SYSTEMIC LUPUS ERYTHEMATOSUS: A CASE‐CONTROL EPIDEMIOLOGIC STUDY IN JAPAN

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Abstract
Background. Systemic lupus erythematosus (SLE) is designated by the Japanese government as one of the intractable diseases and all patients, who suffer from these diseases, are registered to get financial aid for treatment. Using newly registered SLE patients, a case‐control study was conducted to evaluate potential risk factors. Methods. Two‐hundred and eighty‐two women SLE patients, newly registered to receive financial aid for treatment, and 292 randomly selected health examination participants at public health centers (controls) were surveyed from April 1988 through March 1990. By means of a self‐administered questionnaire, data concerning demographic variables, smoking and drinking habits, past medical and reproductive history, and family history were collected. Results. Based on unconditional logistic regression analysis, the risk of SLE was significantly increased for current smokers (age‐adjusted odds ratio (OR) = 2.31, 95% confidence interval (CI) (1.34–3.97). Alcohol and milk intake were inversely associated with risk. Family histories of asthma and collagen diseases, including SLE, were associated with significantly elevated risk of SLE (OR = 2.07, 95% ci 1.14–3.77; OR = 5.20, 95% CI 1.08–24.95, respectively). Regarding reproductive function, women with menarche at age 15 or later had significantly higher risk than those, who started menstruating before age 12 (OR = 3.82, 95% CI 1.66–8.81 for menarche at > 15 years and OR = 2.90, 95% a 1.14–7.39 for menarche at 16y). Conclusions. Our study suggests several risk factors, including smoking, family history, and reproductive history that may increase the risk of SLE.