Nearly 60% higher risk of MS seen for people with diabetes in new study

People with diabetes are significantly more likely — with nearly 60% higher odds — to develop multiple sclerosis (MS) than those without the metabolic disease, which is marked by high blood sugar levels, according to a new systematic review and meta-analysis.

A significant association was also observed specifically between type 2 diabetes, the most common form of the condition, and MS risk.

The analysis did not, however, find clear evidence that MS increases the likelihood of developing diabetes.

“Current evidence indicates that [diabetes mellitus], specifically [type 2 diabetes], increases the risk of developing MS,” the researchers wrote. “However, a reverse association remains unconfirmed.”

The study, “Diabetes mellitus and risk of multiple sclerosis: a systematic review and meta-analysis,” was published in the journal Frontiers in Endocrinology.

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MS occurs when the immune system mistakenly attacks the myelin sheath, a fatty coating around nerve fibers that help ensure efficient transmission of nerve signals. This causes inflammation and damage to nerve cells in the brain and spinal cord, leading to a wide range of MS symptoms.

While the exact causes of the disease remain largely unknown, several factors are believed to influence a person’s likelihood of developing the disease.

One such factor is diabetes, a group of chronic conditions characterized by persistently high glucose, or blood sugar, levels.

Seeking evidence of a potential link between diabetes and MS

In type 1 diabetes, the immune system mistakenly attacks insulin-producing cells in the pancreas, leading to a lack of insulin, the hormone that helps move sugar from the bloodstream into cells so it can be used for energy. Type 2 diabetes occurs mainly when the body becomes resistant to insulin or when the pancreas cannot produce enough insulin.

Previous research has suggested a possible link between diabetes and MS. Some studies have reported that diabetes occurs more frequently in people with MS than in those without the neurological disease. Other studies have suggested that people with diabetes may have a higher risk of developing MS.

“However, the nature of their connection and the bidirectional relationship between these diseases remain insufficiently clarified,” the researchers wrote.

To address this knowledge gap, researchers in China analyzed previously published studies investigating the relationship between MS and diabetes. The analysis covered seven studies published between 2010 and 2024, involving more than 3.1 million people.

When the researchers pooled data from two studies examining diabetes as a risk factor for MS, they found that people with diabetes had a 59% higher risk of MS compared with those without the condition. Excluding data from people with type 1 diabetes, the results similarly showed that people with type 2 diabetes had a 46% higher risk of developing MS.

In contrast, an analysis based on data from five studies found no significant increase in the risk of developing type 2 diabetes among people already diagnosed with MS.

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Biology may explain link between conditions

The researchers said several biological mechanisms could help explain why diabetes may increase the risk of MS.

Types 2 diabetes is associated with chronic inflammation and immune system dysregulation, which may affect the brain and spinal cord. Persistently high blood sugar levels can also trigger metabolic changes that may damage cells responsible for producing and repairing myelin.

In contrast, type 1 diabetes and MS are both autoimmune conditions, suggesting they may share some biological pathways that could partly explain why the diseases sometimes occur in the same individuals.

“In conclusion, current evidence suggests that [type 2 diabetes] is associated with an increased risk of developing MS, while a significant association between MS and an elevated risk of [type 2 diabetes] was not confirmed,” the researchers wrote.

Although our meta-analysis indicates an association, this does not establish causality.

The team emphasized, however, that these findings show an association but do not prove a direct cause-and-effect relationship.

“Although our meta-analysis indicates an association, this does not establish causality,” the team wrote.

Still, “clinicians should maintain heightened vigilance for MS” in people with type 2 diabetes, particularly those presenting with neurological symptoms,” the researchers wrote. “Conversely, regular blood glucose monitoring is advisable for MS patients to enable early detection and management of potential [diabetes].”

Because the analysis included a relatively small number of studies and different study designs, the researchers said larger, long-term prospective studies will be needed “to further clarify the nature of the association between [diabetes] and MS.”