Key result
African American race was associated with higher rates of rapid (7% vs 5%) and moderate (20% vs 15%) cognitive decline compared to European Americans, alongside higher rates of incident dementia.
Why the study?
The APOEɛ4 allele association with incident Alzheimer's dementia is higher among European Americans than African Americans but similar for cognitive decline rates, prompting examination of racial differences in these associations.
Does the APOEɛ4 allele differentially affect cognitive decline and incident Alzheimer's dementia in African Americans compared to European Americans?
Cohort (n=5,117)
Does the APOEɛ4 allele differentially affect cognitive decline and incident Alzheimer's dementia in African Americans compared to European Americans?
African Americans have lower baseline cognitive levels, leading to a higher likelihood of meeting the threshold for Alzheimer's dementia even with mild or slow decline, which explains the attenuated association of the APOEɛ4 allele with incident dementia in this group.
May warrant closer cognitive monitoring in African Americans; leaves open modifiable factors and targeted interventions.
BACKGROUND: The association of the APOEɛ4 allele with incident Alzheimer's dementia is higher among European Americans (EAs) than African Americans (AAs), but similar for the rate of cognitive decline. OBJECTIVE: To examine the racial differences in the association of the APOEɛ4 allele with incident Alzheimer's dementia and cognitive decline. METHODS: Using a population-based sample of 5,117 older adults (66% AAs and 63% females), we identified cognitive trajectory groups from a latent class mixed model and examined the association of the APOEɛ4 allele with these groups. RESULTS: The frequency of the APOEɛ4 allele was higher among AAs than EAs (37% versus 26%). Four cognitive trajectories were identified: slow, mild, moderate, and rapid. Overall, AAs had a lower baseline global cognition than EAs, and a higher proportion had rapid (7% versus 5%) and moderate (20% versus 15%) decline, but similar mild (44% versus 46%), and lesser slow (29% versus 34%) decline compared to EAs. Additionally, 25% of AAs (13% of EAs) with mild and 5% (<1% of EAs) with slow decline were diagnosed with incident Alzheimer's dementia. The APOEɛ4 allele was associated with higher odds of rapid and moderate decline compared to slow decline among AAs and EAs, but not with mild decline. CONCLUSIONS: AAs had lower cognitive levels and were more likely to meet the cognitive threshold for Alzheimer's dementia among mild and slow decliners, explaining the attenuated association of the ɛ4 allele with incident Alzheimer's dementia among AAs.
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Rajan et al. (2019) conducted a cohort in Alzheimer's dementia and cognitive decline (n=5,117). African American race and APOEɛ4 allele vs. European American race and absence of APOEɛ4 allele was evaluated on Incident Alzheimer's dementia and cognitive decline trajectories. African American race was associated with higher rates of rapid (7% vs 5%) and moderate (20% vs 15%) cognitive decline compared to European Americans, alongside higher rates of incident dementia.
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