Silvia Falso1, Pietro Zara2, Sofia Marini1, Mariangela Puci3, Eleonora Sabatelli4, Giovanni Sotgiu2, Martina Marini1, Gregorio Spagni5, Amelia Evoli1, Paolo Solla6, Raffaele Iorio4, Elia Sechi2
1Università Cattolica del Sacro Cuore, 2University of Sassari, 3University Hospital of Sassari, 4IRCCS Fondazione Policlinico Agostino Gemelli, 5German Center for Neurodegenerative Diseases (DZNE) Berlin, 6Ospedale Binaghi
Objective:
To investigate the association between seasonality and onset of myasthenia gravis (MG) symptoms.
Background:
Environmental factors may contribute to MG development, sometimes with seasonal patterns of exposure. However, whether seasonality has an impact on MG incidence remains unclear.
Design/Methods:
We retrospectively reviewed data of MG patients with acetylcholine receptor (AChR)-IgG and disease onset between January 2010-December 2019, from two Italian cohorts: 1) An hospital-based cohort of patients consecutively seen at the Neurology Unit of the IRCCS Fondazione Policlinico Gemelli, in Rome; and 2) a previously described population-based cohort of incident cases resident in the Sanitary District of Sassari, in the region of Sardinia. MG cases were assigned to four season-trimesters (e.g., summer trimester = June-August) based on month of MG symptoms onset, seasonal variability was explored comparing the median number of incident MG cases per trimester over the study period (Kruskal Wallis). Generalized additive model (GAM) was also applied to evaluate the relationship between temperature and new MG cases.
Results:
A total of 316 patients were included: hospital-based cohort, 214; population-based cohort, 102. Median age at onset was 66 years (range, 8-92); 41% were female. The seasonal MG incidence was significantly higher in summer with 11 cases (range, 7-15), compared to 6 (3-11) cases in autumn, 8.5 (3-11) cases in winter, and 7 (2-10) cases in spring; p=0.009. We also found a significant, non-linear association between average temperature and MG cases; p=0.005.
Conclusions:
Our study suggests that onset of AChR-MG may follow a clear seasonal distribution, with a peak during the summer months. Seasonal variability at MG onset was comparable in patients from two geographically and genetically distinct Italian regions, making unlikely a random association and suggesting a major role of environmental factors in unmasking MG symptoms.
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