A population-based case-control study risk factors for connective tissue diseases

Abstract

This dissertation describes the results of a population-based case-control study of risk factors for five connective tissue diseases: systemic lupus erythematosus, Sjogren's syndrome, systemic sclerosis/CREST syndrome, polymyositis/dermatomyositis and mixed connective tissue disease.Cases were female residents of King County, Washington who were diagnosed by a rheumatologist between January 1, 1983 and December 31, 1991 as having a disease of interest. Two control groups were used. The 'new' control group was identified by random digit telephone dialing and was frequency matched to the case group on age at diagnosis and calendar year of diagnosis. Mailed questionnaires were used for concurrent data collection on the cases and on the 'new' control group, with a telephone administered questionnaire for non-respondents. The 'pre-existing' control group had been used for three other epidemiologic studies, and was identified and had in-person interviews before 1992, when mass media attention to the breast implant issue intensified.Of the 532 women identified with a connective tissue disease, 427 (80.3%) returned a questionnaire or completed a telephone interview. The response rate among 'new' controls was 74.3% and 79.0% among the 'pre-existing' controls. Six cases (1.4%) had breast implants prior to their CTD diagnosis: 4/161 (2.5%) of cases with Sjogren's syndrome; 2/191 (1.1%) with systemic lupus erythematosus; 0/55 with progressive systemic sclerosis or CREST syndrome; 0/17 with polymyositis or dermatomyositis; and 0/3 with mixed connective tissue disease. In the 'new' control group 24/1577 (1.5%) women reported having implants prior to their reference date, as did 16/1672 (1.0%) women in the 'pre-existing' control group. Using the 'new' control group, after adjusting for age, calendar year, and race (white, black, other), the odds ratio for any CTD was 0.9 (95% CI: 0.4, 2.3), for systemic lupus erythematosus it was 0.8 (95% CI: 0.2, 3.4), and for Sjogren's syndrome it was 1.6, (95% CI: 0.5, 4.7). Using the 'pre-existing' control group, and with similar adjustment, for any CTD the odds ratio was 1.3 (95% CI: 0.4, 4.1), for systemic lupus erythematosus it was 1.6 (95% CI: 0.3, 7.3), and for Sjogren's syndrome the odds ratio was 1.8 (95% CI: 0.4, 7.8).We found little association between breast implants and the connective tissue diseases studied.