Past and Future Episodic Detail Retrieval Is Reduced Among Clinically Normal Older Adults at Higher Genetic Risk for Late-Onset Alzheimer's Disease

Objective: Remembering and imagining personal events that are rich in episodic (i.e., event-specific) detail is compromised in older adults who have mild cognitive impairment, a known risk factor for Alzheimer's disease dementia. Less clear is whether lower episodic detail generation is associated with higher risk for Alzheimer's disease dementia before mild clinical decline is detectable. Method: We compared past and future autobiographical thinking in clinically normal older adult carriers of the Alzheimer's disease-associated apolipoprotein E e4 allele (APOE4; n = 39) to demographically and neuropsychologically similar non-APOE4 carriers (n = 43). Results: APOE4 carriers showed a significant reduction for episodic details when remembering past events (d = .47) and imagining future events (d = .46), but not for nonepisodic details. Conclusions: These findings suggest that APOE4 is associated with a selective reduction of episodic detail during past and future autobiographical thinking among clinically normal older adults. Reduced episodic detail generation, therefore, may be an early cognitive associate of higher risk for Alzheimer's disease dementia. Key Points Question: Is lower episodic detail generation while imagining future events associated with higher risk for Alzheimer's disease dementia before mild clinical decline is detectable? Findings: Clinically normal older adult APOE4 carriers not only showed a reduction in episodic detail generation while remembering past events, but also while imagining future events, relative to APOE4 noncarriers. Importance: Our findings suggest that reduced episodic detail generation is associated with higher risk for Alzheimer's disease dementia in clinically normal older adults. Next Steps: Future research could investigate the neural mechanisms behind this Alzheimer's risk-related selective reduction in episodic detail generation, in particular in relationship to race, ethnicity, and APOE4.