Abstract
Objective This study investigated the association between smoking and myasthenia gravis (MG), a chronic autoimmune disorder that affects neuromuscular junctions. Methods Data were collected from the Japan MG Registry 2021 survey conducted between April and October 2021. MG severity was assessed using the MG activities of daily living score and MG Foundation of America (MGFA) classification. The Brinkman Index, calculated as the number of cigarettes smoked per day multiplied by the number of years smoked, was used to evaluate the correlation between smoking exposure and MG severity. We also compared the smoking rates of individuals with and without MG stratified by age and sex. Results Of the 1,402 patients selected from the Japanese registry, higher smoking rates were observed in patients with MG than in the general population. Compared with never-smokers, women with MG who smoked were younger and had a higher prevalence of ocular symptoms. A weak correlation was observed between MGFA and Brinkman indices among men with MG who smoked. No correlation was observed between smoking status and MG severity in women who smoked. Conclusion This study utilized one of the largest datasets on MG and smoking; thus, it provides valuable insights into the association between smoking and MG.