Predictors of Retest Effects in a Longitudinal Study of Cognitive Aging in a Diverse Community-Based Sample

Impact of Age on Cognitive Testing Practice Effects and Cardiorespiratory Responses

Objective: This study tested the hypothesis that healthy aging attenuates cognitive practice effects and, consequently, limits the familiarity-associated reductions in heart rate (HR) and breathing frequency (BF) responses during retesting. Methods: Twenty-one cognitively normal older and younger adults (65 ± 2 vs. 26 ± 1 years old) participated in the study. Mini-Mental State Examination (MMSE), Digit-Span-Test (DST), Trail Making Test (TMT-B), and California Verbal Learning Test (CVLT-II) were administered twice at 3-week intervals, while HR and BF were monitored by electrocardiography and plethysmography, respectively. Results: Cognitive performances were not affected by the age factor, and the retest factor only affected CVLT-II. HR and BF increased only in the younger adults (p < .01) during cognitive tests; retesting attenuated these responses (retest factor p < .01). Long-delay free-recall in CVLT-II was unchanged in cognitively normal older versus younger adults. Healthy aging did not diminish short-term memory assessed by DST and CVLT-II short-delay or long-delay free-recalls. Conclusions: Only CVLT-II, but not MMSE, DST or TMT-B, demonstrated cognitive retesting practice effects in the younger and older adults. Cognitive testing at 3-week intervals in cognitively normal older and younger subjects revealed divergent cardiorespiratory responses to MMSE, DST, and TMT-B cognitive testing, particularly HR, which increased only in younger adults and to a lesser extent during retesting despite the absence of practice effects.

Pragmatic approaches to handling practice effects in longitudinal cognitive aging research

INTRODUCTION

The challenge of accounting for practice effects (PEs) when modeling cognitive change was amplified by the COVID-19 pandemic, which introduced period and mode effects that may bias the estimation of cognitive trajectory.

METHODS

In three Kaiser Permanente Northern California prospective cohorts, we compared predicted cognitive trajectories and the association of grip strength with cognitive decline using three approaches: (1) no acknowledgment of PE, (2) inclusion of a wave indicator, and (3) constraining PE based on a preliminary model (APM) fit using a subset of the data.

RESULTS

APM-based correction for PEs based on balanced, pre-pandemic data, and with current age as the timescale produced the smallest discrepancy between within-person and between-person estimated age effects. Estimated associations between grip strength and cognitive decline were not sensitive to the approach used.

DISCUSSION

Constraining PEs based on a preliminary model is a flexible, pragmatic approach allowing for meaningful interpretation of cognitive change.

HIGHLIGHTS

The magnitude of practice effects (PEs) varied widely by study. When PEs were present, the three PE approaches resulted in divergent estimated age-related cognitive trajectories. Estimated age-related cognitive trajectories were sometimes implausible in models that did not account for PEs. The associations between grip strength and cognitive decline did not differ by the PE approach used. Constraining PEs based on estimates from a preliminary model allows for a meaningful interpretation of cognitive change.

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

OBJECTIVE

Practice effects (PE) on cognitive testing have been shown to delay detection of impairment and impede our ability to assess change. When decline over time is expected, as with older adults or progressive diseases, failure to adequately address PEs may lead to inaccurate conclusions because PEs artificially boost scores while pathology- or age-related decline reduces scores. Unlike most methods, a participant-replacement approach can separate pathology- or age-related decline from PEs; however, this approach has only been used across two timepoints. More than two timepoints make it possible to determine if PEs level out after the first follow-up, but it is analytically challenging because individuals may not be assessed at every timepoint.

METHOD

We examined 1,190 older adults who were cognitively unimpaired (n = 809) or had mild cognitive impairment (MCI; n = 381). Participants completed six neuropsychological measures at three timepoints (baseline, 12-month, 24-month). We implemented a participant-replacement method using generalized estimating equations in comparisons of matched returnees and replacements to calculate PEs.

RESULTS

Without accounting for PEs, cognitive function appeared to improve or stay the same. However, with the participant-replacement method, we observed significant PEs within both groups at all timepoints. PEs did not uniformly decrease across time; some-specifically on episodic memory measures-continued to increase beyond the first follow-up.

CONCLUSION

A replacement method of PE adjustment revealed significant PEs across two follow-ups. As expected in these older adults, accounting for PEs revealed cognitive decline. This, in turn, means earlier detection of cognitive deficits, including progression to MCI, and more accurate characterization of longitudinal change. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Resilience resources may buffer some middle-aged and older Black Americans from memory decline despite experiencing discrimination

RATIONALE

Experiences of discrimination have been associated with poorer episodic memory in Black Americans. However, resilience resources at multiple levels (individual, social, and endowed) may act as a buffer to protect future memory decline, especially in the face of discrimination.

OBJECTIVE

Using longitudinal data from the 2006-2016 Health and Retirement Study (N = 1862), we tested whether Black Americans aged 50 and older would show different trajectories of episodic memory depending on their reported experiences of discrimination (everyday and major lifetime) and resilience resources.

METHODS

Analyses were conducted in three steps: (1) joint latent cluster mixed modeling (JLCMM) to estimate the number of classes, (2) barycentric discriminant analyses (BADA) to model the combined influence of discrimination and resilience resources between each memory class, and (3) multinomial regression analyses to explore interactions between discrimination and resilience resources.

RESULTS

JLCMM resulted in three memory classes that differentiated baseline from longitudinal memory performance: "High Decliners," "Low Decliners," and "Low Stable." Two independent patterns described the relationships between the three classes in the context of discrimination and resilience resources. First, compared with High Decliners, the two lower baseline memory classes (Low Decliners and Low Stable) reported more everyday discrimination and lower individual and endowed resilience resources. Second, although the Low Stable class did not report different levels of discrimination, they had more social resilience resources (greater social support and more social contact) than both declining classes.

CONCLUSIONS

Black Americans in later life have heterogeneous patterns of memory trajectories as demonstrated by the three memory classes identified. Those with lower baseline memory experienced more everyday discrimination and had fewer resilience resources compared to those with high baseline performance (High Decliners). Greater social resilience resources were associated with maintained episodic memory over time in Black Americans.

Practice effects in cognitive assessments three years later in non-carriers but not in symptom-free mutation carriers of autosomal-dominant Alzheimer's disease: Exemplifying procedural learning and memory?

Practice effects (PEs) defined as an improvement of performance in cognition due to repeated assessments between sessions are well known in unimpaired individuals, while less is known about impaired cognition and particularly in latent brain disease as autosomal-dominant Alzheimer's disease. The purpose was to evaluate the general (across tests/domains) and domain-specific PE calculated as the annual rate of change (ARC) in relation to years to the estimated disease onset (YECO) and in four groups of AD: asymptomatic mutation carriers (aAD, n = 19), prodromal, i.e., symptomatic mutation carriers, criteria for AD diagnosis not fulfilled (pAD, n = 4) and mutation carriers diagnosed with AD (dAD, n = 6) as well as mutation non-carriers from the AD families serving as a healthy comparison group (HC, n = 35). Cognition was assessed at baseline and follow-up about 3 years later by 12 tests covering six domains. The aAD and HC groups were comparable at baseline in demographic characteristics (age, gender, and education), when they were in their early forties, while the pAD and dAD groups were older and cognitively impaired. The results on mean ARC for the four groups were significantly different, small, positive, and age-insensitive in the HC group, while ARC was negative and declined with time/disease advancement in AD. The differences between HC and aAD groups in mean ARC and domain-specific ARC were not significant, indicating a subtle PE in aAD in the early preclinical stage of AD. In the symptomatic stages of AD, there was no PE probably due to cognitive disease-related progression. PEs were the largest in the verbal domain in both the HC and aAD groups, indicating a relationship with cognitive vulnerability. The group-related difference in mean ARC was predominant in timekeeping tests. To conclude, the practice effect in over 3 years was suggested to be linked to procedural learning and memory.

Practice Effects in Mild Cognitive Impairment Increase Reversion Rates and Delay Detection of New Impairments

Objective

Cognitive practice effects (PEs) can delay detection of progression from cognitively unimpaired to mild cognitive impairment (MCI). They also reduce diagnostic accuracy as suggested by biomarker positivity data. Even among those who decline, PEs can mask steeper declines by inflating cognitive scores. Within MCI samples, PEs may increase reversion rates and thus impede detection of further impairment. Within an MCI sample at baseline, we evaluated how PEs impact prevalence, reversion rates, and dementia progression after 1 year.

Methods

We examined 329 baseline Alzheimer's Disease Neuroimaging Initiative MCI participants (mean age = 73.1; SD = 7.4). We identified test-naïve participants who were demographically matched to returnees at their 1-year follow-up. Since the only major difference between groups was that one completed testing once and the other twice, comparison of scores in each group yielded PEs. PEs were subtracted from each test to yield PE-adjusted scores. Biomarkers included cerebrospinal fluid phosphorylated tau and amyloid beta. Cox proportional models predicted time until first dementia diagnosis using PE-unadjusted and PE-adjusted diagnoses.

Results

Accounting for PEs increased MCI prevalence at follow-up by 9.2% (272 vs. 249 MCI), and reduced reversion to normal by 28.8% (57 vs. 80 reverters). PEs also increased stability of single-domain MCI by 12.0% (164 vs. 147). Compared to PE-unadjusted diagnoses, use of PE-adjusted follow-up diagnoses led to a twofold increase in hazard ratios for incident dementia. We classified individuals as false reverters if they reverted to cognitively unimpaired status based on PE-unadjusted scores, but remained classified as MCI cases after accounting for PEs. When amyloid and tau positivity were examined together, 72.2% of these false reverters were positive for at least one biomarker.

Interpretation

Even when PEs are small, they can meaningfully change whether some individuals with MCI retain the diagnosis at a 1-year follow-up. Accounting for PEs resulted in increased MCI prevalence and altered stability/reversion rates. This improved diagnostic accuracy also increased the dementia-predicting ability of MCI diagnoses.

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

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.

Retest effects in a diverse sample: sociodemographic predictors and possible correction approaches

Repeated cognitive assessment in longitudinal studies favors the occurrence of retest effects, usually increasing the scores obtained at the follow-up assessments when compared to baseline. Therefore, retest effects can compromise the evaluation of cognitive decline in older adults.

Cognitive practice effects delay diagnosis of MCI: Implications for clinical trials

INTRODUCTION

Practice effects (PEs) on cognitive tests obscure decline, thereby delaying detection of mild cognitive impairment (MCI). Importantly, PEs may be present even when there are performance declines, if scores would have been even lower without prior test exposure. We assessed how accounting for PEs using a replacement-participants method impacts incident MCI diagnosis.

METHODS

Of 889 baseline cognitively normal (CN) Alzheimer's Disease Neuroimaging Initiative (ADNI) participants, 722 returned 1 year later (mean age = 74.9 ± 6.8 at baseline). The scores of test-naïve demographically matched "replacement" participants who took tests for the first time were compared to returnee scores at follow-up. PEs-calculated as the difference between returnee follow-up scores and replacement participants scores-were subtracted from follow-up scores of returnees. PE-adjusted cognitive scores were then used to determine if individuals were below the impairment threshold for MCI. Cerebrospinal fluid amyloid beta, phosphorylated tau, and total tau were used for criterion validation. In addition, based on screening and recruitment numbers from a clinical trial of amyloid-positive individuals, we estimated the effect of earlier detection of MCI by accounting for cognitive PEs on a hypothetical clinical trial in which the key outcome was progression to MCI.

RESULTS

In the ADNI sample, PE-adjusted scores increased MCI incidence by 19% (P < .001), increased proportion of amyloid-positive MCI cases (+12%), and reduced proportion of amyloid-positive CNs (-5%; P's < .04). Additional calculations showed that the earlier detection and increased MCI incidence would also substantially reduce necessary sample size and study duration for a clinical trial of progression to MCI. Cost savings were estimated at ≈$5.41 million.

DISCUSSION

Detecting MCI as early as possible is of obvious importance. Accounting for cognitive PEs with the replacement-participants method leads to earlier detection of MCI, improved diagnostic accuracy, and can lead to multi-million-dollar cost reductions for clinical trials.

Short-Term Retest Performance in Young versus Older Adults: Consideration of Integrated Speed-Accuracy Measures

Objectives: The current research addressed gaps in the literature regarding short-term computerized cognitive retest performance in young and older adults using two integrated speed-accuracy metrics. The aims were: (a) to advance the aging literature on short-term retest performance using a computerized cognitive battery and a retest schedule that included both within- and between-day time points, and (b) to assess the test-retest reliability of two integrated speed-accuracy metrics, inverse efficiency scores (IES) and balanced integration scores (BIS).Method: Twenty young (18-23 years) and thirty older (65-71 years) men completed a battery measuring a range of cognitive functions, six times over three testing days, each 1 week apart.Results: Compared to young adults, older adults exhibited steeper within- and between-day performance gains in IES and BIS, which may reflect a combination of lower initial cognitive ability and familiarity, indicating that older adults may require more familiarization on computerized tests. Relative to unadjusted reaction times, IES reliability appeared comparable in older adults, but slightly lower among young adults. The reliability of BIS was lower than unadjusted reaction times and IES in both age groups.Discussion: Our findings provide guidance for researchers wanting to combine speed and accuracy into a single performance metric in repeated testing contexts.

Trends in the Risk of Cognitive Impairment in the United States, 1996-2014

Supplemental Digital Content is available in the text.

Background:

Accumulating evidence suggests risk of cognitive impairment is declining in high-income countries. Much of this research uses longitudinal surveys in which learning over repeated tests may bias results. We analyze trends in cognitive impairment in the United States, accounting for prior test experience and selective mortality.

Methods:

We use the Health and Retirement Study, a population-based, nationally representative panel dataset and include individuals ages 50 years and older in 1996–2014 (n = 32,784). We measure cognitive impairment and dementia using standard cutpoints of the modified Telephone Interview for Cognitive Status. We estimate logistic regression models for any impairment and dementia over time, adjusting for age, sex, and race/ethnicity, comparing models with and without adjustment for practice effects and education. We examine heterogeneity in trends by age, sex, race/ethnicity, and education.

Results:

Models not controlling for test experience suggest that risk of cognitive impairment and dementia decreased over the study period. Controlling for test experience reverses the trend. In our primary models, prevalence of any cognitive impairment increased for women from 18.7% to 21.2% (annual change 0.7%, 95% confidence interval [CI], 0.1%, 1.3%) and for men from 17.6% to 21.0% (annual change 1.0%, CI, 0.5%, 1.4%). For dementia, women’s annual increase was 1.7% (CI, 0.8%, 2.6%) and men’s 2.0% (CI, 1.0%, 2.9%). If not for education, the increase would have been stronger. Increased risk was particularly rapid for Latinas, the least educated, and older ages.

Conclusions:

Risk of cognitive impairment increased from 1996 to 2014. Uncovering determinants of increasing cognitive impairment risk should become a research priority. See video abstract: http://links.lww.com/EDE/B702.

Feasibility and Psychometric Integrity of Mobile Phone-Based Intensive Measurement of Cognition in Older Adults

Background:There is a pressing need for assessment approaches that can be deployed remotely to measure cognitive outcomes in clinical trials and longitudinal aging cohorts. We evaluated the utility of a mobile phone-based intensive measurement study for this purpose. Method:A small cohort of healthy older adults (N = 17, mean age = 73) completed five assessment "bursts" over 12 months, with each measurement burst involving two assessments daily for five consecutive days. Each assessment included brief tests of visual short-term memory and information processing speed, as well as surveys measuring state factors that can affect cognition. Results:At study endpoint we had 94% retention, 97% compliance, and high participant satisfaction. Mobile cognitive test scores demonstrated good reliability, moderate correlations with in-person baseline neuropsychological testing, and significant associations with participant age and education level. Conclusions: Mobile phone-based intensive measurement designs represent a promising assessment approach for measuring cognition longitudinally in older adults.

Live longer, retire later? Developments of healthy life expectancies and working life expectancies between age 50–59 and age 60–69 in Europe

Europe’s population is ageing. Statutory retirement ages are commonly raised to account for continuous increases in life expectancy. In order to estimate the potential to increase statutory and consequently effective retirement ages further, in this study, we investigate the relationship between partial working life expectancy (WLE) and three health expectancies that represent health aspects important for work ability and employability between ages 50 and 59 as well as 60 and 69 for women and men in Europe. We also explore the association between these four indicators and the highest level of educational attainment. We apply Sullivan’s method to estimate WLE and three selected measures that capture general, physical, and cognitive health status of older adults for 26 European countries since 2004. Over time, WLEs increased significantly in the younger age group for women and in the older age group for both sexes. The expected number of years in good physical health have continuously been higher than any of the other three indicators, while the expected number of years in good cognitive health have shown a noticeable increase over time. The investigation of the relationship between education and each life expectancy confirms the well-established positive correlation between education and economic activity as well as good health. Our results indicate potential to extend working lives beyond current levels. However, significant differences in the expected number of years in good health between persons with different levels of education require policies that account for this heterogeneity.

Cognitive Practice Effects Delay Diagnosis; Implications for Clinical Trials

OBJECTIVE

Practice effects on cognitive tests obscure decline, thereby delaying detection of mild cognitive impairment (MCI). This reduces opportunities for slowing Alzheimer's disease progression and can hinder clinical trials. Using a novel method, we assessed the ability of practice-effect-adjusted diagnoses to detect MCI earlier, and tested the validity of these diagnoses based on AD biomarkers.

METHODS

Of 889 Alzheimer's Disease Neuroimaging Initiative participants who were cognitively normal (CN) at baseline, 722 returned at 1-year-follow-up (mean age=74.9±6.8). Practice effects were calculated by comparing returnee scores at follow-up to demographically-matched individuals who had only taken the tests once, with an additional adjustment for attrition effects. Practice effects for each test were subtracted from follow-up scores. The lower scores put additional individuals below the impairment threshold for MCI. CSF amyloid-beta, phosphorylated tau, and total tau were measured at baseline and used for criterion validation.

RESULTS

Practice-effect-adjusted scores increased MCI incidence by 26% (p<.001). Adjustment increased proportions of amyloid-positive MCI cases (+20%) and reduced proportions of amyloid-positive CNs (-6%) (ps<.007). With the increased MCI base rate, adjustment for practice effects would reduce the sample size needed for detecting significant drug treatment effects by an average of 21%, which we demonstrate would result in multi-million-dollar savings in a clinical trial.

INTERPRETATION

Adjusting for practice effects on cognitive testing leads to earlier detection of MCI. When MCI is an outcome, this reduces recruitment needed for clinical trials, study duration, staff and participant burden, and can dramatically lower costs. Importantly, biomarker evidence also indicates improved diagnostic accuracy.

Spousal Education and Cognitive Functioning in Later Life

OBJECTIVES

Numerous studies have documented the relationship between education and cognitive functioning at the individual level. Yet few studies have examined whether a spouse's education spills over to influence the other spouse's cognitive functioning. This study, therefore, investigates the association between spousal education and cognitive functioning, the pathways that may account for this association, and gender differences in this association.

METHOD

Growth curve models were analyzed by using longitudinal couple data from the Health and Retirement Study (N = 5,846 individuals).

RESULTS

More years of spousal education are associated with higher level of cognitive functioning at age 65 (γ000 = 0.0532, 95% confidence interval [CI] = 0.0163-0.0901) and slower decline in cognitive functioning in later adulthood (γ100 = 0.0054, 95% CI = 0.0026-0.0082). The positive association between spousal education and the level of cognitive functioning at age 65 is fully explained by economic resources. The association of spousal education with the rate of change in cognitive functioning decreases but remains significant after controlling for economic resources and health behaviors (γ100 = 0.0043, 95% CI = 0.0014-0.0072). The association between spousal education and cognitive functioning is similar for men and women.

DISCUSSION

Findings suggest that more years of spousal education may slow decline in cognitive functioning for men and women in later life.

Normative Cognitive Decline in Old Age

OBJECTIVE

To characterize trajectories of normative cognitive aging.

METHODS

Older persons without dementia at study enrollment (n = 1,010) had annual cognitive testing for up to 24 years (mean = 9.9 years, standard deviation = 5.0), died, and underwent a neuropathologic examination to quantify 9 postmortem markers of common neurodegenerative and cerebrovascular conditions. To accommodate the heterogeneity in cognitive trajectories, we used functional mixed effects models, which allow individuals to have different patterns of cognitive decline under a unified model structure.

RESULTS

In a functional mixed effects model, postmortem markers (Alzheimer disease pathology, Lewy bodies, transactive response DNA-binding protein 43 pathology, hippocampal sclerosis, atherosclerosis, gross infarcts) were associated with global cognitive decline. Residual global cognitive decline after adjustment for neuropathologic burden was weakly related to age at death; it occurred in only about one-third of participants, mostly proximate to death. Results were comparable after eliminating the initial cognitive assessments to minimize retest learning or controlling for frailty proximate to death. Analyses were also conducted with composite measures of episodic memory and perceptual speed. Residual decline not attributable to neuropathologic burden was confined to a subset for each outcome and was most evident proximate to death. Age at death was unrelated to residual decline in episodic memory but was related to residual decline in perceptual speed.

INTERPRETATION

Late life cognitive loss mainly reflects non-normative pathologic and mortality-related processes rather than normative age-related processes. ANN NEUROL 2020;87:816-829.

Blood Pressure and Cognitive Decline Over 8 Years in Middle-Aged and Older Black and White Americans

Although the association between high blood pressure (BP), particularly in midlife, and late-life dementia is known, less is known about variations by race and sex. In a prospective national study of 22 164 blacks and whites ≥45 years without baseline cognitive impairment or stroke from the REGARDS cohort study (Reasons for Geographic and Racial Differences in Stroke), enrolled 2003 to 2007 and followed through September 2015, we measured changes in cognition associated with baseline systolic and diastolic BP (SBP and DBP), as well as pulse pressure (PP) and mean arterial pressure, and we tested whether age, race, and sex modified the effects. Outcomes were global cognition (Six-Item Screener; primary outcome), new learning (Word List Learning), verbal memory (Word List Delayed Recall), and executive function (Animal Fluency Test). Median follow-up was 8.1 years. Significantly faster declines in global cognition were associated with higher SBP, lower DBP, and higher PP with increasing age ( P<0.001 for age×SBP×follow-up-time, age×DBP×follow-up-time, and age×PP×follow-up-time interaction). Declines in global cognition were not associated with mean arterial pressure after adjusting for PP. Blacks, compared with whites, had faster declines in global cognition associated with SBP ( P=0.02) and mean arterial pressure ( P=0.04). Men, compared with women, had faster declines in new learning associated with SBP ( P=0.04). BP was not associated with decline of verbal memory and executive function, after controlling for the effect of age on cognitive trajectories. Significantly faster declines in global cognition over 8 years were associated with higher SBP, lower DBP, and higher PP with increasing age. SBP-related cognitive declines were greater in blacks and men.

Do people with Alzheimer's disease improve with repeated testing? Unpacking the role of content and context in retest effects

Objective

retest effects may be attributed to 'repeated content' in neuropsychological tests such as words in word list-learning tests, or the 'testing context' which involves procedural memory and reduced test anxiety following repeated administration. Alzheimer's Disease (AD) severely impairs episodic memory, so longitudinal cognitive testing among people with dementia may reveal the relative contributions of content versus context to retest effects in neuropsychological testing.

Method

we used data from the Critical Path Institute's repository of placebo arm data from randomized controlled trials (RCTs) of dementia conducted by participating pharmaceutical companies (N = 990 people, 4,170 study visits, up to 2.4 years of follow-up). To estimate retest effects on the Mini-Mental State Examination (MMSE), we used linear regressions with random effects for people and time, adjusting for age, sex and race, and longitudinal quantile regressions.

Results

average MMSE score (16.6 points, SD = 5.5, range 1, 27) declined by 2.0 points/year (95% confidence interval, CI: -2.3, -1.8). Mean retest effect was 0.6 points (95% CI: 0.4, 0.8) at second assessment (average 4 months after baseline). Retest effects were similar among participants with and without any recall on the short-delay word recall subscale score at baseline, and at the 30th, 50th and 70th percentiles of the MMSE distribution, suggesting similar retest effects across the spectrum from mild to severe cases of dementia.

Conclusions

retest effects are apparent in people with dementia despite reduced episodic memory, suggesting a prominent role of the testing context in RCTs and cohort studies.

Five-year change scores in old age for six neuropsychological tests and normative data for the Useful Field of View (UFOV) test: The influence of physical health

INTRODUCTION

Neuropsychological assessment of cognitive change over time is often conducted in clinical settings, but whether neuropsychological change scores are influenced by physical health has, as far as we know, not been examined previously.

METHOD

In a sample of 153 older Swedish adults (age range, 72-86 years), we evaluated the influence of common age-related diseases, terminal decline pathology, age, education, and gender, to provide (a) preliminary test-specific regression weights and 90% confidence intervals to assess significant change in performance after five years on tests of visual scanning, mental shifting, visual spatial ability, memory, reaction time, and selective attention, and (b) normative data for the Useful Field of View test (UFOV) from a single testing occasion.

RESULTS

Multiple regression analyses showed that test-retest changes were affected by physical health for mental shifting, visual spatial ability, memory, and reaction time, by age for mental shifting and visual reaction time, by education for visual spatial ability, and by Age × Education for auditory reaction time. Gender did not affect any of the change scores. The overall average of variance explained was 2.5%: up to 8.1% for physical health, 4.4% for age, and 3.6% for education. The UFOV scores were mostly influenced by age, but also by physical health and education.

CONCLUSIONS

The findings indicate that considering the influence of health on normative change scores in old age in addition to demographic factors leads to more accurate predictions of whether true change has occurred.

Change in Cognitive Performance From Midlife Into Old Age: Findings from the Midlife in the United States (MIDUS) Study

OBJECTIVES

A substantial body of research has documented age-related declines in cognitive abilities among adults over 60, yet there is much less known about changes in cognitive abilities during midlife. The goal was to examine longitudinal changes in multiple cognitive domains from early midlife through old age in a large national sample, the Midlife in the United States (MIDUS) study.

METHODS

The Brief Test of Adult Cognition by Telephone (BTACT) was administered on two occasions (MIDUS 2, MIDUS 3), an average of 9 years apart. At MIDUS 3, those with the cognitive assessment (N=2518) ranged in age from 42 to 92 years (M=64.30; SD=11.20) and had a mean education of 14.68 years (SD=2.63). The BTACT includes assessment of key aging-sensitive cognitive domains: immediate and delayed free recall, number series, category fluency, backward digit span, processing speed, and reaction time for attention switching and inhibitory control, which comprise two factors: episodic memory and executive functioning.

RESULTS

As predicted, all cognitive subtests and factors showed very small but significant declines over 9 years, with differences in the timing and extent of change. Processing speed showed the earliest and steepest decrements. Those with higher educational attainment scored better on all tests except reaction time. Men had better executive functioning and women performed better on episodic memory.

CONCLUSIONS

Examining cognitive changes in midlife provides opportunities for early detection of cognitive impairments and possibilities for preventative interventions. (JINS, 2018, 24, 805-820).

Correction for retest effects across repeated measures of cognitive functioning: a longitudinal cohort study of postoperative delirium

BACKGROUND

Few studies have compared methods to correct for retest effects or practice effects in settings where an acute event could influence test performance, such as major surgery. Our goal in this study was to evaluate the use of different methods to correct for the effects of practice or retest on repeated test administration in the context of an observational study of older adults undergoing elective surgery.

METHODS

In a cohort of older surgical patients (N = 560) and a non-surgical comparison group (N = 118), we compared changes on repeated cognitive testing using a summary measure of general cognitive performance (GCP) between patients who developed post-operative delirium and those who did not. Surgical patients were evaluated pre-operatively and at 1, 2, 6, 12, and 18 months following surgery. Inferences from linear mixed effects models using four approaches were compared: 1) no retest correction, 2) mean-difference correction, 3) predicted-difference correction, and 4) model-based correction.

RESULTS

Using Approaches 1 or 4, which use uncorrected data, both surgical groups appeared to improve or remain stable after surgery. In contrast, Approaches 2 and 3, which dissociate retest and surgery effects by using retest-adjusted GCP scores, revealed an acute decline in performance in both surgical groups followed by a recovery to baseline. Relative differences between delirium groups were generally consistent across all approaches: the delirium group showed greater short- and longer-term decline compared to the group without delirium, although differences were attenuated after 2 months. Standard errors and model fit were also highly consistent across approaches.

CONCLUSION

All four approaches would lead to nearly identical inferences regarding relative mean differences between groups experiencing a key post-operative outcome (delirium) but produced qualitatively different impressions of absolute performance differences following surgery. Each of the four retest correction approaches analyzed in this study has strengths and weakness that should be evaluated in the context of future studies. Retest correction is critical for interpretation of absolute cognitive performance measured over time and, consequently, for advancing our understanding of the effects of exposures such as surgery, hospitalization, acute illness, and delirium.

Neurodegenerative disease and cognitive retest learning

Retest learning impacts estimates of cognitive aging, but its bases are uncertain. Here, we test the hypothesis that dementia-related neurodegeneration impairs retest learning. Older persons without cognitive impairment at enrollment (n = 567) had annual cognitive testing for a mean of 11 years, died, and had a neuropathologic examination to quantify 5 neurodegenerative pathologies. Change point models were used to divide cognitive trajectories into an early retest sensitive component and a later component less sensitive to retest. Performance on a global cognitive measure (baseline mean = 0.227, standard deviation = 0.382) increased an estimated mean of 0.142-unit per year for a mean of 1.5 years and declined an estimated mean of 0.123-unit per year thereafter. No pathologic marker was related to cognitive change before the change point; each was related to cognitive decline after the change point. Results were comparable in analyses that used specific cognitive outcomes, included 220 individuals with mild cognitive impairment at enrollment, or allowed a longer retest learning period. The findings suggest that neurodegeneration does not impact cognitive retest learning.

Cohort effects in verbal memory function and practice effects: a population-based study

BACKGROUND

In many developed countries, cognitive functioning (as measured by neuropsychological tests) appears to be improving over time in the population at large, in parallel with the declining age-specific incidence of dementia. Here, we investigated cohort effects in the age-associated trajectories of verbal memory function in older adults. We sought to determine whether they varied by decade of birth and, if so, whether the change would be explained by increasing educational attainment.

METHODS

Pooling data from two prospective US population-based studies between 1987 and 2015, we identified four birth cohorts born 1902-1911, 1912-1921, 1922-1931, and 1932-1943. Among these cohorts, we compared age-associated trajectories both of performance and of practice effects on immediate and delayed recall of a 10-item Word List. We used mixed effects models, first including birth cohorts and cohort X age interaction terms, and then controlling for education and education X age interaction.

RESULTS

We observed significant cohort effects in performance (baseline and age-associated trajectories) in both immediate recall and delayed recall, with function improving between the earliest- and latest-born cohorts. For both tests, we also observed cohort effects on practice effects with the highest levels in the latest-born cohorts. Including education in the models did not attenuate these effects.

CONCLUSIONS

In this longitudinal population study, across four decade-long birth cohorts, there were significant improvements in test performance and practice effects in verbal memory tests, not explained by education. Whether this reflects declining disease incidence or other secular trends awaits further investigation.

Modeling practice effects in healthy middle-aged participants of the Alzheimer and Families parent cohort

Introduction

Repetitive administration of neuropsychological tests can lead to performance improvement merely due to previous exposure. The magnitude of such practice effects (PEs) may be used as a marker of subtle cognitive impairment because they are diminished in healthy individuals subsequently developing Alzheimer's disease (AD).

Methods

To explore the relationship between sociodemographic factors, AD family history (FH), and APOE ε4 status, and the magnitude of PE, four subtests of the Wechsler Adult Intelligence Scale-IV were administered twice to 400 middle-aged healthy individuals, most of them first-degree descendants of AD patients.

Results

PEs were observed in all measures. Sociodemographic variables did not show a uniform effect on PE. Baseline score was the strongest predictor of change, being inversely related to PE magnitude. Significant effects of the interaction term APOE ε4^∗Age in processing speed and working memory were observed.

Discussion

PEs exert a relevant effect in cognitive outcomes at retest and, accordingly, they must be taken into consideration in clinical trials. The magnitude of PE in processing speed and working memory could be of special interest for the development of cognitive markers of preclinical AD.

The role of early-life educational quality and literacy in explaining racial disparities in cognition in late life

OBJECTIVES

Racial disparities in late-life cognition persist even after accounting for educational attainment. We examined whether early-life educational quality and literacy in later life help explain these disparities.

METHOD

We used longitudinal data from the Washington Heights-Inwood Columbia Aging Project (WHICAP). Educational quality (percent white students; urban/rural school; combined grades in classroom) was operationalized using canonical correlation analysis. Late-life literacy (reading comprehension and ability, writing) was operationalized using confirmatory factor analysis. We examined whether these factors attenuated race-related differences in late-life cognition.

RESULTS

The sample consisted of 1,679 U.S.-born, non-Hispanic, community-living adults aged 65-102 (71% black, 29% white; 70% women). Accounting for educational quality and literacy reduced disparities by 29% for general cognitive functioning, 26% for memory, and 32% for executive functioning but did not predict differences in rate of cognitive change.

DISCUSSION

Early-life educational quality and literacy in late life explain a substantial portion of race-related disparities in late-life cognitive function.

Relationship Between Type 2 Diabetes Mellitus and Cognitive Change in a Multiethnic Elderly Cohort

OBJECTIVES

To examine the association between diabetes mellitus and cognitive functioning at baseline and cognitive change over time in a large, ethnically diverse sample of older adults.

DESIGN

Prospective cohort study.

SETTING

Washington Heights-Inwood Columbia Aging Project, a community-based, prospective study of risk factors for dementia in northern Manhattan, New York City.

PARTICIPANTS

Hispanic, non-Hispanic black, and non-Hispanic white men and women aged 65 and older without dementia at baseline (N = 1,493).

MEASUREMENTS

Participants underwent baseline and follow-up cognitive and health assessments approximately every 18 months. Generalized estimating equations were used to examine the longitudinal association between diabetes mellitus and cognition.

RESULTS

Diabetes mellitus was associated with poorer baseline cognitive performance in memory, language, processing speed and executive functioning, and visuospatial abilities. After adjusting for age, education, sex, race and ethnicity, and apolipoprotein-ε4, participants with diabetes mellitus performed significantly worse at baseline than those without in language and visuospatial abilities. There were no differences between those with and without diabetes mellitus in terms of rate of cognitive change over a mean follow-up time of 6 years.

CONCLUSION

The rate of cognitive change in elderly persons with and without diabetes mellitus is similar, although cognitive performance is poorer in persons with diabetes mellitus. These findings suggest that cognitive changes may occur early during the diabetes mellitus process and highlight the need for studies to follow participants beginning at least in midlife, before the typical later-life onset of dementia.