Statin treatment may increase risk of MG onset, worsening: Study
Risk increased in months after initiation, but not later on
Patients should be monitored for symptoms of myasthenia gravis (MG) for approximately six months after starting treatment with statins, common blood cholesterol-lowering medications, according to a study.
Hong Kong-based researchers found a significantly increased risk for MG onset and exacerbation, or worsening, in the first seven months after starting treatments with statins, but not for the subsequent 18 months. The risk of developing MG was most notable in statin users who were older than 60.
“To our knowledge, our population-based study is the first to provide evidence of an increased risk of MG onset in the first months and subsequent six months following statin initiation,” the researchers wrote. The study, “Myasthenia gravis following statin therapy: evidence from target trial emulation and self-controlled case series study,” was published in Nature communications.
MG is a rare, neuromuscular disorder that leads to weakness and fatigue in muscles used in voluntary movements. Several international organizations, including one in Hong Kong, recently issued a warning about the increased risk of developing or worsening MG following statin therapy. However, few studies have quantitatively investigated the link between MG and statins.
“Given the widespread use of statins worldwide, it is important to analyse the potential association between statins and MG to ensure patient safety,” the researchers wrote.
Real-world data
The researchers used real-world data from electronic health records of over 369,000 people without pre-existing MG, as well as 112 people with pre-existing MG who started taking statins.
In the first month after starting treatment with statins, the incidence rate for MG onset was 51.91 per 100,000 person-years. In contrast, the incidence rate of MG onset in people who did not begin treatment with statins was less than 10 per 100,000 person-years. Person-years is a composite measure that takes into account the number of people participating in a study and the amount of time they were followed. For example, 100,000 person-years may refer to data gathered from 100,000 people who were followed for one year.
The results indicated that people who started taking statins were more than six times more likely to develop MG in the first month following treatment initiation as those who didn’t start taking the cholesterol-lowering medicines.
Risk was still elevated up to seven months after starting statin therapy. The incidence rate of MG onset was 16.27 per 100,000 person-years in the second through to the fourth month after beginning statin therapy, corresponding to a nearly twofold increased risk of MG development. By the fifth through to the seventh month, the incidence rate of MG onset was 15.27 per 100,000 person-years, corresponding to a 1.80 times increased risk.
Statin therapy did not increase the risk of developing MG in the subsequent 18 months.
The researchers noted that despite detecting an increase in the risk of developing MG following statin initiation, the overall risk remained relatively low. “While our study highlighted the increased relative risk of newly diagnosed MG following statin initiation, it also provided reassurance for the physician and patients regarding its overall low risk,” they wrote.
Risk rises with age
The researchers found that people who were older than 60 had a greater risk of developing MG in the first seven months after starting statins than people who were 60 or younger.
“The higher risk of MG onset in individuals aged over 60 years, may be attributed to their medical complexity and reduced tolerance to medications, or the underlying neuromuscular diseases, which emphasizes the need for enhanced attention towards this age group in monitoring for MG symptoms and conducting further diagnostic evaluations when they experience muscle symptoms after taking statins,” the team wrote.
Among the 112 people who had already been diagnosed MG, the incidence rate of exacerbation, or symptom worsening, was also higher than expected in the first seven months after starting statin therapy.
The incidence rate of MG exacerbation was 89.29 per 100,000 person-years in the first month following statin initiation, corresponding to a 10.69-times higher risk of exacerbation.
The incidence rates were 13.38 per 100,000 person-years in the second through to the fourth month after beginning statin therapy, corresponding to a 1.50 times higher risk, and 24.48 per 100,000 person-years in the fifth through the seventh month, corresponding to a nearly threefold higher risk of exacerbation.
Statin therapy did not increase the risk of exacerbation in MG patients in the subsequent 18 months.
“The current findings regarding the consistent trend of increased risk in the subsequent six months remain supportive of the primary conclusion regarding the monitoring for MG symptoms following statin therapy,” the researchers wrote. “Nevertheless, the benefits of the statin far outweigh the risk of this rare adverse event, and our study could also provide reassurance to patients regarding its overall low risk,” they wrote.
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