Episodic Memory and Executive Function Are Differentially Affected by Retests but Similarly Affected by Age in a Longitudinal Study of Normally-Aging Older Adults

Abstract

Episodic memory and executive function are two cognitive domains that have been studied extensively in older adults and have been shown to decline in normally-aging older individuals. However, one of the problems with characterizing cognitive changes in longitudinal studies has been separating effects attributable to normal aging from effects created by repeated testing or practice. In the present study, 166 people aged 65 and older were enrolled over several years and tested at least 3 times at variable intervals (M = 3.2 yrs). The cognitive measures were composite scores. Each composite was made up of five neuropsychological tests, previously identified through factor analysis. For one pair of composite scores, variance attributable to age was removed from each subtest through regression analyses before z-scores were computed, creating two age-corrected composites. A second pair of composites were not age-corrected. Using linear mixed-effects models, we first explored retest effects for each cognitive domain, independent of age, using the age-corrected composites. We then modeled aging effects using the age-uncorrected composites after subtracting out retest effects. Results indicated significant retest effects for memory but not for executive function, such that memory performance improved across the three testing sessions. When these practice effects were removed from the age-uncorrected data, effects of aging were evident for both executive and memory function with significant declines over time. We also explored several individual difference variables including sex, IQ, and age at the initial testing session and across time. Although sex and IQ affected performance on both cognitive factors at the initial test, neither was related to practice effects, although young-older adults tended to benefit from practice to a greater extent than old-older adults. In addition, people with higher IQs showed slower age-related declines in memory, but no advantages in executive function. These findings suggest that (a) aging affects both memory and executive function similarly, (b) higher IQ, possibly reflecting cognitive reserve, may slow age-related declines in memory, and (c) practice through repeated testing enhances performance in memory particularly in younger-older adults, and may therefore mask aging effects if not taken into account.

Grip strength, gait speed, and trajectories of cognitive function in community‐dwelling older adults: A prospective study

“…This is possibly a limitation of the cognitive tests used for these two domains (COWAT and HVLT‐R delayed recall), which arises from practice after repetitive assessments. Indeed, learning effects have been previously observed in both tests 29–31 . This suggests that it may be necessary to regularly change the letter used for COWAT or the word list of HVLT‐R to mitigate against learning effects, especially for a cohort of relatively healthy individuals.…”

“…Indeed, learning effects have been previously observed in both tests. 29 , 30 , 31 This suggests that it may be necessary to regularly change the letter used for COWAT or the word list of HVLT‐R to mitigate against learning effects, especially for a cohort of relatively healthy individuals. On the other hand, it is also plausible that individuals with high cognitive function were able to accumulate vocabulary over time or familiarize a certain list of words, and subsequently generate personalized strategies to retrieve words from their vocabulary storage and memory.…”

Misinterpreting cognitive change over multiple timepoints: When practice effects meet age-related decline.

“…However, the precise magnitude of PEs (e.g., exact percent change in MCI status) is not generalizable from one sample to another. PEs will almost always vary based on age or other demographic characteristics, the specific cognitive measures, and the different retest intervals across studies (Glisky et al, 2022; Kremen et al, 2022). Given this heterogeneity in PE magnitudes, we discourage the generalization of PEs based on research studies.…”

Protective roles of meditation practice and self‐esteem on cognitive functions over time: findings from the Midlife in the United States study

“…4 Episodic memory and executive function are two major cognitive domains that have been studied extensively. 1 Episodic memory includes individuals' recollections of personal experiences specific to time and place; evidence supports that episodic memory may decline throughout life. 2 In comparison, executive functions consist of cognitive abilities such as planning, organizing, reasoning, and problem-solving; many of these abilities are also associated with age-related cognitive decline.…”

“…Cognitive performance declines with age in adulthood 1–3 ; specific areas of decline include concentration, attention and processing speed, visual and verbal memory, language, executive function, and spatial and/or psychomotor ability 4 . Episodic memory and executive function are two major cognitive domains that have been studied extensively 1 .…”