A study of more than half a million patients taking certain medications for diabetes found they had a 22% reduced risk of developing dementia. The drugs, called thiazolidinediones or TZDs, work by reducing bad cholesterol, allowing more blood flow to the brain.

According to Study Finds, people with Type 2 diabetes are generally more prone to develop the neurological disease because of poor blood circulation.

“Type 2 diabetes is associated with elevated risk of all cause dementia, including its two main subtypes, Alzheimer’s disease and vascular dementia,” said lead author Dr. Jin Zhou, from the University of Arizona. TZDs work by targeting insulin resistance to improve blood glucose levels. They also lower blood pressure.

The authors stated in a news release that this older class of drugs may effectively prevent dementia in patients at high risk who have mild or moderate Type 2 diabetes, since both conditions share some of the same physiological patterns.

The scientists analyzed the electronic records of 559,106 men and women diagnosed with Type 2 diabetes from the national Veteran Affairs (VA) Health system, spanning the period from January 2000 to December 2019. They studied the data to compare dementia risk in older people with Type 2 diabetes who were treated with either a sulfonylurea (SU) or a TZD with those treated with metformin (MET) alone.

The study participants' health was tracked for an average of nearly eight years. After at least one year of drug treatment, the use of a TZD alone was associated with a 22% lower risk for dementia from any cause, compared with the use of metformin alone, says the news release. More specifically, use of a TZD was associated with an 11% lower risk for Alzheimer’s disease and a 57% reduced risk for vascular dementia.

By comparison, the risk for dementia from any cause was 11% lower for people taking both metformin and TZD. Dementia risk was 12% higher for those using a sulfonylurea drug alone. The researchers suggested that supplementing a sulfonylurea with either metformin of a TZD may offset that risk.

Furthermore, the scientists found that people younger than 75 reaped more benefits from using a TZD than older patients, which highlights the importance of potentially using this drug to prevent dementia. TZDs also appeared to be more protective in overweight or obese patients, says Study Finds.

“This may result as TZD reduces central obesity, a recognized risk factor for dementia,” said the researchers.

“In summary, TZD users had a lower risk of dementia, and SU users had a higher risk of dementia than MET users,” concluded Zhou. “Future studies for repurposing oral anti-diabetic agents for dementia prevention may consider prioritizing TZDs. SU users could be at an elevated risk of dementia, compared with MET or TZD users.”