Observational study finds women twice as likely as men to develop dementia — Evidence Review
Published in The Lancet Healthy Longevity, by researchers from UC Davis Health, Kaiser Permanente
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Table of Contents
Reaching age 90 without dementia does not eliminate risk—new research finds that sex, race, ethnicity, and genetics continue to influence dementia incidence in this age group. Related studies largely support these findings, confirming persistent disparities and elevated risk for women and certain minority groups; see the original study from UC Davis Health for details.
- Multiple studies consistently report that women face higher risk and incidence of dementia than men, particularly at advanced ages, which aligns with the new findings 1 2 5 6 11.
- Racial and ethnic disparities in dementia prevalence and incidence are well-documented, with Black and Hispanic individuals experiencing greater risk than white and Asian populations; the new study’s observation of persistent disparities after age 90 is consistent with prior literature 1 8.
- Genetic factors, particularly variants of the APOE gene, remain significant contributors to dementia risk, but their impact can differ by sex and ethnicity—recent studies highlight the importance of examining these interactions in diverse cohorts 4 11.
Study Overview and Key Findings
Understanding dementia risk in the oldest-old is increasingly urgent as global life expectancy rises and the population aged 90 and above expands rapidly. Most dementia research has focused on younger elderly populations, often lacking racial, ethnic, and genetic diversity, which limits understanding of risk factors in the oldest-old. This new study addresses these gaps by closely following a diverse cohort of individuals aged 90+ with comprehensive health records, offering insights into how longstanding disparities and genetic risks persist or evolve in advanced age.
| Property | Value |
|---|---|
| Study Year | 2026 |
| Organization | UC Davis Health, Kaiser Permanente |
| Journal Name | The Lancet Healthy Longevity |
| Authors | Hilary L Colbeth, Maria M Corrada, Dan Mungas, Paola Gilsanz, Kristen M George, Reham Gaied, Claudia H Kawas, Charles DeCarli, Rachel A Whitmer |
| Population | Diverse group of older adults aged 90 and above |
| Sample Size | n=800 |
| Methods | Observational Study |
| Outcome | Dementia incidence, association with APOE genotype, race, and sex |
| Results | Women were twice as likely as men to develop dementia. |
The LifeAfter90 study, initiated in 2018, followed Kaiser Permanente members aged 90 and older who were dementia-free at enrollment. Through biannual cognitive assessments, researchers tracked new dementia cases and leveraged extensive health records—some dating back to the 1960s—to assess how factors like sex, race, ethnicity, and APOE genetic variants influence dementia risk in advanced age. Key findings include:
- Women were twice as likely as men to develop dementia after age 90, mirroring patterns seen in younger populations.
- Black participants had a 75% higher risk of dementia than Asian participants; Black and Hispanic individuals experienced significantly higher incidence than white and Asian counterparts.
- The APOE2 allele was strongly protective, while the effect of APOE4 varied by sex and ethnicity, notably increasing risk among men and Black participants.
- Some individuals with established risk factors (e.g., hypertension, high cholesterol, APOE4) remained cognitively healthy into their 90s, highlighting the need to investigate resilience mechanisms.
Literature Review: Related Studies
To contextualize these findings, we searched the Consensus database (over 200 million research papers) using the following queries:
- dementia prevalence gender differences
- age 90 dementia risk factors
- women men dementia comparison studies
Related Studies: Thematic Overview
| Topic | Key Findings |
|---|---|
| How do sex and gender influence dementia risk and progression, especially after age 90? | - Women consistently show higher prevalence and incidence of dementia and Alzheimer's disease, with risk divergence becoming more pronounced after age 85 1 2 5 6 11. - Faster cognitive decline in women may contribute to higher late-life dementia risk, despite initially greater cognitive reserve 2 11. |
| What is the impact of racial, ethnic, and regional differences on dementia risk? | - Dementia rates are higher in Europe and North America, with Black and Hispanic populations facing greater risk than white and Asian groups 1 8. - Disparities persist into advanced age, and population-attributable fractions for modifiable risk factors are higher in low- and middle-income countries 8. |
| Which genetic and modifiable factors contribute to dementia risk in the oldest-old? | - APOE4 increases risk, especially for women and Black individuals, while APOE2 is protective even after age 90 4 11. - Modifiable risk factors (e.g., hypertension, physical inactivity, obesity, social engagement) remain important, with some having cumulative effects into late life 7 8 9 10. |
| Are dementia incidence and prevalence changing over time, and what explains these trends? | - Incidence rates have declined in Europe and North America by about 13% per decade, with more pronounced declines in men 3. - Improvements in education, cardiovascular health, and population health may contribute to these trends, but differences remain across regions and demographic groups 3 8. |
### How do sex and gender influence dementia risk and progression, especially after age 90?
The new study’s finding that women are twice as likely as men to develop dementia after age 90 is consistent with a longstanding body of research indicating higher dementia prevalence and incidence in women, particularly in advanced age groups. Related studies suggest this may be due to a combination of biological, genetic, and resilience factors, including differences in cognitive reserve and rates of cognitive decline.
- Meta-analyses and cohort studies confirm that dementia and Alzheimer’s rates are higher in women, with the divergence occurring most markedly after age 85 1 5 6.
- Women tend to have higher baseline cognitive performance but experience faster cognitive decline in late life, potentially explaining the greater risk of late-life dementia 2 11.
- Sex differences in risk factors, genetics (notably APOE4), and resilience mechanisms contribute to disparities in both incidence and progression 4 11.
- The new study’s finding that sex differences persist even after age 90 reinforces the need to consider gender in dementia risk assessment 1 2 5 6 11.
### What is the impact of racial, ethnic, and regional differences on dementia risk?
Persistent disparities by race and ethnicity, as reported in the new study, are widely documented across dementia research. Black and Hispanic individuals are at higher risk compared to white and Asian populations, and these disparities extend into the oldest-old age group. Regional differences, such as higher rates in Europe and North America, further highlight the influence of socioeconomic and environmental factors.
- Systematic reviews and meta-analyses show greater dementia prevalence in Black and Hispanic populations, with similar findings regarding higher risk in high-income regions 1 8.
- Disparities are linked to differences in modifiable risk factors, healthcare access, and social determinants of health 8.
- Population-attributable fractions for dementia risk factors are higher in low- and middle-income countries, indicating a greater potential for prevention if resources are available 8.
- The persistence of disparities after age 90, as observed in the new study, emphasizes the importance of inclusive research and risk reduction strategies 1 8.
### Which genetic and modifiable factors contribute to dementia risk in the oldest-old?
Both genetic and modifiable risk factors remain important contributors to dementia risk in the oldest-old. The LifeAfter90 study’s findings regarding APOE allele effects and the continued significance of midlife health factors are echoed in prior research, which also points to the protective benefits of social engagement and healthy lifestyle choices late in life.
- APOE4 is a well-established risk factor, with its impact varying by sex and ethnicity; APOE2 offers protective effects that persist into advanced age 4 11.
- Midlife hypertension, obesity, depression, and diabetes are among the strongest modifiable risk factors for dementia, with their influence measurable even decades later 7 8 10.
- Social and mental activity, antioxidant supplement use, and caffeine intake are associated with reduced dementia risk among the oldest-old 9.
- The persistence of risk among those with established genetic or health risk factors, as noted in the new study, highlights the need to understand resilience mechanisms 7 9 10.
### Are dementia incidence and prevalence changing over time, and what explains these trends?
Long-term data indicate that dementia incidence has declined in high-income regions over recent decades, a trend attributed to improvements in education, cardiovascular health, and life-course socioeconomic factors. However, these trends are not uniform across all populations, and disparities persist.
- Incidence rates declined by about 13% per decade in Europe and North America, with a more pronounced decrease in men 3.
- Changes in modifiable risk factor profiles, such as increased education and improved vascular health, may partly explain these trends 3 8.
- Despite overall declines, disparities by sex, ethnicity, and region remain, underscoring the importance of targeted prevention efforts 1 3 8.
- The new study highlights that, while overall risk may change, certain groups remain at elevated risk even in advanced age 3 8.
Future Research Questions
Further research is needed to clarify the mechanisms underlying resilience to dementia in the oldest-old, to disentangle the complex interplay between genetics and environmental factors, and to develop more effective, equitable risk reduction strategies for diverse aging populations.
| Research Question | Relevance |
|---|---|
| What biological or lifestyle factors confer resilience to dementia in individuals aged 90 and above? | Identifying protective factors could inform prevention strategies and help explain why some high-risk individuals remain cognitively healthy late in life 7 9. |
| How do APOE genotypes interact with sex and ethnicity to affect dementia risk after age 90? | Clarifying these interactions could improve risk prediction and guide personalized interventions, as genetic effects appear to vary by both sex and ethnicity 4 11. |
| What are the most effective late-life interventions for reducing dementia risk in the oldest-old? | Evidence is limited on which interventions retain efficacy in very advanced age, and whether strategies effective in younger elderly populations also benefit those aged 90+ 7 8 9. |
| How do social and environmental factors contribute to racial and ethnic disparities in dementia risk after age 90? | Understanding these contributions is essential for developing equitable risk reduction policies and addressing persistent disparities in dementia incidence 1 8. |
| What factors explain the observed decline in dementia incidence over the past decades and does this trend extend to all groups? | Investigating the drivers of incidence trends can help sustain declines and ensure all demographic groups benefit equally from advances in public health and prevention 3 8. |