In the Oldest Old, Dementia Risk Still Tracks Sex, Race and Genetics
A study of people over 90 found women and Black participants faced notably higher risk, challenging the assumption that risk factors flatten with extreme age.
A study of people over 90 found that dementia risk remains strongly shaped by sex, race and genetics, with women and Black participants facing notably higher risks.
Why studying the oldest old is difficult and valuable
Research on people beyond 90 is scarce for practical reasons: the cohort is small, difficult to recruit, and shrinking during any study period.
It is also where a specific assumption gets tested. Risk factors identified in younger populations are often assumed to converge at extreme age — the reasoning being that anyone who reaches 90 has already survived the conditions that kill most people, leaving a population selected for resilience.
This study finds the assumption does not hold for dementia. The differentials persist.
What "race" is measuring here
This is the part most easily misread. Race in epidemiological research is not a biological category. It functions as a marker for an accumulated set of exposures:
- Differences in access to healthcare across a lifetime.
- Cardiovascular risk factors — hypertension and diabetes prominently — which are themselves strongly linked to dementia risk.
- Educational and occupational differences affecting cognitive reserve.
- The physiological effects of chronic stress associated with discrimination.
A finding that Black participants face higher risk is therefore evidence about the cumulative effect of unequal exposures, not about inherent difference. Reading it the other way inverts the meaning of the result.
The sex differential
Women's higher dementia risk is well established and not fully explained. Longer average lifespan accounts for part of it — dementia risk rises steeply with age — but studies controlling for age still find a differential, suggesting hormonal, genetic or social contributions that remain under investigation.
Why it matters practically
Populations over 90 are the fastest-growing age group in many countries. Understanding what drives dementia risk in this cohort specifically determines where prevention and care resources should go.
If risk factors persist rather than flattening, interventions targeting them retain value at ages where they are frequently assumed to have none — which is a direct argument against the therapeutic pessimism that often attaches to very old patients.