There was an “abrupt decline” in the percentage of older Americans reporting serious problems with concentration, memory and decision-making over a dec­ade — particularly among women, says a new study.

Researchers are heralding the findings as “very welcome” news.

From 2008 to 2017 the percentage of adults ages 65 and older in the U.S. with serious cognitive issues dropped to 10% from 12.2%, researchers from Canada found. In a hypothetical scenario without the decline, about an additional 1.1 million older people in the U.S. would have reported experiencing mental congestion.

And older women appeared to drive much of the plunge.

Serious cognitive problems declined 23% over a decade among women in the age group, compared with 13% among men, the study, published last month in the Journal of Alzheimer’s Disease, found.

The findings were based on 10 annual “American Community Surveys” conducted by the U.S. Census Bureau that included a total of 5.4 million people in the U.S. ages 65 and older.

“We were astonished to see the prevalence of cognitive impairment decrease so sharply over such a short period of time,” study lead author Esme Fuller-Thomson, director of the University of Toronto’s Institute for Life Course & Aging, said in a news release. “This decline in the prevalence of serious cognitive problems has a cascade of benefits for older adults, their families and caregivers, the health and long-term care system and the whole U.S. economy.”

Further research showed each additional year of formal education study parti­cipants had resulted in a lower risk of developing dementia, an umbrella term that includes several diseases and conditions that cause debilitating impairments in memory and concentration.

The Centers for Disease Control and Prevention says cognitive decline is one of the earliest “noticeable” symptoms of dementia, including Alzheimer’s disease.

Researchers said 60% of the decline in serious cognitive issues “was attributable to generational differences in educational attainment.”

“It appears that these increasing educational opportunities continue to pay dividends more than half a century later,” said study co-author Katherine Ahlin, a recent graduate student of social work at the University of Toronto. “The short-term benefits of increasing educational attainment for income, productivity and the economy are well documented, but our research suggests the long-term benefits on later-life cognitive functioning are substantial.”

But education cannot explain the entirety of the decline in cognitive issues among older people, researchers said.

It’s possible that better nutrition, declines in smoking and the phaseout of leaded gasoline — which research has connected to increased rates of dementia — also contributed to the “positive trends.”

“Our finding from this study of over 5 million older Americans is definitely a very welcome, ‘good news story’ indicating a steep decline in the prevalence of cognitive impairment among older Americans,” Fuller- Thomson said. “We still need to investigate whether these positive trends will continue in the decades ahead and why men’s rates of improvements are lagging behind those of women.”

Although the study offers good news, other research suggests the opposite will occur over time.

A 2018 CDC study estimated the number of people in the U.S. with Alzheimer’s disease and other forms of dementia will grow to 14 million from about 6 million by 2060. Researchers largely cited population growth among communities of color, particularly Hispanic people, for the increase because dementia disproportionately affects nonwhite racial and ethnic groups.

“Early diagnosis is key to helping people and their families cope with loss of memory, navigate the health care system and plan for their care in the future,” the CDC said.