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

Abstract

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.

Fig. 1

Overview over study procedure. The study was conducted among all MG patients in Norway and the contiguous regions of South- and North Holland in the Netherlands, including an additional MuSK Sample from entire Netherlands. The case identification and inclusion criteria were the same in both countries. The case search in the Norwegian study area was performed nationwide including 4 university clinics, 15 local clinics and 11 private clinics. Recruitment started: 01.01.2008. Recruitment stopped: 01.11.2009. The case search in the Dutch study was conducted in two regions and the affiliation to the geographical area was defined by postal code. The area had 4 university clinics, 25 local clinics and one private clinic. Recruitment started: 01.10.2011. Recruitment stopped: 01.01.2012. 43 patients were not eligible for questionnaire study because of change of address, dementia and other co-morbidities and delay in registration of ICD-code. Abbreviations: ICD = international classification diagnosis. F: M = female: male ratio

Fig. 2

HRQOL in Myasthenia Gravis compared with healthy controls. The figure illustrates the population based MG cohorts in Netherlands (a) and the Norway (b) compared with healthy controls from their own countries. Healthy control data is provided by Loge et al.; Norway [24] and Aaronesen et al. [22]. In summary, MG patients scored lower than healthy controls and females scored lower than males and those in remission similar to healthy controls. The Score range from 0-100. Higher score indicate better Health related quality of life (HRQOL). Solid line is score of reference population for men, and dotted line is score of reference population for women in their respective countries. Horizontal axes show the 8 domains of SF-36 and composite scores

Fig. 3

HRQOL by phenotype and antibodies. a MG patients in remission and absence of generalized symptoms scored significantly better than the other groups on both composite scores (p < 0.001). b Antibody profile did not affect HRQOL outcomes

Fig. 4

HRQOL in early MG patients compared to other chronic diseases. Early Norwegian Myasthenia Gravis patients from 0-3 years after onset scored similar to MS patients [25], but better than Parkinson’s patients [26] and Rheumatoid Arthritis patients with a similar disease duration [37]

Fig. 5

Overview over HRQOL measured by SF-36 from 2001-2012. Studies providing norm-based scoring are shown. Bars illustrate the distribution of MGFA score within the cohorts, lines illustrate the PCS and MCS. Vertical axis shows SF-36 score 0-100 for lines and distribution of MGFA class within the cohort. Padua et al. reported lower scores in 2002 than we did (p < 0.001), however the cohort consisted of fewer patients in remission (7 %) and 89 % in MGFA class II-IV [1]. Paul et al. 2001 [2], provided not norm-based scoring, but PCS 57.6 (27) and 65.5 (24.8) were not significant different from our study