Scleroderma and occupational exposure to hand-transmitted vibration

Objectives: To determine whether occupational exposure to hand-transmitted vibration is a risk factor for scleroderma (systemic sclerosis, SSc), two c ase-control studies were conducted in the provinces of Trento and Verona, n ortheastern Italy. Methods: In the Trento study, 21 patients with a diagnos is of either systemic or localised scleroderma were recruited from those ad mitted to all hospitals of the province from I January 1976 to 31 December 1991. For each case, two age- and gender-matched controls were selected. In the Verona study, cases included 55 patients diagnosed with SSc and clinic ally followed at the rheumatology clinic of the local university hospital b etween I January 1997 and 30 June 1999. The controls included 171 subjects frequency-matched by gender and age group. In both studies, all subjects we re interviewed by structured questionnaire containing items on personal cha racteristics, smoking and drinking habits, use of medicines, occupational h istory and complete medical history. Women were also investigated about sil icone implants and cosmetic surgery. Jobs and job tasks involving the use o f vibratory tools, with or without concomitant exposure to silica dust in m ining and non-mining occupations, were carefully investigated. A minimum cr iterion of 6 months was required for exposure duration. Results: In the Tre nto Study, men with scleroderma were more likely than controls to have had exposure to hand-transmitted vibration (odds ratio (OR) 1.5, 95% confidence interval (95% CI) 0.1-74.1) or silica dust (OR 5.2, 95% CI 0.5-74.1), but the association was not significant. The scleroderma patients were miners o r stone workers who had operated jackhammers and rock drills. In the Verona study, a greater, although not statistically significant, odds of SSc was observed in men exposed to hand-transmitted vibration (OR 2.4, 95% CI 0.4-1 4.0) and in women exposed to silica (OR 2.4, 95% CI 0.4-15.5). The SSc pati ents with vibration exposure were machinery operators or metal workers who had used grinders and impact wrenches. Conclusions: Our case-control studie s did not show a significant association between scleroderma and hand-trans mitted vibration, with or without concomitant exposure to silica dust. Owin g to the rarity of the disease and the small number of cases in the present studies, a genetic susceptibility to connective tissue disorders in SSc pa tients with occupational exposure to hand-transmitted vibration and/or sili ca cannot be ruled out.