MONDAY, Dec. 7, 2015 (HealthDay News) -- Young and middle-aged adults who harbor negative thoughts about aging may face a higher risk for Alzheimer's disease decades later, new research suggests.
The investigation compared early attitudes on aging expressed by dementia-free adults to Alzheimer's-related brain changes nearly 30 years later.
"What we found is that negative perceptions on aging are definitely significantly related to [Alzheimer's] disease indicators," said study lead author Becca Levy, an associate professor at the Yale School of Public Health in New Haven, Conn.
But why? Levy said the study wasn't designed to answer that question.And the study only found a link between stereotypes about aging and later Alzheimer's risk.
But Levy speculated that it could be that a pessimistic stance on aging drives up stress. And stress, in turn, drives up Alzheimer's risk, she said.
"Regardless, the positive message here is that our thinking about aging is modifiable," she said. "It can be changed. So if we can reduce ageism, and promote more-positive views on getting older, it could perhaps be one way to reduce Alzheimer's risk."
Another expert doubts that stress alone is the culprit.
More research is needed to understand the association, said Dr. Amy Kelley, an associate professor in the Brookdale department of geriatrics and palliative medicine at the Icahn School of Medicine at Mount Sinai in New York City.
It's an "interesting association, but it's very hard to interpret, because there's a really wide range of things, besides stress, that could be involved," said Kelley.
"Maybe those with more-negative views don't bother exercising. Or maybe they eat less well," she pointed out. "There could be a myriad of pathways that play a role."
Alzheimer's is a progressive brain disorder that affects more than 5 million Americans, most of them older than 65, according to the Alzheimer's Association.
The study findings were published in the Dec. 7 online edition of Psychology and Aging.
The research team first focused on more than 50 men and women who were dementia-free when they enrolled in the large, multi-decade Baltimore Longitudinal Study of Aging. That project, launched by the U.S. National Institute on Aging in 1958, is the longest running American study on aging.
Years later, all participants underwent annual brain-imaging scans (MRIs) for up to 10 years, with an average of seven scans per person. The goal was to pinpoint any changes in the size of the hippocampus region of the brain, an area known to play a critical role in memory regulation.
Scan results were then paired against the views each participant had offered about a quarter-century earlier to 16 age stereotypes, such as "old people are absent-minded."
Over the course of a decade, the scans showed all participants experienced at least some decline in the size of their hippocampus. However, even after accounting for factors such as age, education and gender, those who had held grimmer views on aging decades earlier experienced significantly greater size reductions than more-optimistic respondents, the researchers found.
Moreover, adults who subscribed to more-negative age stereotypes were found to experience the same degree of hippocampus shrinkage in three years as those with more-positive views experienced in nine years.
The research team also performed brain autopsies on 74 participants who died at an average age of about 89. About three-quarters were men, and all were 60 and older.
The autopsy examiners looked for two well-known markers for Alzheimer's disease: protein clusters known as amyloid plaques, and twisted protein strands known as tangles.
Plaque and tangle presence was then correlated with the attitudes on aging the deceased participants had expressed nearly three decades before.
Again, those who held more-negative views on aging early on were found to have a significantly greater presence of plaques and tangles, the study authors said.
There's more on Alzheimer's risk at the Alzheimer's Association.