Study links NMOSD to increased type 2 diabetes risk

Risk is higher in those on steroid treatment, data show

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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The risk of developing type 2 diabetes is more than 50% higher among people with neuromyelitis optica spectrum disorder (NMOSD) compared with matched people without the neurological condition, a study found.

Results suggest that the risk of diabetes is particularly high in NMOSD patients who have receive treatment with steroids, suggesting this risk may be at least partially due to their side effects.

The data, however, showed no increased risk of type 2 diabetes among people with multiple sclerosis (MS), which like NMOSD is an inflammatory disorder that affects the brain and spinal cord and may be treated with steroids.

“This study found that patients with NMOSD had an increased incidence rate of T2DM [type 2 diabetes], whereas patients with MS did not,” the researchers wrote. “However, the elevated T2DM risk was specifically associated with prolonged or frequent steroid use, leaving uncertainty about its direct link to NMOSD.”

The study, “The risk of type 2 diabetes mellitus in multiple sclerosis and neuromyelitis optica spectrum disorder: a nationwide cohort study,” was published in Multiple Sclerosis and Related Disorders.

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Study looked at risk for MS, NMOSD patients

Diabetes is a metabolic disorder characterized by abnormalities in how the body processes sugar. Type 1 diabetes is caused by an autoimmune disorder that damages the pancreas, whereas type 2 diabetes is marked by abnormalities in the body’s response to insulin, a hormone necessary for cells to take in sugar from blood.

Prior research has suggested an increased risk of type 1 diabetes in MS patients, but there’s been little investigation into the risk for type 2 diabetes, which is more common in the general population. And no study had assessed the risk of developing type 2 diabetes in people with NMOSD.

A team of scientists in South Korea set out to investigate the relative risk of type 2 diabetes in MS and NMOSD patients by analyzing data from the Korean National Health Insurance Service, a public program that provides health insurance for 97% of the country’s population.

The scientists identified 1,801 adults with MS and 1,721 with NMOSD who did not have diabetes at an initial visit. All were at least 20 years old, and about half the patients in each group were 40-64.

Over an average follow-up time of more than four years, 99 of the MS patients and 94 of the NMSOD patients — or about 0.5% of all patients in each group — were diagnosed with type 2 diabetes.

To compare these rates to the general population, the researchers used a case-control design. For each MS and NMOSD patient, they selected five people from the general population who had no neurological disorder but had otherwise similar demographic and clinical characteristics. These included age, sex, presence/absence of high blood pressure, and presence/absence of abnormal levels of fatty molecules in the blood. These controls were also followed for more than four years.

Results showed no difference in rates of type 2 diabetes between MS patients and their matched controls. But there was a difference for NMOSD: Patients with this disease were 54% more likely to develop type 2 diabetes than their matched controls. The risk was particularly high, by twofold, for NMOSD patients with substantial physical disability.

“This population-based cohort study found that the risk of developing T2DM was 1.54 times higher in patients with NMOSD than in control populations,” the researchers wrote.

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A complicated picture

Further analyses showed that the risk of type 2 diabetes was significantly elevated, by about 77%, among NMOSD patients who had received treatment with anti-inflammatory steroids. “A significant increase in T2DM risk was observed specifically in those with a steroid duration surpassing 101 days—the median day of steroid use,” the team wrote.

For NMOSD patients who hadn’t been treated with steroids, there was a trend towards a lower risk of type 2 diabetes, but this wasn’t statistically significant.

As steroids are known to cause metabolic side effects, including blood sugar abnormalities, the researchers speculated that use of these medications may be a reason for the increased risk of type 2 diabetes in some NMSOD patients.

They cautioned, however, that it’s hard to draw solid conclusions about cause and effect, especially given that patients treated with steroids likely had more active inflammation than those who weren’t, and inflammation may also influence diabetes development.

The researchers also noted that steroid use was not linked with a heightened risk of diabetes in MS patients, further complicating the picture.

“Further investigations are warranted to validate the increased risk of T2DM in NMOSD and to gain a deeper understanding of the underlying mechanisms,” the team concluded.