A common blood test can flag early Alzheimer’s disease patients who are four times more likely to experience rapid brain decline, a new study says.

The test — the triglyceride-glucose (TyG) index —assesses a person’s level of insulin resistance and can estimate their risk of developing Type 2 diabetes.

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But the test also can help determine which people newly diagnosed with Alzheimer’s might experience a faster decline in brain function, researchers reported at the European Academy of Neurology’s annual meeting.

“Once mild cognitive impairment is diagnosed, families always ask how fast it will progress,” lead investigator Dr. Bianca Gumina, a neurology resident at the University of Brescia’s Brain Health Center in Italy, said in a news release.

“Our data show that a simple metabolic marker available in every hospital laboratory can help identify more vulnerable subjects who may be suitable candidates for targeted therapy or specific intervention strategies,” she added.

Insulin resistance has been linked to the onset of Alzheimer’s, but its role in how quickly the disease progresses has received less attention, researchers said in background notes.

For the study, researchers reviewed medical records for 315 non-diabetic patients in cognitive decline, including 200 with confirmed Alzheimer’s disease.

All underwent the TyG index blood test and were followed for three years.

The third of Alzheimer’s patients with the highest levels of insulin resistance had a quadrupled risk of faster cognitive decline, when compared to those with the least insulin resistance, results show.

“We were surprised to see the effect only in the Alzheimer’s spectrum and not in other neurodegenerative diseases,” Gumina noted. “It suggests a disease-specific vulnerability to metabolic stress during the prodromal window, when interventions may still change the trajectory.”

Insulin resistance is believed to advance Alzheimer’s by impeding blood sugar uptake to neurons, promoting accumulation of toxic beta amyloid proteins, disrupting the blood-brain barrier and fueling inflammation, researchers said.

This study found that high TyG-assessed insulin resistance was indeed associated with disruption to the blood-brain barrier, researchers said.

However, insulin resistance did not appear to interact with a person’s genetic risk for Alzheimer’s, indicating that these are separate risk factors that might operate independently.

Researchers now are investigating whether TyG levels track with imaging scans of Alzheimer’s, as combining the two could aid earlier detection.

“If targeting metabolism can delay progression, we will have a readily modifiable target that works alongside emerging disease-modifying drugs,” Gumina said.

She presented her findings Monday at the EAN meeting in Helsinki.

Findings presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.