Juvenile myasthenia gravis in Norway: A nationwide epidemiological study.

BACKGROUND: The aim of this study was to assess the incidence rate and prevalence of autoimmune myasthenia gravis (MG) among children in Norway. METHODS: This retrospective population-based study was performed in Norway from January 2012 to December 2013. Cases of juvenile MG (JMG) with onset < 18 years were identified through searches in coding systems of electronic patient records at the 15 main hospitals in Norway from 1989 to 2013. In addition, the acetylcholine receptor antibody database at Haukeland University Hospital and the clinical nationwide MG database at Oslo University Hospital were searched for cases of JMG. Diagnosis and age at onset were verified through medical records. Incidence and prevalence rates were calculated using the Norwegian population as reference. RESULTS: In total 63 unique JMG cases were identified. This corresponds to an average annual incidence rate of 1.6 per million. Incidence rate was stable over the study period. Prevalence of JMG was 3.6-13.8 per million. Females constituted the majority of JMG cases (55 vs 8 males). The risk of JMG was higher among females both in the postpubertal and prepubertal group (p < 0.001 and p = 0.02, respectively). CONCLUSION: This study confirms the rarity of JMG in Norway, especially among males, and shows a stable incidence rate over the last 25 years.

An up-date on health-related quality of life in myasthenia gravis -results from population based cohorts.

UNLABELLED: Current available therapies control Myasthenia gravis (MG) reasonably well, but Health Related Quality of life (HRQOL) remains lower than expected. The aim was provide insights in how HRQOL in MG stands across borders and time, compare the scores to general population controls and other chronic disorders and assess the impact of potential predictors for quality of life such as a) clinical characteristics b) antibodies c) thymoma and d) treatment in a population-based cohort. METHODS: We designed a population-based cross-sectional study including 858 patients, 373 from Norway and 485 from the Netherlands. The Short Form Health Survey 36 (SF-36) and a cross-cultural validated questionnaire were used. Data were in addition compared to the general population, other chronic diseases and previous studies. RESULTS: Mean physical composite score was 59.4 and mental composite score 69.0 with no differences between the countries. The mean HRQOL score was lower in patients with bulbar and generalized symptoms (p < 0.001) compared to sex and age adjusted healthy controls, but not in patients with ocular symptoms or patients in remission. Multivariate analysis revealed that female gender, generalized symptoms and use of secondary immunosuppressive drugs at the time of testing were risk factors for reduced HRQOL. CONCLUSIONS: Remission and absence of generalized symptoms were favorable factors for HRQOL in MG patients. Historically, the HRQOL levels have not changed since 2001 and no new clinical predictors could be detected in this exhaustive population-based study. Further studies should explore the impact of non clinical factors like ethnic variations, socio-economic and hormonal factors on HRQOL.

Smoking and socio-economic status may affect myasthenia gravis.

BACKGROUND AND PURPOSE: The influence of environmental factors in myasthenia gravis (MG) is unknown. The aim of this cross-sectional population-based study was to investigate if smoking and socio-economic status (SES) were associated with MG in the Norwegian population. METHODS: Subjects were 491 MG patients identified in Norway at the time of the study (point prevalence 12.7/100 000). A questionnaire covering smoking habits and markers of SES (education and occupation) was mailed to all patients. Population data were obtained from Statistics Norway. RESULTS: A total of 375 (76.6%) patients completed the questionnaire (236 women, mean age 59 ± 18 years), of which 193 reported to be early onset MG (EOMG, onset ≤40 years, 155 women). Compared with the general population, current smoking was more prevalent amongst MG patients [risk ratio (RR) 1.5; 95% confidence interval (CI) 1.1-1.9], most of whom had EOMG. Female MG patients had higher education compared with the general population (RR 4.5; 95% CI 3.2-6.2). Male MG patients were similar to the general population regarding both education and occupation, except for a subset of late onset MG who had shorter education (RR 1.9; 95% CI 1.1-3.2) and had worked in crafts and related trades. About half of working age MG patients received disability pension, a finding significantly related to low educational level and a more severe disease course (P < 0.001). CONCLUSION: This is the first report indicating that smoking and SES may affect MG. Further studies investigating their role as potential risk factors are warranted.

Development and validation of a self-administered questionnaire for myasthenia gravis patients.

BACKGROUND: To date, the investigation of the epidemiological profile of myasthenia gravis (MG) is sparse, and the influence of environmental and lifestyle factors on the occurrence of the disease remains thus unknown. The main aim of this study, which is part of a European collaborative project (EuroMyasthenia), was to develop a self-administered questionnaire to investigate these potential predisposing factors for MG. No instrument for investigating these particular factors has previously been designed for MG patients. MATERIAL AND METHODS: The questionnaire was developed in 3 stages: (1) devising a draft questionnaire based on questions derived from previously validated questionnaires and self-designed questions on MG characteristics; (2) testing the questionnaire on Norwegian MG patients (n = 57), and (3) assessing the content and criterion validity, and test-retest reliability, of the final questionnaire. RESULTS: The questionnaire was easy to use and showed good feasibility for MG patients. Psychometric evaluation established the validity and reliability of the self-designed questions on MG characteristics. CONCLUSION: This is the first validated instrument developed to identify self-assessed environmental factors and potential predisposing factors for MG, and suitable for use in large-scale epidemiological studies.