demographic Research has conducted six major surveys: The Longitudinal Study of Aging Danish Twins (three waves in 1995, 1997, and 1999, respectively: LSADT-95, LSADT-97, LSADT-99) , The Longitudinal Study of Middle-Aged Twins, The Danish 1905-Cohort Survey, and The Danish Centenarian Study, together comprising more than 10,000 individuals.
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From page 54... ...
The Longitudinal Study of Middle-Aged Twins To complement the LSADT studies with a twin study of middle-aged twins, we identified a random sample of twin pairs born between 1931 and 1952 through the Danish Twin Registry (Kyvik et al., 1996; Skytthe et al., 1998~. In 1999, more than 5,000 twins aged 46-67, including monozygotic twins and fraternal twins of same and opposite sex, were invited to participate in an extensive face-to-face interview conducted by lay interviewers, which included tests of physical and cognitive function.
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From page 55... ...
The LSADT studies have response rates of 72-79 percent, which many regard as very good for extensive surveys among the elderly (Table 3-1~. The best way to estimate the participation cost of including biological material in an ongoing survey is to compare the 1997 (no biological sampling)
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From page 56... ...
How to Obtain DNA from the Participants by Means of a Finger Prick and Cheek Brushes The same procedure for DNA sampling was used in The Danish 1905Cohort Study, The Danish Middle-Aged Twins Study, and LSADT-99 without any notable logistic problems. In these investigations, participants were asked to donate a DNA sample in the form of a blood spot or, if they disliked the idea of blood spots, by means of cheek brushes.
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From page 57... ...
The blood spot cards are stored in boxes at room temperature. The utensil cost was $2-3 per person and the interview time averaged 5-10 minutes depending on age, but with large variation.
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From page 58... ...
58 BIOLOGICAL MATERIAL IN HOUSEHOLD SURVEYS FIGURE 3-6 To avoid sample loss, the blood spots are divided in two and kept in two different locations. FIGURE 3-7 Brushes used to obtain biological samples from the inner cheek in connection with household surveys.
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From page 59... ...
TABLE 3-2 Surveys Conducted at the Aging Research Center at the University of Southern Denmark and the Danish Center for Demographic Research in the Period 1998-1999, Which Included Collection of Biological Material by a Finger Prick or Cheek Brush Biological Samples % of Blood Cheek % of Nonproxy Spots Brushes Participants No. Participants Participants % % The 1905-cohort 2,262 1,632 72 90 80 20 LSADT-99 2,709 2,319 86 90 91 9 Middle-aged twins 4,314 4,171 97 97 95 5 TOTAL 9,285 8,122 87 93 93 7
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From page 60... ...
As mentioned, the biological samples are kept anonymously and apart from the information obtained during the interview, but the information is linkable through the participants' ID numbers. For quality control we have determined APOE gene variants on a subsample of the blood spots and the cheek brushes with a success rate of 99 percent.
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From page 61... ...
Holm, and J.W. Vaupel 2000b Genetic and environmental influences on functional abilities among Danish twins aged 75 years and older.
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From page 62... ...
Green, and N.H. Beck 1995 Concordance rates of insulin dependent diabetes mellitus: A population based study of young Danish twins.
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From page 63... ...
Eberle, and L Gurtler 1998 Detection of HIV 1 infection in dried blood spots from a 12 year old ABO bedside test card.
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