Older adults with a positive attitude towards ageing may be less likely to develop dementia, even if they are genetically predisposed to it, a study from the United States has found.

Researchers at Yale University studied a group of more than 4,000 adults aged 60 and above and found those who held positive beliefs about ageing had a 44 per cent lower risk of developing dementia than those who held negative beliefs.

The risk was even lower — almost halved — among people with a genetic predisposition to dementia.

"We found that those who had more positive age beliefs were less likely to develop dementia, even if they were at a higher risk," lead author Becca Levy said.

Professor Levy said the study, published today in PLOS ONE, suggests that positive age beliefs may act as a "protective factor" against dementia, supporting the case for a public health campaign against ageism.

"Age beliefs are something that we have shown in other studies to be malleable. So, I think they're a promising factor to look at," she said.

Risk measured against attitude

Dr Levy and her colleagues at Yale School of Public Health recruited 4,765 "dementia free" American adults with an average age of 72.

The first step was to assess the participants' attitudes towards ageing, before assessing them every two years on a range of cognitive skills to determine whether they had developed dementia.

"We were interested in knowing whether the age beliefs they had taken in from their surrounding culture influenced their risk of developing dementia," Professor Levy said.

Participants' beliefs about ageing were assessed using an "Attitude toward Ageing" scale, in which they were asked about the degree to which they agreed or disagreed with statements such as, "The older I get, the more useless I feel".

"If somebody strongly agreed with that statement, for example, they would be given a score that indicates they have a more negative belief about ageing. But if they disagreed, then they would receive a score that indicates a positive view of ageing," Professor Levy said.

To assess the potential effects on people genetically predisposed to dementia, 26 per cent of people included in the sample were carriers of the APOE-e4 gene variant, one of the strongest risk factors for dementia — affecting about one-quarter of the US population (and one-fifth of Australia's).

Positive beliefs lower risk

The researchers found overall, participants holding positive beliefs about ageing had a 43.6 per cent lower risk of developing dementia over the course of four years, compared to those holding negative beliefs.

Among those with the APOE-e4 gene variant, the difference was even more pronounced: those holding positive beliefs had a 49.8 per cent lower risk of developing dementia compared to their high-risk counterparts holding negative beliefs.

"We found that positive age beliefs can reduce the risk of one of the most established genetic risk factors of dementia," Professor Levy said.

The results took account of other factors that could influence the findings, including age, education, sex, race, cardiovascular disease, diabetes and baseline cognitive performance.

"So, it was above and beyond those factors that we found age beliefs contributed to likelihood of developing dementia," she said.

Stress may explain why

According to Professor Levy, studies suggest the mechanism by which age beliefs may influence the development of dementia is likely to involve stress.

"We've found that individuals who have more positive age beliefs … have lower levels of stress.

"Conversely, those who have more negative age stereotypes seem to have an exacerbated response to stress," she said.

"Others have found that stress can be related to the development of dementia," she added.

"So, our thinking is that it's possible that stress is part of the mechanism in what we're observing in this study."

Study needs to be replicated, expert says

Henry Brodaty, co-director of the Centre for Healthy Brain Ageing at University of New South Wales, said the researchers had made "quite a significant finding".

"This is a big study … and the sample has been well studied," he said.

However, Professor Brodaty noted, the results should be interpreted with some caution because the diagnostic tool used to identify patients with dementia — a short telephone interview — was not the gold standard for diagnosing dementia.

"There are some concerns about using that as a diagnostic tool itself … it's a proxy for a proper clinical assessment, so that's one caveat," Professor Brodaty said.

He said the next step would be to replicate the study and possibly do an intervention trial — to work out whether changing someone's beliefs about ageing would have an effect on their risk of developing dementia.

"It may be people who are developing dementia, but haven't yet manifested it clinically, have got negative attitudes because of their dementia, not the other way around," he said.

"We don't know yet whether changing beliefs will make a difference … if you could show that, then that would be interesting."