Forgetting Changes Little in Healthy Older People
It is commonplace in the research and medical communities to attempt to distinguish normal aging from pathological aging. This seems problematic, as it is all aging under the hood. A healthy older person is still impacted by the mechanisms of aging, a burden of molecular damage and its consequences, just less impacted than a similarly aged peer suffering evident age-related diseases. The pace of aging, and which forms of damage build upon one another to the point of runaway dysfunction and pathology, varies considerably from individual to individual. Nonetheless, there is still the drive to attempt to distinguish normal aging from pathological aging, particularly when it comes to cognitive function.
Aging is typically associated with declines in episodic memory, executive functions, and sleep quality. Therefore, the sleep-dependent stabilization of episodic memory is suspected to decline during aging. This might reflect in accelerated long-term forgetting, which refers to normal learning and retention over hours, yet an abnormal retention over nights and days. Accelerated long-term forgetting has been observed in dementia, mild cognitive impairment, and in people with memory complaints.
Here, we explored whether accelerated long-term forgetting also manifests in healthy aging. We investigated verbal episodic memory in 236 healthy men and women between 18 and 77 years of age. All participants were mentally intact in terms of executive functions, working memory, episodic memory, verbal intelligence, and mood. We related their forgetting rates over one week following learning to their subjective sleep quality and executive functions. Fifteen words were freely recalled and then recognized among 30 distractor words at 30 minutes and again at one week following learning. Although the healthy older adults compared to the healthy younger adults reported a diminished sleep efficiency and learned fewer words, they exhibited no disproportionate forgetting over days.
Hence, accelerated long-term forgetting is not present in healthy aging but might be a first sign of memory dysfunction due to neuropathology.