Breast Implants


Do Breast Implants Cause Disease:
A Review of the Studies Included in the Recent Meta-Analysis
By Patricia Lieberman, Ph.D. and Diana Zuckerman, Ph.D.
There are 20 epidemiological studies included in the meta-analysis
published in the New England Journal of Medicine (March 16, 2000), to
determine whether breast implants cause connective-tissue diseases. This is
essentially the same meta-analysis that was conducted by Judge Pointer’s
scientific panel. The authors concluded that the studies show no association
between silicone breast implants and connective-tissue disease. A careful
review of the studies included in the meta-analysis reveals that those
studies have a number of flaws.
Five of 20 studies cited were not published in peer-reviewed journals.
Instead they were papers presented at scientific meetings or unpublished
doctoral dissertations. There was therefore limited information on
methodology available to evaluate the validity of the study designs.

The studies do not provide a comprehensive evaluation of diseases among
breast implant patients. Most evaluate a few connective-tissue diseases,
including such rare diseases as scleroderma. Most do not evaluate the
"atypical" connective-tissue disease symptoms or fibromyalgia-type symptoms
that many patients report.

Even for the illnesses that they evaluate, the studies have limitations. In
order to conduct an accurate study of implant patients’ health, patients
should undergo a comprehensive medical exam. In contrast, most of these
studies relied on medical records, which might omit vague symptoms that
would be reported in the early stages of disease. Several studies relied on
self-report, but only the one that found a significant risk due to implants
was criticized because patients might exaggerate their health problems. In
contrast, studies that determined whether women had implants based on
self-report were included and not criticized as biased, even though it would
be expected that some women would fail to mention that they have implants.
This failure to report implants is especially likely when information was
gathered in person or on the telephone, rather than in a questionnaire.

Several of the studies relied on hospital records. Very few implant patients
would have been hospitalized for their symptoms, since most health problems
that implant patients have reported do not require hospitalization.

The studies included women who had implants for a short period of time, such
as a few months or years. If implants cause connective-tissue diseases, it
would be expected that the disease would develop over a period of years.
Diseases might also be more likely after a silicone gel implant breaks,
which usually occurs after 7-10 years. Therefore, a well-designed study
would include women who had implants for at least 7-10 years, not an average
of 7-10 years.

Many of the studies do not evaluate the safety of implants for mastectomy
patients, and therefore the results may not be relevant to them.

Many of the samples are too small to study rare diseases, and thus, have
limited power to detect increases in the rates of disease, even increases as
large as 50-100 percent.

Older implants (from 1964-75) were made of a thicker silicone shell than
newer implants. Those implants were less likely to "bleed" silicone through
the shell or to break. Therefore, studies with women who had implants for a
wide range of years would not be expected to show a "dose" response, and
studies with women having implants for an average of 7-10 years often
include many women with implants for very short periods and women with these
thicker, potentially less damaging, implants. That minimizes the likelihood
of results showing significant risks from implants.

In at least one of the studies, women were included in study even if they
had their breast implants removed shortly after they got them. It is
impossible to tell from that study how long the women had breast implants.
The other studies do not mention whether women who were identified by
medical records as having implants still had them years later. Those
omissions potentially bias the findings because women who had implants
removed do not have the same amount of exposure as women who have implants
continuously.

COHORT STUDIES

Cohort studies compare women with breast implants to a group of women
who are similar in terms of age, race, and health who did not have breast
implants.

Edworthy, S.M., Martin, L., Barr, S.G., et al. A Clinical Study of the
Relationship Between Silicone Breast Implants and Connective Tissue Disease.
Journal of Rheumatology 1998; 25: 254-260.

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