Association between environmental factors and onset of psoriatic arthritis in patients with psoriasis
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OBJECTIVE: To investigate the association between potential environmental exposures and the development of psoriatic arthritis (PsA) in patients with psoriasis. METHODS: In this case-control study, the cases were patients with recent-onset PsA. The controls were psoriasis patients without arthritis. The occurrence of the following environmental exposures was recorded through a standardized questionnaire: smoking, alcohol consumption, infections, injuries, physically demanding occupational tasks, stressful life events, vaccinations, and female hormonal exposures. The association between each exposure to environmental events and disease status was assessed through logistic regression after adjustment for age, sex, education level, and duration and severity of psoriasis. RESULTS: There were 159 subjects in each group. The following exposures remained significantly associated with PsA following multivariate logistic regression: lifting cumulative loads of at least 100 pounds/hour (odds ratio [OR] 2.8, 95% confidence interval [95% CI] 1.51-5.05), infections that required antibiotics (OR 1.7, 95% CI 1.00-2.77), smoking (OR 0.6, 95% CI 0.36-0.89), and injuries (OR 2.1, 95% CI 1.11-4.01). The results were not appreciably changed with the inclusion of each of these factors in a single regression model; however, the level of significance for injuries had become borderline. No association was found between PsA and alcohol consumption, vaccination, stressful life events, and female hormonal exposures. CONCLUSION: Lifting heavy loads and infections that required antibiotics were associated with the occurrence of arthritis among patients with psoriasis. There was an inverse association between smoking and PsA. Further studies are necessary to determine whether these and other environmental factors are moderated by predisposing genetic factors.
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