Specialized Settings of Epidemiology
I’m choosing to compare genetic and molecular epidemiology simply because I’m fascinated
with genetics in general. In general, genetic epidemiology is a discipline that seeks to unravel
the role of genetic factors -- and their interactions with environmental factors – in the etiology of
diseases, using family and population study approaches. Molecular epidemiology, in general, is
a science that deals with the contribution of genetic and environmental risk factors identified at
the molecular and biochemical level, to the etiology, distribution and control of disease in
families and populations.
Genetic Epidemiology
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Identify inherited factors that influence
disease
Identify how variation in genetic
material interacts with environmental
factors to increase or decrease risk of
disease (environmental factors matter)
Use family and population study
approach
Focus on genes and evidence for
genetic influences
Typically not interested in “mapping”
genes – more interested in how genes
interact with environment
a better understanding of genetic
etiology of disease can facilitate early
detection in high risk subjects
can help design more effective
intervention strategies
difference with genetic epidemiology is
that families are required for study
instead of independent subjects
this lack of independence necessitates
special rules in selection of subjects
and analytic approaches
Clustering of disease is NOT due to the
environment
Goal is to identify regions of DNA that
cosegregate (inherit in same patterns)
Includes identification of unknown
genes that influence risk of disease
cannot tell easily whether clustering of
Molecular Epidemiology
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Uses molecular markers (in addition to
genes) to establish exposure-disease
associations
Has greater precision in estimating
exposure-disease associations
Has possibility of providing early
warnings for disease by flagging
preclinical effects of exposure
Field is broader than genetic
epidemiology
Field includes a wide variety of biologic
measures of exposure and disease
Does not involve studies of biologically
related individuals
Most are conducted to evaluate the
significance of variation in genes that
would not necessarily manifest as
Mendelian patterns of disease in a
family
Evaluates the association of variation of
“known” genes with risk of disease
May use both positional
cloning/physical mapping and functional
cloning/mapping
Both cohort and case-control studies
can be used
Can readily employ retrospective
designs because genetic code is
unchanged from conception
Enhances understanding of
pathogenesis of disease
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a risk factor or disease within a family
is due to genetics, culture, or shared
environment (including social or
political factors)
Can utilize case-control studies, family
studies, twin studies, linkage analysis
(works well for diseases that follow
simple rules of inheritance – i.e.
autosomal dominant or recessive),
segregation analysis
Results are NOT generalizable to the
public at large
May utilize both functional and
positional cloning
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Defines genetic susceptibility with
molecular markers – not surrogate
information (i.e. family history)
 Improves validity and reduces bias for
assessment of environmental exposure
 Allows for evaluation of subclinical or
early disease markers
 Reduces heterogeneity in classification
of diseases in descriptive studies
 Provides new standards for descriptive
epidemiology
- Using molecular tests allow
diagnostic criteria employed to
identify cases of disease results
in more homogenous groups
 Improves precision in analytical
epidemiology
- Contribution of genetic and
environmental factors and their
interaction to the risk of
developing disease can be more
accurately assessed