Cigarette smoking, alcohol consumption, and the risk of systemic lupus erythematosus: a case-control study.

OBJECTIVE: To investigate the effects of cigarette smoking and alcohol consumption on the development of systemic lupus erythematosus (SLE). METHODS: We interviewed 125 patients with SLE and 125 controls in a case-control study. Demographically similar controls randomly selected from outpatient clinics were matched to SLE cases for sex and age. Clinical data, including cigarette smoking, drinking habits, and other demographic variables, were collected by an interview-administered questionnaire. RESULTS: To minimize bias associated with reactive habits induced by disease, cigarette smoking before the diagnosis of SLE was the primary variable for subsequent analysis. Analysis of the data by multivariate conditional logistic regression revealed that both cigarette smoking before SLE diagnosis and ex-smoking before SLE diagnosis significantly increased the risk of development of SLE (OR 6.69, 95% CI 2.59, 17.28, p < 0.001; and OR 3.62, 95% CI 1.22, 10.70, p = 0.02, respectively). This association remained even when statistically controlling for the effects of family history and education, indicating an independent effect. Alcohol did not place an individual at increased risk nor did it have a protective role. CONCLUSION: The results of this study provide further evidence that cigarette smoking may be an associated risk factor for the development of SLE.