People with plaque in the brain associated with Alzheimer's disease may have a greater risk for cognitive impairment than those who have a gene tied to the dementia-causing illness, Australian researchers have found.

In a study of 141 healthy subjects, those with clumps of amyloid beta plaque in their brains at the start had as much as a 20 percent greater decline in memory and thinking over an 18-month period than those with fewer plaques. The research also showed that patients with the gene linked to Alzheimer's, called ApoE4, had a greater mental decline, though having the gene didn't alter the decline related to the plaques.

The findings, published yesterday in the journal Neurology, suggest that brain plaques may be a more important factor in determining the risk of Alzheimer's than the gene, said Yen Ying Lim at Florey Institute of Neuroscience and Mental Health in Melbourne, who led the study. More than a century after Alzheimer's was first identified, scientists have yet to find a cause or a cure.

"If you have high amyloid, whether you have the gene or not seems to not really affect that," Lim said. "This could provide us with a platform to begin to investigate whether drugs designed to stop amyloid accumulation in the brain can actually prevent people from getting to the more severe stages of the disease."

An estimated 36 million people worldwide suffer from Alzheimer's disease.

The Australian study involved healthy adults with an average age of 76 who were free of problems in memory and thinking.They were tracked for 18 months using computer-based cognitive tests based on playing card games and remembering word lists. They also underwent PET brain scanning and were tested for the ApoE4 gene, which is found in about half of Alzheimer's patients.

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