Epidemiology of silicone-related disease

The epidemiology of silicone-related disease (SRD) is complicated by the variety of disease endpoints that have been associated with silicone exposure and the atypical nature of these diseases in silicone-exposed women. Current research reviewed here suggests that SRD may constitute a new disease entity, thus complicating disease definition and rendering studies of classic disease unlikely to detect risks of silicone exposure. This report addresses the most important study design issues (disease and exposure definitions, bias, confounding, and power) in the context of studies of SRD. The variety of silicones used complicates the definition of exposure for all studies, and for some populations simply determining who was implanted will be difficult. For any of these studies, inadequate patient follow-up is likely to underestimate disease risk. Studies of SRD are also complicated by confounding. That is, whether or not a woman chooses to receive an implant is related to her age, race, and other variables also related to rheumatoid and autoimmune disease. The absence of an appropriate control group also plaques published studies of silicone-related disease. Finally, inadequate sample size, resulting in studies of low statistical power, is a critical problem for rare diseases such as SRD. These points are illustrated using two published studies and five studies in progress.