Epidemiological principles for EMF and EMR studies - Lincoln ...

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Figure 2: The basic design of a cohort study, Beaglehole, Bonita and Kjellström
(1993).
By then investigating the rate of disease in the exposed group compared with the
rate of disease in the remainder of the group who were not exposed, the effect of
exposure can be evaluated. Initially it appears from Figure 1 that because both the
case- and control- groups are compared between exposed and not exposed groups
that the effect of exposure on the assumed not exposed group, could be being
dealt with. However, because there is a wide range of residential and urban levels
of exposures to the ELF & EMR fields, this can vary greatly from individuals and
groups. This produces significant confounders in these studies.
As it has demonstrated above, the failure to adequately deal with a ubiquitous
agent will place a proportion of the exposed group in the not exposed group and
grossly underestimate the effects of a disease agent. Hence a more appropriate
exposure assessment is vital.
When dealing with a ubiquitous agent such as electromagnetic fields and radiation,
adequate exposure assessment requires extensive understanding and the
development of careful methods. Otherwise, results will be very misleading through
underestimating the impact of the exposure and ignoring the exposure factors
within the control groups. An important factor in cohort studies is matching the
characteristics of the not exposed group as much as possible to those of the
exposed group so that the only difference is exposure, not age, sex, ethnicity nor
income for example.
Statistical Methods:
Even though Sir Austin said that significant statistics are not required for deciding a
causal relationship he agreed that they showed the play of chance and show the
magnitude of the RRs. Hence an appropriate use of statistical methods is helpful.
One-tailed and two-tailed distributions:
The normal statistical method uses a one-tailed distribution test for a one direction
effect and a two tailed test for a two directional effect. If you are seeking to
determine whether a disease agent is going to increase an incidence of the disease
then a one-tailed test is appropriate. If the influence of the agent is unknown then a