Association of smoking with thyroid eye disease and related diplopia in a Japanese population: a retrospective study.

PURPOSE: To investigate the association between current smoking and thyroid eye disease (TED), and diplopia among TED patients. STUDY DESIGN: Retrospective case-control study. METHODS: This study included 12,038 individuals (10,269 with TED and 1769 controls) from a single ophthalmology center in Japan. Smoking status, demographic characteristics, and clinical features were obtained from medical records. Multivariable logistic regression was performed to evaluate the associations between current smoking and (1) TED diagnosis and (2) diplopia among TED patients, adjusting for age, sex, TSAb levels, and family history of thyroid disease, with stratified analyses by age and sex. RESULTS: Current smoking was significantly associated with TED (adjusted odds ratio [aOR] = 1.41; 95% CI 1.24-1.61; p < 0.01), with significant effects observed in both sexes and a stronger association in males (aOR = 1.61) than in females (aOR = 1.36). Among TED patients, current smoking was also associated with diplopia (aOR = 1.45; 95% CI 1.29-1.62; p < 0.01), significantly in females (aOR = 1.57; p < 0.01) but not in males (aOR = 1.20; p = 0.09). The association with diplopia was not statistically significant in patients aged 60 years and older. CONCLUSIONS: Current smoking is significantly associated with both the development and severity of TED, including diplopia, in a Japanese population. These findings support the integration of smoking cessation counseling with the routine management of patients with thyroid disease.