Researchers at the University of California at Los Angeles, the University of California at San Francisco and Boston College tracked 6,836 American women born between 1935 and 1956 across about 20 years. Participants were enrollees in the Health and Retirement Study, a federally funded long-term observational study of aging people across the United States.
In the past decade, research has increasingly suggested that controllable lifestyle factors — including regular mental stimulation provided by work — can minimize the risk of cognitive decline.
Elizabeth Rose Mayeda, a professor at UCLA and the lead author of the study, said her findings, especially if confirmed by further research, point to the importance of policies and programs that incentivize women’s participation in the workforce.
“Paid leave, affordable child care, equal pay for equal work — all of these things could help improve women’s health in later life,” she said.
The majority — almost two-thirds — of the 5.8 million Americans with Alzheimer’s are women, according to the 2019 Alzheimer’s Disease Facts & Figures Report. Heather Snyder, the senior director of medical and scientific operations at the Alzheimer’s Association, said the UCLA study is “a piece of the puzzle” in understanding why the disease is more prevalent among women.
“The workforce has changed and so has the type of employment women have engaged in over the last 100 years, and we don’t know how that might impact our brain health,” Snyder said. “This is one of the first studies to look at that, so it’s really interesting to see the results.”
Participants — all of them 50 or older at the start of the study — reported their parental and marital status and whether they worked for a wage between their mid-teens and middle age. Then, researchers gave each woman a memory assessment every two years for about two decades.
The memory test asked whether the women could remember a list of words several minutes after they first heard it. It’s a “standard memory performance evaluation” in research studies, Mayeda said.
The group examined, which was nationally representative racially, included working non-mothers, working married mothers, working single mothers, nonworking married mothers and nonworking single mothers.
Mayeda and her team found that average memory performance between 60 and 70 declined 61 percent faster for married mothers who never worked than for married mothers who did work. And they found that memory performance in the same age category declined 83 percent faster for women who spent a long time as single mothers without paid employment, as compared to married women who worked.
Among married mothers who worked, the rate of memory loss did not vary according to whether participants worked continuously, took a few years off to raise their children or took many years off to raise their children, Mayeda said. What was important, she said, was that they worked for a wage at some point.
Mayeda said the UCLA team is not recommending a clear recipe — work for this long, at this time of life — to stave off dementia.
“We can’t say based on our study for sure what is the exact key period,” she said. “It just seems to be that being engaged in the paid labor force is protective. You don’t need to spend your entire lifetime working.”
Mayeda and Snyder emphasized that the study’s results do not mean all stay-at-home mothers should find paid work to avoid dementia.
For one thing, memory decline in old age does not necessarily lead to Alzheimer’s; it merely means that someone has “a higher risk of the disease,” Mayeda said. For another, Mayeda and Snyder suggested that it could be possible to create some of the health benefits provided by working at home.
Mayeda said it is not clear why paid employment would protect against memory loss, but noted that previous research suggests that mental sharpness in later life is linked partly to “cognitive stimulation and social benefits” — both things encountered in the workplace.
Still, you may be able to replicate that in the house by regularly doing things such as reading a newspaper, doing crossword puzzles and spending time with neighbors, Mayeda said. She said the study does not have to be “bad news for stay-at-home moms.”
Said Snyder: “I think what it gets to, is thinking about what are the behaviors that we should be doing, it’s not so much wage-earning versus non-wage-earning.”
One behavior to shun — if you want to avoid dementia — is taking sleep medication. Another study presented at the conference Monday and conducted by researchers at the University of California at San Francisco found that white adults who “often” or “almost always” take sleeping pills are 43 percent more likely to develop dementia than white adults who “rarely” or “never” use sleep medication.
Meanwhile, research led by the University of Cincinnati and also presented at the conference found that people with dementia suffer epileptic seizures up to 6 1 / 2 times more often than do people without the disease.
About 50 million people have dementia worldwide, and that number is projected to triple by 2050, according to the 2018 World Alzheimer Report. The worldwide cost of dementia in 2018 was about $1 trillion, a figure expected to double by 2030.
The UCLA study did not ask women what kind of employment they engaged in or what salary they earned. Mayeda pointed to a 2018 study, published in the Journal of Epidemiology and Community Health, that showed that more demanding jobs led to higher cognitive performance in late life for both men and women.
“As our next steps, we could look at the type of work,” she said. “It would be really, really interesting to drill down into that.”