Overweight MG patients at greater risk of disease worsening: Study
Higher BMI linked to increased risk of progression to generalized MG
A higher body mass index (BMI), a measure of body fat based on height and weight, is associated with an increased risk of progression from ocular to generalized myasthenia gravis (MG), according to a study in China.
Ocular MG is a type of MG in which muscle weakness is restricted to the muscles that control eye and eyelid movements, while generalized MG (gMG) also affects other muscle groups.
“Preventing the progression from [ocular to generalized MG] is crucial for disease outcomes. Our findings suggest that weight loss might benefit MG patients,” researchers wrote.
The study, “Impact of body mass index on clinical presentation and prognosis in myasthenia gravis,” was published in the Orphanet Journal of Rare Diseases.
MG is caused by self-reactive antibodies targeting proteins involved in nerve-muscle communication, most commonly acetylcholine receptors (AChRs), leading to muscle weakness and fatigue. Many patients start experiencing eye-related symptoms that later progress to affect other muscles.
Higher BMI linked to onset, severity of several autoimmune conditions
Obesity has been associated with a chronic inflammatory state potentially leading to immune diseases. A higher BMI has also been linked to the onset and severity of several autoimmune conditions.
“However, the relationship between BMI and MG appears inconsistent,” the researchers wrote.
To learn more about the effects of BMI on the clinical presentation and prognosis of MG, researchers conducted a large-scale observational study enrolling 940 adults who had been diagnosed with the disease at three hospitals in China.
Participants were a median age of 50 years, most were women (54.3%), and they had been living with MG for a median of 8.6 months.
They were divided into two groups, depending on their BMI: 524 were placed in a low BMI group (BMI below 24 kg/m2); and 416 were placed in a high BMI group (24 kg/m2 or higher).
Those included in the high BMI group were significantly older (55 vs. 44 years), were less commonly women (41.8% vs. 64.1%), and had a shorter disease duration (6.4 vs. 10.7 months). They also more commonly had ocular MG (47.4% vs. 37%), eye symptoms at disease onset (71.9% vs. 60.3%), and anti-AChR antibodies (83.2% vs. 75.1%).
Conversely, they less frequently underwent thymectomy, or surgery to remove the thymus gland (25.3% vs. 33.1%).
A total of 734 participants were regularly monitored every three to six months. During a median of 33 months (nearly three years) of follow-up, a higher proportion of patients in the low BMI group were treated with immunotherapy (78.6% vs. 70.8%).
Higher BMI associated with greater risk of disease generalization
A higher BMI was associated with a greater risk of disease generalization — a 6% higher risk with each additional 1 kg/m² — but not with the probability of achieving a response on the MG Activities of Daily Living (MG-ADL), which is a scale that assesses the impact of MG on daily life.
BMI was also not linked to the likelihood of achieving minimal symptom expression (MSE) — a disease state where patients have minimal or no noticeable MG symptoms (MG-ADL score of 0 or 1).
“In our cohort, fewer high BMI patients received immunotherapy during follow-up, which could influence the generalization of [ocular MG],” the researchers wrote. However, the effect persisted, even after adjusting data for immunotherapy and other confounding factors.
“This study has demonstrated the impact of BMI on the clinical presentation and prognosis of MG. We found that a high baseline BMI was associated with an increased risk of [ocular] MG generalization, although it was not linked to the risk of ADL response or MSE,” the researchers wrote.
“Future studies are needed to explore the impact of BMI changes on MG prognosis and their causal relationship,” they added.
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