Two of the most commonly used methods to assess memory functioning in studies of cognitive aging and dementia are story memory and list learning tests. We hypothesized that the most commonly used story memory test, Wechsler's Logical Memory, would generate more pronounced practice effects than a well validated but less common list learning test, the Neuropsychological Assessment Battery (NAB) List Learning test. Two hundred eighty-seven older adults, ages 51 to 100 at baseline, completed both tests as part of a larger neuropsychological test battery on an annual basis. Up to five years of recall scores from participants who were diagnosed as cognitively normal (n = 96) or with mild cognitive impairment (MCI; n = 72) or Alzheimer's disease (AD; n = 121) at their most recent visit were analyzed with linear mixed effects regression to examine the interaction between the type of test and the number of times exposed to the test. Other variables, including age at baseline, sex, education, race, time (years) since baseline, and clinical diagnosis were also entered as fixed effects predictor variables. The results indicated that both tests produced significant practice effects in controls and MCI participants; in contrast, participants with AD declined or remained stable. However, for the delayed—but not the immediate—recall condition, Logical Memory generated more pronounced practice effects than NAB List Learning (b = 0.16, p < .01 for controls). These differential practice effects were moderated by clinical diagnosis, such that controls and MCI participants—but not participants with AD—improved more on Logical Memory delayed recall than on delayed NAB List Learning delayed recall over five annual assessments. Because the Logical Memory test is ubiquitous in cognitive aging and neurodegenerative disease research, its tendency to produce marked practice effects—especially on the delayed recall condition—suggests a threat to its validity as a measure of new learning, an essential construct for dementia diagnosis.
Sleep disturbances are common in Parkinson's disease (PD). Actigraphy has emerged as an alternative to polysomnography to measure sleep, raising the question of its ability to capture sleep quality in PD patients. Our aim was to compare self-report data with actigraphic data and to examine associations with clinical variables. Thirty non-demented individuals with PD and 14 normal control participants (NC) were included. Sleep was measured using 24-hour wrist actigraphy over a seven-day period, during which time participants kept a sleep diary. Subjective sleep and arousal questionnaires included the Parkinson's Disease Sleep Scale, and Epworth Sleepiness Scale. Patients with PD presented with more sleep problems than NC. In NC, none of the actigraphic sleep variables were related to any of the self-report measures of sleep. In PD, scores on subjective sleep measures correlated with actigraphy-derived estimates of sleep quality. Our results suggest that actigraphy is an appropriate method of measuring sleep quality in PD.
Background Dementia severity can be modeled as the construct δ, representing the “cognitive correlates of functional status.” Objective We recently validated a model for estimating δ in the National Alzheimer’s Coordinating Center’s Uniform Data Set; however, δ’s association with neuropathology remains untested. Methods We used data from 727 decedents evaluated at Alzheimer’s Disease (AD) Centers nationwide. Participants spoke English, had no genetic abnormalities, and were pathologically diagnosed with AD as a primary or contributing etiology. Clinical data from participants’ last visit prior to death were used to estimate dementia severity (δ). Results A structural equation model using age, education, race, and apolipoprotein E (APOE) genotype (number of ε2 and ε4 alleles) as predictors and latent AD pathology and cerebrovascular disease (CVD) pathology as mediators fit the data well (RMSEA = 0.031; CFI = .957). AD pathology mediated the effects of age and APOE genotype on dementia severity. An older age at death and more ε2 alleles were associated with less AD pathology and, in turn, with less severe dementia. In contrast, more ε4 alleles were associated with more pathology and more severe dementia. Although age and race contributed to differences in CVD pathology, CVD pathology was not related to dementia severity in this sample of decedents with pathologically confirmed AD. Conclusions Using δ as an estimate of dementia severity fits well within a structural model in which AD pathology directly affects dementia severity and mediates the relationship between age and APOE genotype on dementia severity.
Objective Two main approaches to the interpretation of cognitive test performance have been utilized for the characterization of disease: evaluating shared variance across tests, as with measures of severity, and evaluating the unique variance across tests, as with pattern and error analysis. Both methods provide necessary information, but the unique contributions of each are rarely considered. This study compares the two approaches on their ability to differentially diagnose with accuracy, while controlling for the influence of other relevant demographic and risk variables. Method Archival data requested from the NACC provided clinical diagnostic groups that were paired to one another through a genetic matching procedure. For each diagnostic pairing, two separate logistic regression models predicting clinical diagnosis were performed and compared on their predictive ability. The shared variance approach was represented through the latent phenotype δ, which served as the lone predictor in one set of models. The unique variance approach was represented through raw score values for the 12 neuropsychological test variables comprising δ, which served as the set of predictors in the second group of models. Results Examining the unique patterns of neuropsychological test performance across a battery of tests was the superior method of differentiating between competing diagnoses, and it accounted for 16-30% of the variance in diagnostic decision making. Conclusion Implications for clinical practice are discussed, including test selection and interpretation.
The serial position effect reveals that recall of a supraspan list of words follows a predictable pattern, whereby words at the beginning (primacy) and end (recency) of a list are recalled more easily than words in the middle. This effect has typically been studied using single list-learning trials, but in neuropsychology, multi-trial list-learning tests are more commonly used. The current study examined trends in learning for primacy, middle, and recency effects across multiple trials in younger and older age cohorts. Participants were 158 volunteers, including 79 adults aged 17-36 ("younger" group) and 79 adults aged 54-89 years ("older" group). Each participant completed four learning trials and one delayed (5-10 min) recall trial from the Memory Assessment Scales. Scores were divided into primacy (first four words), middle (middle four words), and recency (final four words) scores for all trials. For list acquisition, mixed effects modeling examined the main effects of and interactions between learning slope (logarithmic), age group, and serial position. Rate of learning increased logarithmically over four trials and varied by serial position, with growth of middle and recency word acquisition increasing more rapidly than recall of primacy words; this interaction did not differ by age group. Delayed retention differed according to age group and serial position; both older and younger adults demonstrated similar retention for primacy words, but older adults showed reduced retention for middle and recency words. Although older adults acquired less information across learning trials, the reason for this reduced acquisition was related to initial learning, not to rate of learning over time. Older compared to younger adults were less efficient at transferring middle and recency words from short-term to long-term memory.
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