Carolina Lupus Study (CLU)
The Carolina Lupus Study is the first population-based epidemiologic study to examine the influence of hormonal and occupational exposures, in addition to genetic factors affecting immune function and metabolism, on systemic lupus erythematosus (SLE). The study included 265 patients with lupus or “cases” and 355 people without lupus or “controls” living in 60 counties in North Carolina and South Carolina. The research team collected information using a structured in-person interview focusing on reproductive and occupational histories. In addition, the collaborators obtained a blood sample from 92% of the cases and 85% of the controls.
Contrary to the their expectations, the team found little evidence that higher estrogen exposures were associated with an increased risk of SLE (Cooper et al., Arthritis Rheum, 2002) . The primary focus of the occupational assessment was on exposure to respirable crystalline silica (quartz), a common mineral found in rocks and soil. The results of the analysis of occupational exposure to silica dust in relation to risk of SLE were striking: a dose-response across levels of exposure, with an approximate two-fold increased risk in the medium exposure category and a four-fold increased risk in the high exposure category. As expected, the prevalence of high exposure was lower among women compared with men, but the associations were seen in both groups (Parks et al., Arthritis Rheum, 2002) . Results for other occupational exposures were published (Cooper et al., J Rheum, 2004) .
SLE is a severe, disabling, autoimmune disease that can lead to significant morbidity and mortality, particularly from renal and cardiovascular disease. African-Americans are two to three times more likely than Caucasians to develop the disease but the reasons for this increased disease risk are unknown. Like several other autoimmune diseases, the vast majority, approximately 85%, of SLE patients are female. Genetic susceptibility plays an important role in SLE and other autoimmune diseases. Other factors must also be involved, but little is known about the contribution of environmental or other non-genetic stimuli to disease initiation and progression. The Carolina Lupus Study will address these stimuli.