Dementia Risk in Nonagenarians: Insights from LifeAfter90 Study

Reaching age 90 does not necessarily mean escaping dementia, according to research conducted by the University of California, Davis Health and Kaiser Permanente. This study, part of the ongoing LifeAfter90 project, involved tracking more than 800 adults aged 90 and above. The researchers discovered that dementia risk persists well into advanced age, showing differences linked to sex, race, ethnicity, and genetics. The findings are published in The Lancet Healthy Longevity.

Understanding Dementia Risk After 90

Rachel Whitmer, a UC Davis Health professor, highlighted the importance of this study in understanding who gets affected by dementia after 90 and the role of the Alzheimer’s risk gene, APOE. Unlike studies focused on those over 65, this research involved a diverse group of participants who had no dementia indications at the outset.

The participants were Kaiser Permanente members, assessed biannually for cognitive health changes. Given their long-term enrollment, historical health records dating back to the 1960s were available for analysis.

Key Findings

The study’s results revealed significant findings:

• Women had twice the risk of developing dementia compared to men after 90.
• Black participants experienced a 75% higher dementia risk than Asian participants, with Black and Hispanic participants having higher rates overall compared to White and Asian participants.

“It is striking that racial and ethnic disparities in dementia risk observed in younger adults continue into the 10th decade of life,” stated Hilary Colbeth, the study’s first author.

Role of APOE Gene

The study examined the APOE gene, associated with Alzheimer’s disease. While the APOE2 variant offers protection, the APOE4 variant links to increased Alzheimer’s risk. In most study participants, APOE4 did not raise dementia incidence significantly. However, in specific groups, it was linked to higher risk, especially doubling the risk among Black participants.

Colbeth noted the differing impacts of APOE4 on males and females, prompting further investigation into APOE’s effects on mortality among those over 90.

Despite some participants having risk factors like hypertension or carrying APOE4, they remained cognitively healthy. Understanding this protection is now a primary focus.

Implications for Aging and Dementia

Lisa George, a New York City-based psychiatric expert not involved in the study, emphasized that reaching 90 without dementia does not eliminate future risk. She pointed out that age remains a significant dementia risk factor, but individuals can develop dementia beyond their nineties.

George highlighted the complexity of dementia in the oldest adults, where various processes affect the brain simultaneously. Memory issues in older adults should not be automatically presumed as dementia, as other conditions like anxiety or medication effects can mimic it.

Future Research Directions

The findings underscore the need for research focused on individuals over 90, a rapidly growing demographic. Future studies may aid in devising strategies for early detection and prevention. New biomarker tests for Alzheimer’s could identify risks well before symptoms appear, guiding prevention trials.

The LifeAfter90 study provides crucial insights, potentially shaping screening, treatment, and prevention approaches for the aging population.