MONDAY, Jan. 23 (HealthDay News) -- People who engage in activities such as reading and playing games throughout their lives may be lowering levels of a protein in their brains that is linked to Alzheimer's disease, a new study suggests.

Although whether the buildup of the protein, beta amyloid, causes Alzheimer's disease is debatable, it is a hallmark of the condition, the researchers noted.

"Staying cognitively active over the lifetime may reduce the risk of Alzheimer's by preventing the accumulation of Alzheimer's-related pathology," said study author Susan Landau, a research scientist at the Helen Wills Neuroscience Institute at the University of California, Berkeley.

"Some of the literature has hypothesized this finding, but this is the first study to report that lifetime cognitive activity is directly linked to amyloid deposition in the brain," she said. "We think that cognitive activity is probably one of a variety of lifestyle practices -- occupational, recreational and social activities -- that may be important."

The report was published in the Jan. 23 online edition of the Archives of Neurology.

In the United States, more than 5 million people have Alzheimer's disease, and it is now the sixth-leading killer in the country, according to the researchers. No cure exists for the neurodegenerative condition, but a draft of the first-ever National Alzheimer's Plan released last week laid out plans by the federal government to have effective treatment by 2025.

For the study, Landau's team used a special imaging technique called positron emission tomography, which is able to see beta amyloid plaque in the brain, plus neuropsychological tests to see what effect cognitive stimulation might have on Alzheimer's risk.

The tests were done on 65 healthy people, average age of about 76. In addition, they tested 10 patients with Alzheimer's disease whose average was nearly 75 and 11 young people who were an average of about 25 years old.

"We interviewed them about their lifetime participation in cognitively stimulating activities," said lead researcher Dr. William Jagust, a professor of neuroscience also at the Helen Wills Neuroscience Institute.

The researchers found that people who engaged in brain-stimulating activities, particularly when they were young and middle-aged, had the least amount of beta amyloid.

Those older adults who reported the most activity had amyloid levels similar to those young individuals, while those who engaged in the least such activities had amyloid levels similar to the Alzheimer's patients.

"This study suggests that not only does it reduce your risk of Alzheimer's disease, but it may affect the pathological process itself," Jagust said.

Why this kind of mind stimulation reduces the amount of beta amyloid isn't known, he added.

"The environment may affect the amount of amyloid that's deposited," he said. "This kind of lifetime cognitive activity may make people's brains more efficient. And if your brain is functioning better, it's possible that would result in producing less of this amyloid," he explained.

"Cognitive activity seems to have powerful effects on the brain," Jagust said. "Lifestyle can have a profound effect on the basic biology of Alzheimer's disease."

The size of the effect isn't known nor is the size of the reduction in risk for Alzheimer's disease, he noted.

Greg M. Cole, associate director of the Alzheimer's Disease Research Center at the University of California, Los Angeles, said that "a number of studies have suggested that increased education or cognitive activity associates with reduced risk for Alzheimer's."

"So if you have more wits to begin with, you can afford to lose more before you become impaired," he said.

However, this new study reports something different, namely that higher cognitive activity in young and middle-aged adults is associated with lower levels of Alzheimer's pathology, Cole said.

"There may be a plausible theory for this because increased brain use increases fitness and reduces the amount of brain activity required to execute a task, and production of the beta amyloid toxin is associated with brain activity. This is an interesting new finding that may have serious implications," he said.

Another expert, Dr. Sam Gandy, the Mount Sinai Professor of Alzheimer's Disease Research at Mount Sinai Hospital in New York City, added that "this new study jibes well with other existing epidemiological studies in which social engagement has been linked to successful cognitive aging on purely clinical grounds."

"There is also a link between physical activity and reduced risk for Alzheimer's, and one would guess that physical exercise might well delay onset of Alzheimer's if exercise were begun years before cognitive decline developed, but this is yet to be established," Gandy said.

More information

For more information on Alzheimer's disease, visit the Alzheimer's Association.