Work longer, stay sharper

She is hardly alone.

With 401(k)s looking more like 201(k)s these days, many baby boomers are putting off retirement to rebuild decimated nest eggs. But amid such uncertainty there may be hope: A number of studies suggest that staying mentally and socially active may help stave off dementia and other dreaded declines associated with aging.

One tantalizing British study, in particular, recently concluded that working beyond normal retirement age appears to keep dementia at bay.

“Probably the way things are going, I will never retire,’’ said Agnew, who has been working seven days a week in her ARTmosphere Gallery in the North End since laying off several workers earlier this year.

“I would like to slow down a little more,’’ she said, “but the way things are, I am speeding up.’’

Symptoms of Alzheimer’s disease first emerged in Agnew’s father three years after he retired at 65. He died of the disease at 83. Now, Agnew’s decision to continue working may confer a double-barreled benefit: a fatter nest egg and, if the recent British study holds true, a longer period of health.

The British researchers scoured medical records of 382 men whose Alzheimer’s symptoms emerged around age 75. They found that, all other factors being equal, the symptoms were delayed about seven weeks for each extra year the men worked.

“It is possible to affect onset of dementia by lifestyle choices later in life,’’ the study’s lead author, Michelle K. Lupton, a graduate student at the Institute of Psychiatry, King’s College London, said in a phone interview.

Lupton said that the group’s findings, published in May in the International Journal of Geriatric Psychiatry, shouldn’t be interpreted as a prescription to work years longer to avoid Alzheimer’s. Rather, she said, their conclusions add weight to the “use it or lose it’’ hypothesis of staying mentally engaged to slow the negative effects of aging.

While the researchers only looked at the link between retirement and Alzheimer’s in men, Lupton said similar findings would likely apply to women.

Some scientists believe a trait called cognitive reserve may help explain why certain people are able to stay mentally sharper longer than others. The term applies to the brain’s resilience, its ability to cope with damage - such as the signature plaque that clogs the brain in Alzheimer’s - while still functioning normally.

Exposure throughout life to mentally challenging activities - such as pursuing an education, working at an engaging job, and volunteering - may contribute to building cognitive reserve, said Yaakov Stern, professor of clinical neuropsychology at Columbia University and a member of the Alzheimer’s Association’s Medical and Scientific Advisory Council.

A robust cognitive reserve, Stern added, may also help people cope with normal impairments of aging, such as memory problems.

The way such a reserve is built up can vary among individuals.

“Any kind of enrichment is valuable, and working, for most people, is socially and intellectually stimulating,’’ he said.

“We know more social engagement is good, but I can’t just say take one class a week and that will be good for you,’’ Stern said. “We are not sure what the recipe is.’’

But the jury is still out about the effectiveness of brain exercise products - often sold as computer-based games and estimated to be an $80 million per year industry.

Researchers at Lifespan, a Rhode Island-based healthcare nonprofit, reviewed all of the existing trials on such products and concluded in a study published in Alzheimer’s & Dementia this spring that none showed evidence of delaying or slowing the decline of cognitive skills, such as memory.

On one point there is no question: Since the start of the recession, more people nearing or just past retirement age have opted to stay in the workforce. Polina Vlasenko, a researcher at the American Institute for Economic Research, analyzed years of national data and found that the labor force participation rate of people ages 54 to 69 is now at the highest levels on record.

“It is likely that people close to or past retirement age feel the need to work because their retirement savings have suffered in the recent financial crisis,’’ she concluded in her May study.

In an AARP survey released last fall, financial need was cited by older Americans as the number one reason for staying in the workforce, but many said they stayed for social and psychological reasons. Roughly 20 percent of those surveyed gave nonfinancial considerations, such as enjoying work or appreciating the sense of usefulness it provides, as their primary reasons.

“People feel they still have a lot to give back, skills and knowledge they want to contribute to the workforce,’’ said Deborah Russell, director of workforce issues at AARP, a national nonprofit that represents people over 50.

“There is a correlation between retirement and not using certain parts of the brain that you may use for work, such as reasoning and negotiation,’’ she said.

Yet staying past retirement at a job that is stressful, not fulfilling, or socially engaging is unlikely to aid healthy aging.

“Your risk of dementia is increased by hypertension and diabetes and levels of stress, so if your work increases those things, staying there would have an opposite effect,’’ said Lupton, the British researcher whose study found some protections against dementia among workers who stayed on the job longer.

“The bottom line,’’ Lupton said, “is keep an active brain and low stress. That’s the take-home message from lots of studies.’’

Kay Lazar can be reached at klazar@globe.com.