The most definitive study yet of the health effects of silicone breast implants has found no association between the implants and connective tissue diseases.
The new study is so compelling and its results so consistent with previous studies, some leading rheumatologists contend, that the issue of whether implants cause those diseases can be considered closed. They maintain that it is time for the Food and Drug Administration to lift the voluntary moratorium on sales of the implants, which it requested in 1992.
Other doctors contend that the new study, like those that preceded it, is flawed. They say silicone breast implants are causing a new and ill-defined disease that has not been detected in epidemiological studies.
Donald McLearn, an FDA spokesman, said the agency was not ready to make a decision. He said the FDA was "encouraged that research is beginning to provide the kind of data that was lacking in the early 1990s."
But he added that the studies to date "cannot rule out a small but significant increase in risk" and that they do not "fully answer the question of whether the implants might lead to atypical symptoms related to the immune system in some women."
The latest study, by epidemiologists and rheumatologists at Harvard Medical School, Brigham and Women's Hospital, and the Harvard School of Public Health, all in Boston, is being published today in the New England Journal of Medicine. The study was financed by the National Institutes of Health.
The researchers studied 87,501 nurses, 1,183 of whom had implants. Dr. Graham A. Colditz, an epidemiologist at Harvard who is an author of the report on the study, said it began in 1976 as a long-term effort to investigate factors that affect health.
The researchers had the nurses' medical records and questionnaires the nurses had filled out over the years, enabling them to trace the women's medical histories. They analyzed data from June 1976 through May 1990, before an avalanche of lawsuits over purported links between silicone breast implants and connective tissue diseases.
The investigators found that women with implants were, if anything, slightly less likely to develop connective tissue diseases such as rheumatoid arthritis, or even to complain of signs and symptoms of disease that resembled those of connective tissue diseases but fell short of meeting the standard diagnostic criteria.
Thousands of women are suffering from fatigue and aches and pains, and believe that implants are responsible, but the proof from medical studies has been lacking.
Several previous studies found no links between implants and specific diseases, including scleroderma and rheumatoid arthritis. Another study, by researchers at the Mayo Clinic in Rochester, Minn., found no evidence that women with implants had developed any specific connective tissue disease.
Dr. Colditz said he and his colleagues conducted the study in response to growing public alarm over a possible link between implants and connective tissue diseases. In 1992, when the FDA requested the voluntary moratorium on the sale of silicone breast implants, it said the information available was not sufficient to show that they were safe.
At that time, some women with implants had developed connective tissue diseases, including rheumatoid arthritis, lupus and scleroderma, but there was no proof that the implants had caused the diseases. The agency asked the implant manufacturers to limit sales of the devices to women who needed reconstruction of a breast and agreed to participate in a clinical trial.
Although the FDA was careful to say there was no scientific evidence linking implants and connective tissue diseases, the moratorium fueled the litigation. In the past few years, tens of thousands of women have attributed their illnesses to the implants.
The illnesses usually did not fit he standard definitions of connective tissue diseases, but the women's doctors and lawyers said the implants had caused not only classic connective tissue diseases, but also a new sort of disease, with symptoms resembling those of standard diseases but not quite fulfilling standard diagnostic criteria.
Since then, implant manufacturers have entered into a $4 billion settlement of a class action suit brought on behalf of women with implants. More than 400,000 women have registered for the class action.
So many women have made claims that each can expect a small fraction of what had been promised, raising questions about the future of the settlement.