Meta-analyses of the relation between silicone breast implants and the risk of connective-tissue diseases.

Background: The postulated relation between silicone breast implants and th e risk of connective-tissue and autoimmune diseases has generated intense m edical and legal interest during the past decade. The salience of the issue persists, despite the fact that a great deal of research has been conducte d on this subject. To provide a stronger quantitative basis for addressing the postulated relation, we applied several techniques of meta-analysis tha t combine, compare, and summarize the results of existing relevant studies. Methods: We searched data bases and reviewed citations in relevant articles to identify studies that met prestated inclusion criteria. Nine cohort stu dies, nine case-control studies, and two cross-sectional studies were inclu ded in our meta-analyses. We conducted meta-analyses of the results of thes e studies, both with and without adjustment for confounding factors, and a separate analysis restricted to studies of silicone-gel-filled breast impla nts. Finally, we estimated the annual number of new cases of connective-tis sue disease that could be attributed to breast implants. Results: There was no evidence that breast implants were associated with a significant increase in the summary adjusted relative risk of individual co nnective-tissue diseases (rheumatoid arthritis, 1.04 [95 percent confidence interval, 0.72 to 1.51]; systemic lupus erythematosus, 0.65 [95 percent co nfidence interval, 0.35 to 1.23]; scleroderma or systemic sclerosis, 1.01 [ 95 percent confidence interval, 0.59 to 1.73]; and Sjogren's syndrome, 1.42 [95 percent confidence interval, 0.65 to 3.11]); all definite connective-t issue diseases combined (0.80; 95 percent confidence interval, 0.62 to 1.04 ); or other autoimmune or rheumatic conditions (0.96; 95 percent confidence interval, 0.74 to 1.25). Nor was there evidence of significantly increased risk in the unadjusted analyses or in the analysis restricted to silicone- gel-filled implants. Conclusions: On the basis of our meta-analyses, there was no evidence of an association between breast implants in general, or silicone-gel-filled bre ast implants specifically, and any of the individual connective-tissue dise ases, all definite connective-tissue diseases combined, or other autoimmune or rheumatic conditions. From a public health perspective, breast implants appear to have a minimal effect on the number of women in whom connective- tissue diseases develop, and the elimination of implants would not be likel y to reduce the incidence of connective-tissue diseases. (N Engl J Med 2000 ;342:781-90.) (C)2000, Massachusetts Medical Society.