Occupational and environmental risk factors for idiopathic pulmonary fibrosis: A multicenter case-control study

Occupational exposures were investigated in a multicenter case-control stud y of clinically and histologically diagnosed idiopathic pulmonary fibrosis (IPF), a chronic diffuse interstitial lung disease of unknown etiology. Res ults are based on 248 cases, aged 20-75 years, diagnosed at 16 referral cen ters between January 1989 and July 1993. There were 491 controls ascertaine d by random digit dialing and matched to cases on sex, age, and geographic region. Data were collected using a standard telephone questionnaire. Occup ational factors were based on a detailed history of jobs lasting 6 months o r more and job activity, hobby, and specific substance checklists. Several occupational factors, adjusted for age and smoking in conditional multivari ate logistic regression analyses, were significantly associated with IPF: f arming (odds ratio (OR) = 1.6, 95% confidence interval (CI): 1.0, 2.5); liv estock (OR = 2.7, 95% CI: 1.3, 5.5); hairdressing (OR = 4.4, 95% CI: 1.2, 1 6.3), metal dust (OR = 2.0, 95% CI: 1.0, 4.0); raising birds (OR = 4.7, 95% CI: 1.6, 14.1); stone cutting/polishing (OR = 3.9, 95% CI: 1.2, 12.7); and vegetable dust/animal dust (OR = 4.7, 95% CI: 2.1, 10.4). Interaction was detected between smoking and exposure to livestock (p = 0.06) and farming ( p = 0.08). Results confirm previous studies showing increased risk associat ed with dusty environments.