More years of periods and hormone therapy tied to healthier brain vessels

Older women who had more years between their first period and menopause, and women who had used hormone therapy around menopause, showed fewer signs of damage to the brain’s smallest blood vessels, a Swedish-led study reports.¹ The study, published on 4 November 2026 in the journal Neurology, followed 352 women from Gothenburg who were 70 years old and had no problems with memory or thinking when it began.¹ The researchers stress that they found a link, not proof that hormones caused the difference.²

What the researchers did

The team, led by researchers at Karolinska Institutet in Sweden, scanned each woman’s brain with MRI (magnetic resonance imaging, a scanner that uses magnets to take detailed pictures) at age 70 and again five years later.¹ They also had information on when each woman had her first period, when her menopause began, and whether she had used the contraceptive pill or menopause hormone therapy.¹

They called the time between the first period and menopause, or surgery to remove the ovaries, the “reproductive period.” On average it lasted 37 years.² This span is often used as a rough measure of how long a woman’s body made its own estrogen.³

On the scans, the researchers looked for four signs of cerebral small vessel disease, meaning damage to the brain’s tiniest blood vessels: bright spots in the brain’s wiring (called white matter hyperintensities), tiny bleeds, small holes left by old blockages (lacunes), and widened fluid spaces around blood vessels.² Each woman scored from zero to four, depending on how many signs were found.² This kind of vessel damage is associated with stroke, memory and thinking problems, and dementia.²

The team also measured the fine structure of the white matter, the brain’s wiring, and the thickness of the brain’s outer layer in areas vulnerable to Alzheimer’s disease.¹ The release does not describe results for that outer-layer measure.

What the numbers show

After the researchers accounted for education, number of pregnancies and total time spent breastfeeding, a longer reproductive period was linked to 8% lower odds of having at least two signs of small-vessel damage.²

Hormone use was common in this group. About 73% of the women had ever used birth control pills, and 61% had used or were using menopause hormone therapy.² After adjusting for factors including high blood pressure and heart disease, women who had used hormone therapy had 59% lower odds of a heavier burden of small-vessel damage, according to a News-Medical report summarized by UA.NEWS.² They also had tiny bleeds and widened fluid spaces less often.²

Use of hormone therapy during menopause was also tied to a healthier-looking structure in the white matter.¹ The UA.NEWS summary describes this as an early sign of healthier brain tissue and says birth control pill use showed the same link.²

Women who had used both the pill during their reproductive years and hormone therapy at menopause had the most favorable picture of blood vessel health in the brain.¹

“Our results suggest that hormonal exposure across different periods of a woman’s life may have cumulative effects also on the cerebrovascular health in later life. The findings suggest that the brain’s blood vessels may play an important role in the link between oestrogen and brain ageing.”

That is how Anna Marseglia, an assistant professor at Karolinska Institutet and the study’s senior author, described the results.¹

What it does not show

This is an observational study. The researchers watched what happened in a group of women; they did not give anyone hormones and compare them with women who got none. So it cannot show whether hormones or a longer reproductive span caused the healthier vessels. Women who use hormone therapy may differ from those who do not in other ways that also affect blood vessels.

The study’s first author was direct about this.

“Furthermore, the study is an observational study, and we cannot therefore determine cause and effect. The results cannot therefore be used as a basis for recommending hormone therapy for preventive purposes”

That was said by Giulia Lorenzon, a researcher at Yale University and former postdoctoral researcher at Karolinska Institutet.¹

There are other limits. The women reported their own hormone use, so they may have misremembered details.² The team lacked information on when treatment started, the dose and the type of treatment.¹ They also did not track hormone levels through the women’s lives.²

The study also measured signs on brain scans. It did not report whether the women with fewer vessel changes went on to have fewer strokes or less dementia. And all 352 women came from one Swedish city, so the results may not apply to every group of women.¹

Who did the study and who paid for it

Researchers from Karolinska Institutet, Yale University, the University of Gothenburg, Harvard Medical School and several other universities worked on the study.¹ It was funded by groups including the Swedish Research Council, Forte, the Centre for Innovative Medicine, the Dementia Foundation, the Alzheimer’s Foundation and Karolinska Institutet.¹ The researchers state that they have no conflicts of interest.¹ The sources do not name any drug company as a funder.

How it fits with other research

Women are more likely than men to develop Alzheimer’s disease, and the researchers note that this difference may be partly related to changes in estrogen across life.¹ Their new results point to blood vessels as one possible part of that story.¹

Other research does not line up neatly. Earlier studies on reproductive span and thinking found inconsistent results, and studies of hormone therapy and thinking have also clashed.³ In April 2026, a study of more than 14,000 women in the US Nurses’ Health Study, published in the journal Menopause, linked a longer reproductive span to better upkeep of memory and thinking.³ But in that study, hormone therapy started within 10 years of menopause showed no benefit for thinking.³

Commenting on that US study, Stephanie Faubion, medical director for The Menopause Society, said the results supported current guidelines that recommend against using hormone therapy to prevent dementia.³

The two studies measured different things. The Swedish study looked at signs of vessel damage on brain scans, while the US study tracked scores on memory and thinking tests over time.¹³ A link between hormone therapy and scan signs does not show that hormone therapy changes how well people think or remember.

What to watch next

The key open question is cause and effect. Only studies that assign women to hormone therapy or no treatment, and follow them long enough, can test whether hormones themselves protect small brain vessels. Better records of when treatment began, the dose and the type would also help, since this study lacked them.¹

It will also matter whether the vessel signs seen at 70 and 75 go on to predict stroke or dementia in these same women, and whether the Swedish findings hold up in other countries and in more varied groups of women.