Birnbaum S1,2,3, Sharshar T4,5,6, Bachasson D3, Hogrel J-Y3, Portero P2
1Assistance Publique des Hôpitaux de Paris, Unité de Recherche Clinique Paris Île- de- France Ouest (URC PIFO), Raymond Poincaré Hospital, Garches, France, 2Université Paris-Est Créteil, Bioingénierie, Tissus et Neuroplasticité, EA 7377, Creteil, France, 3Institute of Myology, Neuromuscular Physiology Laboratory, Paris, France, 4Hospital Sainte Anne, Medical and Surgical Neurointensive Care Centre, Paris, France, 5Institute Pasteur, Laboratory of Human Histopathology and Animal Models, Paris, France, 6Université Paris Descartes, Paris, France
Background: Muscle weakness and fatigability, the primary symptoms in auto-immune MG, negatively impact daily function and quality of life (QOL). To what extent symptoms limit physical activity is unknown. To date, information about physical activity (PA) patterns and sedentary behaviour (SB) in subjects with auto-immune myasthenia gravis (MG) is lacking.
Purpose: This study aimed to describe habitual activity of female adults with MG and explore associations between PA patterns, SB, clinical characteristics and QOL. It was hypothesised that reduced QOL would be related to reduced PA levels as has been found in the general population.
Methods: Cross-sectional study design. Subjects with confirmed MG and control subjects wore a tri-axial accelerometer (DynaPort Movemonitor, McRoberts) on their lumbar spine for 7 consecutive days. Daytime recordings (between 7am-11pm) ≥ 4 days with ≥ 12 hours wear-time were considered for analysis. SB was defined as activity below 1.5 metabolic equivalents (METS). Moderate-intensity PA was defined as 3-6 METs, vigorous as 6-9 METs and very vigorous as > 9 METs. Data was analysed relative to worn time. Unpaired Mann-Whitney tests were used to study between-group differences. Spearman's correlation was used to investigate relationships between variables for MG subjects (age, BMI, disease severity and duration, 6MWD and QOL).
Results: Thirty-four females with mild or moderately-severe MG were included. Six minute walking distance (6MWD) was reduced (86±13% of predicted values) as was self-perceived QOL for both MG-specific QOL and the WHO-QOL Bref (physical domain) scores. MG subjects were compared to 113 age and weight-matched female control subjects. BMI was greater for MG subjects (p = 0.01). SB was greater in individuals with MG (p = 0.04) however time spent doing vigorous and very-vigorous intensity PA was greater in control subjects (p 0.01). The amount of moderate-intensity PA was similar between MG and controls (p = 0.14). However, subjects with MG underwent significantly less periods of bouted moderate-intensity PA (p 0.01). Mean daily step count was also lower in MG (p 0.01).
For MG subjects SB was positively correlated with BMI (p = 0.03, rho = 0.38). Vigorous-intensity PA positively correlated with 6MWD, (p 0.01, rho = 0.46), and negatively with BMI (p = 0.01, rho = -0.42). QOL (MG-QOL-15-F) positively correlated with very vigorous-intensity PA (p = 0.01, rho = 0.43). Self-perceived walking difficulty (item 12, MGQOL-15-F) correlated with 6MWD (p = 0.02, rho = -0.41) and BMI (p = 0.02, rho = 0.39) and BMI negatively correlated with 6MWD (p 0.01, rho = -0.45).
Conclusion(s): Whilst subjects with MG are more sedentary than healthy controls, they are not inactive. They do as much moderate-intensity PA (per day), however individuals with MG fragment this activity into shorter bouts throughout the day.
Implications: Further research is needed to understand the causes of reduced QOL in MG. Whilst higher-intensity PA is related to higher QOL and greater walking performance it may not be possible for all individuals with MG. These results should be taken into consideration in the design of future exercise programs for MG.
Keywords: auto-immune myasthenia gravis, physical activity, quality of life
Funding acknowledgements: PHRC grant - French Ministry of Health (AOR12149), sponsor AP-HP, conducted in collaboration with the Institute of Myology
Purpose: This study aimed to describe habitual activity of female adults with MG and explore associations between PA patterns, SB, clinical characteristics and QOL. It was hypothesised that reduced QOL would be related to reduced PA levels as has been found in the general population.
Methods: Cross-sectional study design. Subjects with confirmed MG and control subjects wore a tri-axial accelerometer (DynaPort Movemonitor, McRoberts) on their lumbar spine for 7 consecutive days. Daytime recordings (between 7am-11pm) ≥ 4 days with ≥ 12 hours wear-time were considered for analysis. SB was defined as activity below 1.5 metabolic equivalents (METS). Moderate-intensity PA was defined as 3-6 METs, vigorous as 6-9 METs and very vigorous as > 9 METs. Data was analysed relative to worn time. Unpaired Mann-Whitney tests were used to study between-group differences. Spearman's correlation was used to investigate relationships between variables for MG subjects (age, BMI, disease severity and duration, 6MWD and QOL).
Results: Thirty-four females with mild or moderately-severe MG were included. Six minute walking distance (6MWD) was reduced (86±13% of predicted values) as was self-perceived QOL for both MG-specific QOL and the WHO-QOL Bref (physical domain) scores. MG subjects were compared to 113 age and weight-matched female control subjects. BMI was greater for MG subjects (p = 0.01). SB was greater in individuals with MG (p = 0.04) however time spent doing vigorous and very-vigorous intensity PA was greater in control subjects (p 0.01). The amount of moderate-intensity PA was similar between MG and controls (p = 0.14). However, subjects with MG underwent significantly less periods of bouted moderate-intensity PA (p 0.01). Mean daily step count was also lower in MG (p 0.01).
For MG subjects SB was positively correlated with BMI (p = 0.03, rho = 0.38). Vigorous-intensity PA positively correlated with 6MWD, (p 0.01, rho = 0.46), and negatively with BMI (p = 0.01, rho = -0.42). QOL (MG-QOL-15-F) positively correlated with very vigorous-intensity PA (p = 0.01, rho = 0.43). Self-perceived walking difficulty (item 12, MGQOL-15-F) correlated with 6MWD (p = 0.02, rho = -0.41) and BMI (p = 0.02, rho = 0.39) and BMI negatively correlated with 6MWD (p 0.01, rho = -0.45).
Conclusion(s): Whilst subjects with MG are more sedentary than healthy controls, they are not inactive. They do as much moderate-intensity PA (per day), however individuals with MG fragment this activity into shorter bouts throughout the day.
Implications: Further research is needed to understand the causes of reduced QOL in MG. Whilst higher-intensity PA is related to higher QOL and greater walking performance it may not be possible for all individuals with MG. These results should be taken into consideration in the design of future exercise programs for MG.
Keywords: auto-immune myasthenia gravis, physical activity, quality of life
Funding acknowledgements: PHRC grant - French Ministry of Health (AOR12149), sponsor AP-HP, conducted in collaboration with the Institute of Myology
Topic: Neurology; Health promotion & wellbeing/healthy ageing
Ethics approval required: Yes
Institution: ANSM
Ethics committee: CPP Île-de-France XI
Ethics number: 13064 for the MGEX trial
All authors, affiliations and abstracts have been published as submitted.
