Smoking may be an independent risk factor for earlier onset of anti-acetylcholine receptor (anti-AChR) antibody-positive myasthenia gravis (MG), according to a study published in Immunological Medicine.

During the study, patients who were smokers at the time of MG diagnosis were significantly younger than patients who were former smokers (P <.001) or never smokers (P <.01). In a subset analysis, current smokers or patients who had quit 10 years or less prior to MG development were significantly younger (P <.0001) at the time of diagnosis than those who were former smokers who had quit more than 10 years prior to the development of MG.

In a linear regression model adjusted for sex and the presence of thymoma, concurrent smoking was significantly associated with younger age at onset of MG.

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“Our results suggest that smoking is an independent risk factor for the earlier development of anti-acetylcholine receptor antibody-positive MG and further support the putative link between smoking and MG,” the authors said.

In subsets broken up according to sex, women who were smokers were significantly younger (P <.01) than never-smokers, and men who were smokers were significantly younger (P <.01) than former smokers. Among former smokers, women were significantly younger than men at the onset of MG (P <.05).

The trend of concurrent smokers and former smokers who quit 10 years or less before MG onset being younger than those who quit more than 10 years prior continued within the sex subgroups for both men (P <.01) and women (P <.001).

Concurrent smokers were also significantly younger than never smokers among the subset of patients with thymoma (P <.05) and were significantly younger than former smokers among patients without thymoma (P <.01). No significant difference in age was observed between former smokers with thymoma and those without, however.

A younger age at onset was again observed for concurrent smokers and those who quit 10 years or less before diagnosis, and those who quit more than 10 years prior to diagnosis. The trend was also reported for both patients who had thymoma (P <.001) and those without thymoma (P <.01).

A total of 138 patients with MG aged 16 years or older were analyzed in the study. The patients were divided into former smokers (n=42), never smokers (n=62), and concurrent smokers (n=34).

Reference

Miyazaki Y, Sakushima K, Niino M, et al. Smoking and younger age at onset in anti-acetylcholine receptor antibody-positive myasthenia gravis. Immunol Med. Published online November 8, 2022. doi:10.1080/25785826.2022.2143077