TUESDAY, Aug. 27, 2024 (HealthDay News) -- People with multiple sclerosis appear to have a lower risk of developing Alzheimer’s disease, a new study suggests.

MS patients are far less likely to have elevated blood levels of toxic proteins that form amyloid plaques in the brains of people with Alzheimer’s, researchers report.

“Our findings imply that some component of the biology of multiple sclerosis, or the genetics of MS patients, is protective against Alzheimer’s disease,” said lead researcher Dr. Matthew Brier, an assistant professor of neurology and radiology with Washington University School of Medicine in St. Louis.

“If we could identify what aspect is protective and apply it in a controlled way, that could inform therapeutic strategies for Alzheimer's disease,” Brier added in a university news release.

Researchers undertook the study after noticing that MS patients under their care didn’t develop Alzheimer’s as they grew older, even if they had a family history of the disease.

“I noticed that I couldn't find a single MS patient of mine who had typical Alzheimer’s disease,” said senior researcher Dr. Anne Cross, chair of neuroimmunology at the Washington University School of Medicine.

“If they had cognitive problems, I would send them to the memory and aging specialists here at WashU Medicine for an Alzheimer’s assessment, and those doctors would always come back and tell me, ‘No, this is not due to Alzheimer’s disease,’” Cross said.

For the study, researchers recruited 100 MS patients to take a blood test that’s proven highly effective at predicting the presence of amyloid plaques in the brain. Their results were compared to those from a group of 300 people without MS.

The accumulation of amyloid plaques is a hallmark of Alzheimer’s, even though it’s not clear how the plaques contribute to the brain decline seen in those with the disease, researchers said.

“We found that 50% fewer MS patients had amyloid pathology compared to their matched peers, based on this blood test,” Brier said.

Brain scans revealed that the more typical a patient’s MS history, the less likely they were to have amyloid plaques accumulating in their brains.

This suggests there’s something about MS itself that is protective against Alzheimer’s, they noted.

During flare-ups of MS, the immune system turns on a person’s central nervous system. This causes MS symptoms by damaging the insulating myelin sheath that protects nerve cells.

It’s possible this immune activity also somehow reduces amyloid plaques in MS patients’ brains, researchers said.

“Perhaps when the Alzheimer’s disease amyloid pathology was developing, the patients with MS had some degree of inflammation in their brains that was spurred by their immune responses,” Brier said.

Brier noted that microglia -- cells that serve as a first line of immune defense in the brain -- have been shown to clear amyloid from the brain of lab animals.

Researchers next plan to figure out the genetics behind what they’ve discovered, and to test amyloid plaque development in lab animals with MS.

The new study was published recently in the Journal of Neurology.

More information

The National Institutes of Health has more about multiple sclerosis.

SOURCE: Washington University School of Medicine, St. Louis, news release, Aug. 23, 2024