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What
is epidemiology good for?
Epidemiology
provides a scientific basis for preventing or ameliorating disease
and disability on a population basis. Table 5.1 lists eight types
of scientific and public health research activities encompassed
in epidemiologic investigation (Morris,
1975; Von
Korff et al., 1992a).
Table
6.1 Uses of Epidemiology as Applied to TMD Pain
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Establishing the dimensions of morbidity and mortality
as a function of person, place and time. | A
survey to determine the percent of adults in the non-institutionalized
civilian US population with “pain more than once
in the jaw joint or in front of the ear” and to
determine prevalence rates by age, gender and geographic
area (Lipton
et al., 1993). |
| Quantifying
risks of developing morbidity as a function of host,
agent and environmental factors. | A
study examining whether age, gender, depression and
number of other pain conditions at baseline predict
the onset of TMD pain over a 3-year period among persons
in a population sample (Von
Korff et al., 1993). |
| Identifying
and defining syndromes | A
study examining whether risk factors are similar of
different for persons with: a) myofascial pain only,
b) myofascial pain plus arthralgia, and c) arthralgia
only (Huang
et al., 2002). |
| Describing
the full clinical spectrum of disease | A
study comparing examination findings in people who seek
treatment for TMD, those who have TMD pain but are not
seeking treatment and controls (Dworkin,
et al., 1990a). |
| Describing
the natural history of disease in terms of onset, duration,
recurrence, complications, disability and mortality | A
study reporting the rate of onset (and offset) of TMD
pain on active opening or lateral and forward movement
of the lower jaw in a population of adolescent girls
over a 5-year period (Kitai,
et al., 1997). |
| Identifying
factors that influence or predict clinical course | A
longitudinal study of baseline predictors of myofascial
pain at 1-, 3- and 5-year follow up (Rammelsberg,
et al., 2003). |
| Identifying
causes of disease, disability and mortality | A
study examining the rate of use of hormone replacement
therapy in women over 40 years of age with and without
TMD (LeResche,
et al., 1997). |
| Evaluating
methods of disease prevention and control | A
randomized clinical trial to assess the effectiveness
of a structured program of self care for reducing ongoing
pain and muscle palpation pain in patients with TMD
pain and low life interference (Dworkin
et al., 2002a). |
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Although an
epidemiologic study can address more than one of these issues,
i.e. can be useful in multiple ways, it is important to keep in
mind the primary purpose when designing a study. Is the main purpose
to enumerate cases and identify treatment needs in order to set
national health care priorities, or is the primary aim to study
the etiology of the condition? These two purposes could result
in very different study designs (see Section
4.0, Choosing an Appropriate Study Design).
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