The epidemiology of systemic sclerosis: A population-based case-control study.

Abstract

Systemic sclerosis (SSc), or scleroderma, is a fibrosing connective tissue disease of unknown etiology and poor prognosis. The objective of this study was to ascertain the relationship between exposures to silicone and silica, plus certain environmental and lifestyle risk factors, and the development of scleroderma. This was accomplished by conducting a population-based case-control investigation of Michigan women. Cases were identified from several sources: a comprehensive hospital discharge diagnosis database, outpatients seen at the University of Michigan hospitals, patients of a scleroderma specialist and co-investigator, patients of rheumatologists and members of the United Scleroderma Foundation. Once identified, the medical records of consenting patients were reviewed to confirm the diagnosis and date of onset of disease. There were 377 eligible cases and 1184 controls interviewed by telephone. Eligible cases were defined as those women 18 years and older who were first diagnosed between January 1, 1980 and December 31, 1991 while living in Michigan. Women who left the state after diagnosis were considered eligible for participation. For those women who had expired, informed consent was sought from a family member. Female controls were selected using random digit dialing and were frequency matched to the cases on age, race and geographic region. Extensive analysis of the questionnaire data was conducted on a subgroup limited to the 1184 controls and 274 cases diagnosed between 1985 and 1991, inclusive. The case population was refined to reduce heterogeneity among cases and reduce potential selection and exposure biases. While no association to SSc was found for silicone or silica exposure, nineteen significant risk factors associated with scleroderma were identified. Four of these predictors were related to the heritability of disease indicating a familial disposition to SSc. Protective associations to scleroderma were found for activities involving grinding, having an implanted fixation device, using oral contraceptives and being diagnosed with hypertension. Chlorinated solvents and certain jobs and hobbies which may involve solvents were found to be positively associated with scleroderma.