Occupational silica exposure as a risk factor for scleroderma: a meta-analysis

Among potential environmental risk factors for systemic sclerosis (SSc), occupational exposures have received some attention. In this meta-analysis, we examined the association between SSc and occupational exposure to silica. We searched Medline, Toxline, BIOSIS, and Embase (1949 and November 2009) for original articles published in any language. Sixteen studies are included in the analysis, of which, 3 are cohort studies, 9 case-control and 4 are of other designs. The combined estimator of relative risk (CERR) and 95% confidence interval (CI) were calculated using fixed or random effect models. Significant heterogeneity was detected (I (2) = 97.2%; P < 0.01), and the CERR was 3.20 (95% CI, 1.89-5.43). The CERR for studies in females was 1.03 (95% CI, 0.74-1.44) and was 3.02 (95% CI, 1.24-7.35) for males. The CERR for case-control studies was 2.24 (95% CI, 1.65-3.31) and was 15.49 (95% CI, 4.54-52.87) for cohort studies. The findings suggest that silica exposure may be a significant risk factor for developing SSc and specifically in males. Further observational studies examining the role of occupational silica exposure in the context of other risk factors are needed.