Study Reveals Dementia Risk Factors in Individuals Over 90

As lifespans increase globally, understanding dementia risk in the elderly becomes crucial. A recent study conducted by researchers at UC Davis Health and Kaiser Permanente sheds light on this issue, particularly focusing on individuals who reach their 90s without dementia. The findings, published in The Lancet Healthy Longevity, reveal that dementia risk is significantly influenced by factors such as sex, race, ethnicity, and genetics.

The LifeAfter90 study has been tracking a diverse cohort of adults aged 90 and older since 2018. Under the leadership of Rachel Whitmer, a professor of public health sciences and neurology at UC Davis Health, the study has gathered extensive medical data from participants, many of whom have records dating back to the 1960s. This research is particularly noteworthy as it represents the first comprehensive analysis of dementia risk in a highly diverse group of older adults.

The results indicate that the disparities in dementia risk observed in younger populations persist into advanced age. Women aged 90 and older are found to have approximately double the risk of developing dementia compared to men. Additionally, racial and ethnic differences are pronounced, with black participants facing a 75% higher risk of dementia compared to their Asian counterparts. Hilary Colbeth, a postdoctoral scholar at UC Davis and the study's first author, noted that these disparities highlight the need for targeted awareness and intervention strategies.

The study also examined the role of the APOE gene, which is closely associated with Alzheimer's disease. Variants of this gene can have opposing effects on dementia risk. For instance, the APOE2 variant is linked to a reduced likelihood of developing Alzheimer's, while the APOE4 variant is associated with increased risk. Interestingly, the protective effect of APOE2 remains significant even beyond the age of 90, with carriers showing a 60% lower risk of dementia. Conversely, the impact of APOE4 varies; while it does not significantly elevate dementia risk across the entire study population, it appears to double the risk among black participants and is associated with higher risk in men.

An intriguing aspect of the research is the observation that some participants, despite having established risk factors such as hypertension and high cholesterol, maintained cognitive health into their 90s. This raises questions about the biological or environmental factors that may confer protection against dementia. Understanding these mechanisms could provide valuable insights into potential strategies for dementia prevention.

The study underscores the importance of recognizing that reaching 90 without dementia does not guarantee immunity from future cognitive decline. As Rachel Whitmer emphasizes, it is essential for healthcare providers to be aware of the varying risks among different demographic groups, ensuring that discussions about dementia risk and prevention are inclusive and informed. This research was supported by the National Institute on Aging of the National Institutes of Health.