Application and validation of an algorithmic classification of early impairment in cognitive performance

OBJECTIVE

Due to the long prodromal period for dementia pathology, approaches are needed to detect cases before clinically recognizable symptoms are apparent, by which time it is likely too late to intervene. This study contrasted two theoretically-based algorithms for classifying early cognitive impairment (ECI) in adults aged ≥50 enrolled in the Baltimore Longitudinal Study of Aging.

METHOD

Two ECI algorithms were defined as poor performance (1 standard deviation [SD] below age-, sex-, race-, and education-specific means) in: (1) Card Rotations or California Verbal Learning Test (CVLT) immediate recall and (2) ≥1 (out of 2) memory or ≥3 (out of 6) non-memory tests. We evaluated concurrent criterion validity against consensus diagnoses of mild cognitive impairment (MCI) or dementia and global cognitive scores using receiver operating characteristic (ROC) curve analysis. Predictive criterion validity was evaluated using Cox proportional hazards models to examine the associations between algorithmic status and future adjudicated MCI/dementia.

RESULTS

Among 1,851 participants (mean age = 65.2 ± 11.8 years, 50% women, 74% white), the two ECI algorithms yielded comparably moderate concurrent criterion validity with adjudicated MCI/dementia. For predictive criterion validity, the algorithm based on impairment in Card Rotations or CVLT immediate recall was the better predictor of MCI/dementia (HR = 3.53, 95%CI: 1.59-7.84) over 12.3 follow-up years.

CONCLUSIONS

Impairment in visuospatial ability or memory may be capable of detecting early cognitive changes in the preclinical phase among cognitively normal individuals.

Associations Between Objectively Measured Sleep and Cognition: Main Effects and Interactions With Race in Adults Aged ≥50 Years

BACKGROUND

This study examined associations of actigraphy-estimated sleep parameters with concurrent and future cognitive performance in adults aged ≥ 50 years and explored interactions with race.

METHODS

Participants were 435 cognitively normal adults in the Baltimore Longitudinal Study of Aging who completed wrist actigraphy at baseline (mean = 6.6 nights) and underwent longitudinal testing of memory, attention, executive function, language, and visuospatial ability. On average, participants with follow-up data were followed for 3.1 years. Primary predictors were baseline mean total sleep time, sleep onset latency, sleep efficiency (SE), and wake after sleep onset (WASO). Fully adjusted linear mixed-effects models included demographics, baseline health-related characteristics, smoking status, sleep medication use, APOE e4 carrier status, and interactions of each covariate with time.

RESULTS

In adjusted models, higher SE (per 10%; B = 0.11, p = .012) and lower WASO (per 30 minutes; B = -0.12, p = .007) were associated with better memory cross-sectionally. In contrast, higher SE was associated with greater visuospatial ability decline longitudinally (B = -0.02, p = .004). Greater WASO was associated with poorer visuospatial ability cross-sectionally (B = -0.09, p = .019) but slower declines in visuospatial abilities longitudinally (B = 0.02, p = .002). Several sleep-cognition cross-sectional and longitudinal associations were stronger in, or limited to, Black participants (compared to White participants).

CONCLUSIONS

This study suggests cross-sectional sleep-cognition associations differ across distinct objective sleep parameters and cognitive domains. This study also provides preliminary evidence for racial differences across some sleep-cognition relationships. Unexpected directions of associations between baseline sleep and cognitive performance over time may be attributable to the significant proportion of participants without follow-up data and require further investigation.

Application and validation of an algorithmic classification of early impairment in cognitive performance

Objective

Due to the long prodromal period for dementia pathology, approaches are needed to detect cases before clinically recognizable symptoms are apparent, by which time it is likely too late to intervene. This study contrasted two theoretically-based algorithms for classifying early cognitive impairment (ECI) in adults aged ≥50 enrolled in the Baltimore Longitudinal Study of Aging.

Method

Two ECI algorithms were defined as poor performance (1 standard deviation [SD] below age-, sex-, race-, and education-specific means) in: (1) Card Rotations or California Verbal Learning Test (CVLT) immediate recall and (2) ≥1 (out of 2) memory or ≥3 (out of 6) non- memory tests. We evaluated concurrent criterion validity against consensus diagnoses of mild cognitive impairment (MCI) or dementia and global cognitive scores using receiver operating characteristic (ROC) curve analysis. Predictive criterion validity was evaluated using Cox proportional hazards models to examine the associations between algorithmic status and future adjudicated MCI/dementia.

Results

Among 1,851 participants (mean age=65.2±11.8 years, 50% women, 74% white), the two ECI algorithms yielded comparably moderate concurrent criterion validity with adjudicated MCI/dementia. For predictive criterion validity, the algorithm based on impairment in Card Rotations or CVLT immediate recall was the better predictor of MCI/dementia (HR=3.53, 95%CI: 1.59-7.84) over 12.3 follow-up years.

Conclusions

Impairment in visuospatial ability or memory may be capable of detecting early cognitive changes in the preclinical phase among cognitively normal individuals.

PET OWNERSHIP AND MAINTENANCE OF EXECUTIVE FUNCTION IN OLDER ADULTS– EVIDENCE FROM THE BLSA

Pet ownership (PO) or human-animal interaction (HAI) has been associated with better physical and mental health in individuals with existing disease or disability. In experimental studies, HAI improves some aspects of cognitive function. No research addresses HAI and longitudinal changes in cognitive function in older adults. We examined the relationship of PO to maintaining executive function (EF) within generally healthy community-dwelling older adults in the Baltimore Longitudinal Study of Aging (BLSA). We hypothesized less EF deterioration among pet owners than non-owners; and less deterioration among dog-walkers than owners who don’t walk their dogs. 637 women (55.9%) and men aged 50–100 years (M=68.3, SD=9.6) completed a PO questionnaire which ascertained ownership history and comprehensive examination every 1–4 years over 1–13 years (M=7.5, SD=3.6). Linear mixed models with time varying PO examined changes in EF according to PO. Pet owners (n=185) were younger (p < 0.001) and healthier (p=0.030) than non-owners; thus, age and comorbidities were included as covariates in the longitudinal analyses. EF, assessed using the Trail-Making Test (TMT), deteriorated with age (p’s < 0.001). Deterioration was less severe among pet owners than non-owners (TMT A: p < 0.001; B: p < 0.001; difference: p=0.042) and dog owners than non-owners (TMT A: p=0.025; B: p=0.009; difference: p=0.076), but not among cat owners than non-owners. Among dog owners (n=73), dog walkers experienced less deterioration than non-walkers (TMT A: p=0.156; B: p=0.001; difference: p < 0.001). This study provides the first longitudinal evidence that PO may contribute to maintaining EF among community-dwelling generally healthy older adults as they age.

Prognostic Value of Learning and Retention Measures from the Free and Cued Selective Reminding Test to Identify Incident Mild Cognitive Impairment

OBJECTIVE

To compare the predictive validity of learning and retention measures from the picture version of the Free and Cued Selective Reminding Test with Immediate Recall (pFCSRT + IR) for identifying incident mild cognitive impairment (MCI).

METHODS

Learning was defined by the sum of free recall (FR) and retention by delayed free recall (DFR) tested 15-20 min later. Totally, 1422 Baltimore Longitudinal Study of Aging (BLSA) participants (mean age 69.6 years, 54% male, mean 16.7 years of education) without dementia or MCI received the pFCSRT + IR at baseline and were followed longitudinally. Cox proportional hazards models were used to evaluate the effect of baseline learning and retention on risk of MCI.

RESULTS

In total, 187 participants developed MCI over a median of 8.1 years of follow-up. FR and DFR each predicted incident MCI adjusting for age, sex, and education. Also, each independently predicted incident MCI in the presence of the other with similar effect sizes: around 20% decrease in the hazard of MCI corresponding to one standard deviation increase in FR or DFR.

CONCLUSION

The practice of preferring retention over learning to predict incident MCI should be reconsidered. The decision to include retention should be guided by time constraints and patient burden.

Profiles of Cognitive Change in Preclinical and Prodromal Alzheimer's Disease Using Change-Point Analysis

BACKGROUND

Alzheimer's disease (AD) is now understood to have a long preclinical phase in which pathology starts to accumulate in the absence of clinical symptoms. Identifying the temporal stages of accelerated cognitive decline in this phase may help in developing more sensitive neuropsychological tools for early screening of preclinical cognitive decline. Change-point analyses are increasingly used to characterize the temporal stages of accelerated cognitive decline in the preclinical stages of AD. However, statistical comparisons of change-points between specific cognitive measures have not been reported.

OBJECTIVE

To characterize and compare the temporal stages of accelerated decline in performance on multiple cognitive tests in a sample of participants from the Baltimore Longitudinal Study on Aging (BLSA) who later developed AD.

METHODS

165 older adults (baseline age range: 61.1-91.2) from the BLSA developed AD during follow-up. Linear and non-linear mixed models were fit for 11 cognitive measures to determine change-points in rates of decline before AD diagnosis. Bootstrapping was used to compare the timing of change-points across cognitive measures.

RESULTS

Change-points followed by accelerated decline ranged from 15.5 years (Standard Error (S.E.) = 1.72) for Card Rotations to 1.9 years (S.E. = 0.68) for the Trail-Making Test Part A before AD diagnosis. Accelerated decline in Card Rotations occurred significantly earlier than all other measures, including learning and memory measures.

CONCLUSION

Results suggest that visuospatial ability, as assessed by Card Rotations, may have the greatest utility as an early predictive tool in identifying preclinical AD.

Pet Ownership Patterns and Successful Aging Outcomes in Community Dwelling Older Adults

Introduction: Diminishing cognitive and physical functions, worsening psychological symptoms, and increased mortality risk and morbidity typically accompany aging. The aging population's health needs will continue to increase as the proportion of the population aged > 50 years increases. Pet ownership (PO) has been linked to better health outcomes in older adults, particularly those with chronic conditions. Much of the evidence is weak. Little is known about PO patterns as people age or the contribution of PO to successful aging in community-dwelling older adults. This study examines PO patterns among healthy community-dwelling older adults and the relationship of PO to cognitive and physical functions and psychological status. Methods: Participants in the Baltimore Longitudinal Study of Aging (> 50 years old, N = 378) completed a battery of cognitive, physical function, and psychological tests, as well as a PO questionnaire. Descriptive and non-parametric or general/generalized linear model analyses were conducted for separate outcomes. Results: Most participants (82%) had kept pets and 24% have pets: 14% dogs, 12% cats, 3% other pets. The most frequent reasons for having pets included enjoyment (80%) and companionship (66%). Most owners had kept the pet they had the longest for over 10 years (70%). PO was lower in older decades (p < 0.001). Pet owners were more likely to live in single-family homes and reside with others (p = 0.001) than non-owners. Controlling for age, PO was associated independently with better cognitive function (verbal leaning/memory p = 0.041), dog ownership predicted better physical function (daily energy expenditure, p = 0.018), and cat ownership predicted better cognitive functioning (verbal learning/memory, p = 0.035). Many older adults who did not own pets (37%) had regular contact with pets, which was also related to health outcomes. Conclusion: PO is lower at older ages, which mirrors the general pattern of poorer cognitive and physical function, and psychological status at older ages. PO and regular contact with pets (including PO) are associated with better cognitive status compared with those who did not own pets or had no regular contact with pets independent of age. Dog ownership was related to better physical function. Longitudinal analysis is required to evaluate the association of PO and/or regular contact with maintenance of health status over time.

Apolipoprotein E ε4 allele effects on longitudinal cognitive trajectories are sex and age dependent

INTRODUCTION

Questions remain about whether apolipoprotein E (APOE)-ε4 effects on cognitive decline are similar in men and women and how APOE-ε4 and age interact to influence decline in different cognitive domains.

METHODS

In sex-stratified analyses, baseline age-dependent associations between APOE-ε4 status and longitudinal cognitive trajectories were examined in cognitively normal Caucasian older adults (631 men, 561 women, baseline age range: 50-93, 6733 assessments).

RESULTS

In men, older baseline age was associated with greater effects of APOE-ε4 on longitudinal decline in memory and executive function, detectible from baseline age of 64 and 68, respectively. In women, older baseline age was associated with greater APOE-ε4 effects on longitudinal decline in attention, detectible at baseline age of 66. No significant APOE-ε4 effects were found for language, visual-spatial ability, or processing speed.

DISCUSSION

Results highlight the importance of considering sex and age when assessing APOE-ε4-associated vulnerability to cognitive decline.

A classification algorithm for predicting progression from normal cognition to mild cognitive impairment across five cohorts: The preclinical AD consortium

INTRODUCTION

We established a method for diagnostic harmonization across multiple studies of preclinical Alzheimer's disease and validated the method by examining its relationship with clinical status and cognition.

METHODS

Cognitive and clinical data were used from five studies (N = 1746). Consensus diagnoses established in each study used criteria to identify progressors from normal cognition to mild cognitive impairment. Correspondence was evaluated between these consensus diagnoses and three algorithmic classifications based on (1) objective cognitive impairment in 2+ tests only; (2) a Clinical Dementia Rating (CDR) of ≥0.5 only; and (3) both. Associations between baseline cognitive performance and cognitive change were each tested in relation to progression to algorithm-based classifications.

RESULTS

In each study, an algorithmic classification based on both cognitive testing cutoff scores and a CDR ≥0.5 provided optimal balance of sensitivity and specificity (areas under the curve: 0.85-0.95). Over an average 6.6 years of follow-up (up to 28 years), N = 186 initially cognitively normal participants aged on average 64 years at baseline progressed (incidence rate: 15.3 people/1000 person-years). Baseline cognitive scores and cognitive change were associated with future diagnostic status using this algorithmic classification.

DISCUSSION

Both cognitive tests and CDR ratings can be combined across multiple studies to obtain a reliable algorithmic classification with high specificity and sensitivity. This approach may be applicable to large cohort studies and to clinical trials focused on preclinical Alzheimer's disease because it provides an alternative to implementation of a time-consuming adjudication panel.

Blood metabolite markers of cognitive performance and brain function in aging

We recently showed that Alzheimer's disease patients have lower plasma concentrations of the phosphatidylcholines (PC16:0/20:5; PC16:0/22:6; and PC18:0/22:6) relative to healthy controls. We now extend these findings by examining associations between plasma concentrations of these PCs with cognition and brain function (measured by regional resting state cerebral blood flow; rCBF) in non-demented older individuals. Within the Baltimore Longitudinal Study of Aging neuroimaging substudy, participants underwent cognitive assessments and brain (15)O-water positron emission tomography. Plasma phosphatidylcholines concentrations (PC16:0/20:5, PC16:0/22:6, and PC18:0/22:6), cognition (California Verbal Learning Test (CVLT), Trail Making Test A&B, the Mini-Mental State Examination, Benton Visual Retention, Card Rotation, and Fluencies-Category and Letter), and rCBF were assessed. Lower plasma phosphatidylcholine concentrations were associated with lower baseline memory performance (CVLT long delay recall task-PC16:0/20:5: -2.17-1.39-0.60 p = 0.001 (β with 95% confidence interval subscripts)) and lower rCBF in several brain regions including those associated with memory performance and higher order cognitive processes. Our findings suggest that lower plasma concentrations of PC16:0/20:5, PC16:0/22:6, and PC18:0/22:6 are associated with poorer memory performance as well as widespread decreases in brain function during aging. Dysregulation of peripheral phosphatidylcholine metabolism may therefore be a common feature of both Alzheimer's disease and age-associated differences in cognition.

Literacy-based normative data for low socioeconomic status African Americans

Clinical neuropsychology relies on the use of appropriate test norms. Normative studies frequently stratify based on age, education, sex, and race. None to date has reported norms based on literacy, despite the substantial evidence that literacy impacts cognitive functioning. Some researchers have suggested that literacy is a more accurate reflection of academic achievement and quality of education than years of education, particularly for African Americans. The current study provides literacy-based normative data for multiple neuropsychological measures based on a sample of predominantly low socioeconomic status African Americans. These normative data should improve the diagnostic accuracy of performances by African-American clients with similar demographic backgrounds.

Factorial invariance of the CES-D in low socioeconomic status African Americans compared with a nationally representative sample

This study examined the factor structure of the Center for Epidemiologic Studies Depression Scale (CES-D) in low socioeconomic status African Americans (n=426). Confirmatory factor analysis indicated that the four factors-(1) depressed affect, (2) positive affect, (3) somatic complaints, and (4) interpersonal problems-of the CES-D scale previously found in the general population were supported in this sample. These results were cross-validated in other nationally representative samples of African-American participants (n=988) and Caucasians (n=666), and the four-factor structure of the CES-D scale replicated in all three groups in this study. An alternative model was also tested with the factors depressed affect and somatic complaints combined as a single factor, a finding often reported in minority groups. Results indicated a significantly poorer fit for the three-factor model compared with the four-factor model for all three groups. In addition, higher loading differences were significantly evident between African-American and Caucasian groups, while higher loading similarities were found between the two African-American groups. These findings provide further evidence of measurement equivalency of the CES-D scale in samples with differential characteristics including race and socioeconomic status.

Self-generated happy and sad emotions in low and highly hypnotizable persons during waking and hypnosis: laterality and regional EEG activity differences

EEG correlates of self-generated happy and sad emotions during counterbalanced conditions of waking and hypnosis were investigated in 16 low ("lows') and 15 highly ("highs') hypnotizable men, as assessed by the Harvard Group Scale of Hypnotic Susceptibility and the Stanford Hypnotic Susceptibility Scale, Form C. Using log mean spectral magnitude, 11 frequency bands (3.5-42 Hz) were evaluated at frontal (F3, F4), central (C3, C4), and parietal (P3, P4) regions. As anticipated, only parietal hemispheric differences in low alpha activity (7.5-9.45 Hz) differentiated between emotions, whereas mid and high alpha activity (9.5-13.45 Hz) did not. There was significantly less low alpha activity in right parietal (P4) in sad than happy emotions, supportive of prior research showing relatively greater right hemispheric involvement in negative than positive emotions. Yet, overall there was more low alpha activity in the left parietal (P3) region. During sadness only in waking, low beta (13.5-15.45 Hz) activity was greater in the right than left frontal region, greater in the left than right central region, and similar in both hemispheres in the parietal region. As anticipated, in comparison to lows, highs showed significantly greater hemispheric asymmetries (right greater than left) in the parietal region in high theta (5.5-7.45 Hz), high alpha (11.5-13.45 Hz), and beta activity between 16.5 and 25 Hz-all frequency bands that are associated with sustained attentional processing. Results support prior research (for reviews, see Crawford, 1994a; Crawford and Gruzelier, 1992) that highs have greater sustained attentional abilities than do lows, which is reflected in different regional brain dynamics. Future EEG research needs to address narrower EEG frequency bands, as well as consider the moderating effects of hypnotic susceptibility level in observed hemispheric asymmetries.

Transient positive and negative experiences accompanying stage hypnosis

Frequency of positive and negative experiences accompanying stage hypnosis was assessed in follow-up interviews with 22 participants of university-sponsored performances. Most subjects described their experience positively (relaxing, interesting, exciting, satisfying, illuminating, and pleasurable), but some described it negatively (confusing, silly, annoying, and frightening). Five subjects (22.7%) reported partial or complete amnesia; all were highly responsive to the stage hypnosis suggestions. One subject was completely unable to breach amnesia and felt annoyed and frightened. Five subjects (22.7%) believed the hypnotist had control over their behavior. Participants (n = 15) tested subsequently on the Stanford Hypnotic Susceptibility Scale, Form C (Weitzenhoffer & Hilgard, 1962) were mostly moderately to highly hypnotizable (M = 7.07), and the scores correlated significantly (r = .68) with the percentage of passed stage hypnosis suggestions.

Transient positive and negative experiences accompanying stage hypnosis

Frequency of positive and negative experiences accompanying stage hypnosis was assessed in follow-up interviews with 22 participants of university-sponsored performances. Most subjects described their experience positively (relaxing, interesting, exciting, satisfying, illuminating, and pleasurable), but some described it negatively (confusing, silly, annoying, and frightening). Five subjects (22.7%) reported partial or complete amnesia; all were highly responsive to the stage hypnosis suggestions. One subject was completely unable to breach amnesia and felt annoyed and frightened. Five subjects (22.7%) believed the hypnotist had control over their behavior. Participants (n = 15) tested subsequently on the Stanford Hypnotic Susceptibility Scale, Form C (Weitzenhoffer & Hilgard, 1962) were mostly moderately to highly hypnotizable (M = 7.07), and the scores correlated significantly (r = .68) with the percentage of passed stage hypnosis suggestions.