Nearly two-thirds of the 5.8 million people living with Alzheimer’s disease in the United States are women. The reason seemed obvious: Women outlive men in this country by an average of five years, and advancing age is the biggest risk factor for Alzheimer’s and other dementias. But research by Elizabeth Rose Mayeda, an epidemiologist in the UCLA Fielding School of Public Health, raises the possibility that other factors also might be involved.

Mayeda, with colleagues from UC San Francisco and Boston College, found that women who participated in the paid workforce during early adulthood and middle age experienced a slower rate of memory decline later in life than women who didn’t. Memory loss is among the first signs of dementia.

Mayeda’s group analyzed data from the national Health and Retirement Study, in which more than 6,000 women born between 1935 and 1956 reported on their work history and marital and parental status between the ages of 16 and 50. When the women were 50 or older, they took memory-performance tests every two years. The group found that among married mothers, the average memory performance for those between ages 60 and 70 who had never engaged in paid employment declined at a 61% faster rate than those who had.

Women who experienced a prolonged period of single motherhood without waged employment experienced an 83% faster decline than married mothers who worked.

The good news is that the study suggests women don’t have to work the entire period from ages 16 to 50 to reap the rewards: Those in the study who took time away from work — when their children were young, for example — showed similar trajectories as those who didn’t. The same might apply to other interruptions — like unemployment in the wake of the coronavirus pandemic — in paid work for women.

The Health and Retirement Study wasn’t designed to draw conclusions on how paid work might contribute to better later-life cognitive health, but Mayeda says previous research suggests higher levels of mental stimulation and social engagement help keep the mind sharp and replicate the cognitive benefits of work. “Understanding the mechanisms linking paid labor-force participation and later-life cognitive health will help illuminate possible strategies to promote later-life cognitive health,” Mayeda says.

She hopes her future research will further clarify what’s driving the association between work and later-life cognitive health among U.S. women. In the meantime, Mayeda believes her findings underscore the potential value of policies that support women who choose employment: equal pay for equal work, paid family leave and affordable child care.

“Certainly, women living longer than men plays a significant role in the disproportionate number of women with Alzheimer’s disease in the U.S.,” Mayeda says. “But even if that’s the only reason, it highlights the need to study the factors that influence dementia risk for women.”