Dementia Study: Many Taking Alzheimer's Drugs May Not Have Disease

Interim study findings show a significant portion of people with mild cognitive impairment or dementia taking medication for Alzheimer's may not actually have the disease, the Washington Post reports.

Presented Wednesday at the Alzheimer's Association International Conference in London, the results come from a four-year study testing over 18,000 Medicare beneficiaries to see if their brains contain the amyloid plaques that are one of the two hallmarks of the disease.

According to the preliminary findings, among 4,000 people tested so far in the Imaging Dementia-Evidence for Amyloid Scanning study, researchers at the University of California at San Francisco found just 54.3 percent of MCI patients and 70.5 percent of dementia patients had the plaques.

A positive amyloid test doesn't mean someone has Alzheimer's, but its presence precedes the disease and increases the risk of progression. A negative test definitively means a person does not have it.

"If someone had a putative diagnosis of Alzheimer's disease, they might be on an Alzheimer's drug like Aricept or Namenda," James Hendrix, the Alzheimer Association's director of global science initiatives who co-presented the findings told the Post.

"What if they had a PET scan and it showed that they didn't have amyloid in their brain? Their physician would take them off that drug and look for something else."

"We thought we would be able to see about a 30 percent change, but we're getting a 66 percent change, so it's huge," Hendrix said. "We see high percentages of people who are on a drug and didn't need to be on those drugs."

For decades, diagnosing Alzheimer's was not possible until an autopsy was performed.

Now, a spinal tap, which is an invasive procedure, or PET scan — which is expensive and typically not covered by insurance – can detect the telltale amyloid deposits. Researchers are trying to develop a simple blood test to do so, the Post reported.

According to the Post, the Centers for Medicare & Medicaid Services agreed to fund the bulk of the $100 million IDEAS study – and researchers hope positive results will persuade them to cover it in the future.

• Brain Scans May Change Care for Some People with Memory Loss
• Hearing Is Believing: Speech May Be a Clue to Mental Decline