Surgery, westernized dietary habits and other risk factors for mixed connective tissue disease in a Japanese population: Comparison with systemic lupus erythematosus and systemic sclerosis

Objective: The etiology of mixed connective tissue disease (MCTD) has not been elucidated in detail. The aim of the present study was to evaluate the risk factors for MCTD in comparison with systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) in a Japanese population. Subjects and Methods: A total of 28 MCTD, 57 SLE, and 42 SSc patients, and 144 healthy volunteers were asked to answer a self-administered questionnaire. Case-control studies were performed for the risk factors of these three diseases. Results: Compared with the controls, a medical history of connective tissue diseases as well as a medical history of surgery were seen more commonly among MCTD, SLE and SSc patients, whereas a medical history of cancer was observed more commonly among SSc patients than the controls. Even after controlling for age and sex, a medical history of surgery increased the risk of MCTD as well as SLE. On the other hand, westernized dietary habits showed an increased risk for MCTD, SLE and SSc after adjusting for age and sex. Conclusion: The present study suggests some factors related to the development of MCTD, SLE or SSc in the Japanese population. However, further studies are needed to confirm the findings of the present study because of the small number of cases involved.