Early menopause could be a warning sign for future age-related brain decline, a new study says.

Women who entered menopause before 40 had a greater cognitive decline than women who entered menopause after 50, according to a study published recently in the journal Alzheimer’s & Dementia.

Early menopause also was associated with worse depression, researchers said.

"Understanding this relationship in-depth could potentially help us design treatments that delay the onset of dementia in at-risk patients," lead researcher Miharu Nakanishi, an associate professor at Tohoku University Graduate School of Medicine in Japan, said in a news release.

For the study, researchers analyzed data from a long-term U.K. study of aging, tracking the health of more than 4,700 women and nearly 4,300 men.

Women who entered menopause early tended to experience a more dramatic decline in their thinking and memory skills than those whose menopause occurred in middle-age, results show.

This link remained even after researchers accounted for the potential effect of depression on the women’s brain health.

"When looking for associations, we want to rule out as many other modifiable risk factors for dementia as possible," Nakanishi said. 

“Since early menopause increases the risk of depression, which then increases the risk of dementia, we had to control for this factor to determine if early menopause in of itself was a direct risk factor,” Nakanishi added.

On the other hand, women who entered menopause at the more usual time of life wound up with better cognitive function than men of the same age, researchers found.

Hormone replacement therapy used to treat menopause symptoms had no effect one way or the other on women’s brain health, results showed.

“The results imply that women who experience early menopause may constitute a sex-specific high-risk group for cognitive decline that may not be necessarily attributed to depressive symptoms compounded by menopause,” researchers concluded in their paper.

However, more research is needed to understand why early menopause might affect women’s brain health, the team noted.