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A
fundamental objective of epidemiology is to produce knowledge
relevant to disease prevention and control. Repeatedly, epidemiologic
research has identified methods of disease prevention or control
before the etiologic mechanisms of the disease were firmly established.
The clinical
trial is a rigorous means of evaluating methods of disease control,
while the preventive trial provides methods of evaluating the
efficacy and effectiveness of promising methods of preventing
the onset of the condition.
Preventive
and clinical trials are essentially prospective cohort studies
in which exposure to a disease prevention or disease control measure
is randomly allocated. An excellent text by Meinert
(1986) provides a complete discussion of the methods of the
clinical trial. A review of clinical trial design in TMD can be
found in Chapter 22 of
this interactive textbook.
Example
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know of no preventive trials for TMD. The following
example comes from the literature on back pain.
Daltroy
et al. (1997) carried out a preventive trial to
determine whether an educational program designed
to prevent low back injury would reduce work loss
due to back pain among 4000 postal workers. The investigators
randomly assigned work units with about half the postal
workers and their supervisors to receive a two session
training program. The control workers and their supervisors
received no training. There were 21.2 back injuries
per person year at risk over a 5.5-year follow-up
period. The median time off work was 14 days and the
median health care cost of an injury was $204.
Although
workers’ knowledge of safe behavior was increased
by the training program, injury rates did not differ
for workers receiving the educational program and
the control workers. There were also no differences
in the median cost per injury, time off work per injury,
or the rate of repeat injury after return to work.
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