Studies have shown a connection between menopause and cognitive decline, but researchers wanted to understand what happens in the long term. Does earlier menopause set the stage for faster memory decline, an earlier Alzheimer's disease diagnosis or changes in brain structure as women age?

To trace this connection, they analyzed data from 2,603 older women enrolled in two long-running studies—the Religious Orders Study and the Rush Memory and Aging Project—and followed them for up to 18 years.

Women who went through menopause earlier faced faster mental decline overall, especially when it came to episodic memory, like recalling personal events and experiences. They also developed Alzheimer's disease at a younger average age. To put this in perspective, reaching menopause 10 years earlier translated to roughly 1.8 fewer Alzheimer's disease-free years at the average age of diagnosis.

The unequal burden of hormones

Women in their 60s are nearly twice as likely as men to develop Alzheimer's disease, a difference that cannot be explained by women living longer alone. One possible piece of the puzzle is menopause. This phase marks a major shift in biological aging as the body stops producing the ovarian hormone estrogen, which is crucial to maintaining brain health, brain function, energy metabolism and inflammation. Losing this protective effect could lead to poorer cognitive aging.