Scientists Followed 800 Adults Over 90. One Group Had Double Dementia Risk

A groundbreaking study tracking over 800 adults aged 90 and older has revealed that dementia risk persists well into the oldest age brackets, challenging common assumptions about dementia's link to aging. Researchers from the University of California, Davis Health and Kaiser Permanente analyzed data from the LifeAfter90 study, which enrolled participants who had no signs of dementia upon joining.

The findings, published in The Lancet Healthy Longevity, showed that dementia risk varies significantly based on sex, race, ethnicity, and genetics. While women generally face a higher dementia risk, the study found that Black and Hispanic individuals had notably higher incidence rates compared to white and Asian participants. Crucially, the study uncovered that the APOE gene, long associated with Alzheimer's risk, continued to protect against dementia even after age 90, reducing incidence by roughly 60 percent in carriers of the protective APOE2 variant.

However, the impact of APOE4, a risk gene, differed by sex and race - increasing dementia risk among men and nearly doubling it among Black participants. The researchers also noted that some individuals remained cognitively healthy despite carrying risk factors like hypertension or high cholesterol, while others avoided dementia despite carrying the APOE4 gene.

This highlights the complex interplay of aging processes and genetic factors in cognitive decline. Experts caution that dementia remains a significant concern even in the oldest-old, and that age alone is not a guarantee against the condition. The study underscores the need for tailored risk assessments and preventive strategies across diverse populations as the global elderly population continues to grow.