Plate Nº 15 · recorded October 10, 2026
Health & Medicine ResearchReported finding
Women Over 90 Face Twice the Dementia Risk of Men, Study Finds
Women over 90 have about twice the dementia risk of men, and Black participants face 75% higher risk than Asian participants, a study of 800+ adults shows.
By James Calloway4 min read750 words
In brief
- Women aged 90+ had about twice the dementia risk of men in the LifeAfter90 study.
- Black participants faced a 75% higher dementia risk than Asian participants.
- The protective gene variant APOE2 cut dementia risk by 60% even after age 90.
- The study followed more than 800 Kaiser Permanente members with a median age of 92.
- Findings were published in The Lancet Healthy Longevity on September 1, 2026.
Women aged 90 and older have about twice the dementia risk of men, according to a new study of more than 800 adults published in The Lancet Healthy Longevity on September 1, 2026. The research also found that Black participants faced a 75% higher risk than Asian participants, showing that dementia disparities established earlier in life persist deep into the tenth decade.
The LifeAfter90 study, run by researchers at UC Davis Health and Kaiser Permanente, has followed adults in their 90s since 2018. It is the first study of dementia after age 90 conducted in a highly diverse cohort. Participants had a median age of 92 and showed no signs of dementia when they enrolled. Researchers evaluate them every six months to track changes in cognitive health.
"We know from other studies, done in people 65 and older, that there are differences in dementia rates, and women tend to have higher risk, but nobody knew if that was true after 90," said Rachel Whitmer, UC Davis Health professor of public health sciences and neurology, chief of epidemiology and senior author on the study. "We need to understand who is most affected by dementia after 90 and how the main Alzheimer's risk gene (APOE) factors in."
Why does dementia after 90 matter now?
Scientists have long had little evidence about dementia risk at such advanced ages. That gap matters because lifespans keep rising worldwide. By 2100, roughly 230 million people aged 90 or older could be alive globally, and clinicians will need far better information about how the brain ages in this rapidly growing group.
The study's participants are Kaiser Permanente members, and their long history with the health system gives researchers access to an unusually rich medical record. For some participants, records stretch back to the 1960s.
Which groups carry the highest risk?
The analysis revealed that disparities seen in younger adults continue into extreme old age:
- Women 90 and older had roughly double the dementia risk of men.
- Black participants faced a 75% higher risk than Asian participants.
- Black and Hispanic participants had significantly higher dementia incidence rates than white and Asian participants.
"It is striking that the racial and ethnic disparities in dementia risk observed in younger adults continue into the tenth decade of life," said Hilary Colbeth, a UC Davis postdoctoral scholar in public health sciences and first author on the paper. "Specifically, black and Hispanic participants had significantly higher dementia incidence rates than white and Asian participants."
How do Alzheimer's risk genes behave after 90?
The researchers examined APOE, a gene strongly associated with Alzheimer's disease. Different versions of it can push risk in opposite directions. APOE2 is considered protective and linked to a lower likelihood of developing Alzheimer's, while APOE4 raises risk.
The protective effect of APOE2 held strong even beyond age 90. Participants carrying that variant had a 60% lower risk of dementia.
APOE4 told a more complicated story. Across the whole study population, the variant did not substantially increase dementia incidence. Within specific groups, though, it mattered. APOE4 was associated with higher risk among men, and among Black participants it approximately doubled dementia risk.
"We saw evidence that APOE4 impacts males and females differently after age 90," Colbeth said. "This has prompted us to look more closely at how APOE genotypes impact mortality among those with and without dementia by age 90."
Why did some high-risk people stay healthy?
The findings also surfaced a puzzle. Some participants had well-established dementia risk factors, including hypertension and high cholesterol, during their 60s and 70s, yet remained cognitively healthy decades later. Some APOE4 carriers also reached their 90s without developing dementia.
Researchers now want to find out what protected these individuals. Understanding those biological or environmental mechanisms could eventually reveal ways to reproduce the same protective effects in other people. For now, that remains an open question, and the study does not establish what shielded them.
Even so, the results already give doctors a clearer picture of how dementia risk operates in extreme old age and could support more informed clinical care.
"Doctors need to know that certain groups are at higher or lower risk," Whitmer said. "We can't just assume that someone from a high-risk group makes it to 90 without dementia and they're in the clear. We need to talk about risk reduction for everyone."
The National Institute on Aging of the National Institutes of Health supported the research under grants R01AG056519 and P30AG072972.
via rachelwhitmer.ucdavis.edu (Original)
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