Environmental Factors of Importance in Myasthenia Gravis : Emphasis on Physical Activity

Abstract: Myasthenia Gravis (MG) is an autoimmune disease caused by antibodies directed against proteins at the neuromuscular junction (NMJ). The disturbed neuromuscular transmission induces fatigable weakness in skeletal muscles. The severity of MG ranges from purely ocular symptoms to extensive weakness with, at worst, respiratory failure and need of intensive care. Due to different pathogenic antibodies, as well as varying phenotypes there is a classification into MG subgroups.As lifestyle disorders are common conditions they occur also in MG patients. It is unknown whether there are any lifestyle factors associated with MG or MG subgroups. However, medication side effects and disability due to disease could contribute to higher risks for lifestyle related diseases. General treatment guidelines are not suitable to MG patients, since various medications are known to affect the disease negatively and as the tolerance and effects of physical activity in MG is unknown.In this thesis the occurrence of lifestyle related environmental factors in MG patients were investigated. MG epidemiology, subgroup differences and the presence of lifestyle related risks in MG patients were evaluated in Jönköping county in Southern Sweden. The findings were compared to a similar evaluation in a region of Estonia. We found that MG patients in the late-onset disease subgroup had a more disadvantageous pattern of life-style related risk factors, with a higher rate of obesity, smoking and physical inactivity and a lower rate of fish consumption in comparison to matched population controls. Furthermore, we found that despite comparable clinical muscle fatigue status, Estonian MG patients subjectively scored fatigue and disease severity higher than Swedish MG patients. More Estonian patients were physically inactive. The tolerance and effects of physical exercise was further evaluated in two intervention studies, where MG patients with stable disease performed a 12-week-training-program according to general exercise recommendations to healthy adults. We found that physical exercise was well tolerated by the MG patients and that they had a beneficial skeletal muscle response to physical exercise.