People who reach their 90s without dementia might appear to have escaped much of the danger of cognitive decline. Until recently, however, scientists had relatively little evidence showing what happens to dementia risk at such advanced ages.
That gap is becoming increasingly important as lifespans rise around the world. By 2100, roughly 230 million people 90 or older could be alive worldwide, increasing the need for better information about how the brain ages in this rapidly growing population.
Researchers at UC Davis Health and Kaiser Permanente are helping address that question through the LifeAfter90 study, which has followed a large group of adults in their 90s since 2018. The latest findings, published in The Lancet Healthy Longevity, show notable differences in dementia risk by sex, race, ethnicity, and genetics.
"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."
