David A. Grayson

Gait slowing as a predictor of incident dementia: 6-year longitudinal data from the Sydney Older Persons Study

Current definitions for the preclinical phase of dementia focus predominantly on cognitive measures, with particular emphasis on memory and the prediction of Alzheimers disease. Incorporation of non-cognitive, clinical markers into preclinical definitions may improve their predictive power. The Sydney Older Persons Study examined 6-year outcomes of 630 community-dwelling participants aged 75 or over at recruitment. At baseline, participants were defined as demented, cognitively intact or having a syndrome possibly representing the preclinical phase of Alzheimers disease, vascular dementia, an extrapyramidal dementia or various combinations of the three. Those with cognitive impairment in combination with gait and motor slowing were the most likely to dement over the 6-year period (OR 5.6; 95% CI 2.5-12.6). This group was also the most likely to die (OR 3.3; 95% CI 1.6-6.9). White matter indices on MRI scanning were not consistently correlated with gait abnormalities. Simple measures of gait may provide useful clinical tools, assisting in the prediction of dementia. However, the underlying nature of these deficits is not yet known.

Health habits and risk of cognitive impairment and dementia in old age: a prospective study on the effects of exercise, smoking and alcohol consumption.

Previous research has yielded inconsistent results on the effects of exercise, smoking and alcohol use on cognitive impairment and dementia in old age. We analysed data from the Sydney Older Persons Study to see if these health habits were associated with cognitive functioning, dementia or Alzheimers disease. Health habits were assessed in Wave 1 of the study, when the subjects were aged 75 years or over. Three years later, the subjects were tested for cognitive functioning and clinically examined for dementia and Alzheimers disease. The analysis was restricted to the 327 subjects examined in Wave 2 who were non‐demented in Wave 1. There were few significant associations between health habits and cognitive performance and these were not found consistently across cognitive measures. No associations were found with dementia or Alzheimers disease. While these health habits do not affect risk for dementia and cognitive impairment in the very elderly, who are at highest risk for these disorders, we cannot discount a role at younger ages.

Long-term benzodiazepine use by elderly people living in the community.

Objective : To investigate the prevalence of long‐term benzodiazepine use in an elderly community sample, and factors associated with such use.

Vascular risk factors, cognition and dementia incidence over 6 years in the Sydney Older Persons Study.

The specific contributions of factors associated with an increased risk of stroke to cognitive decline and vascular dementia in elderly people remain somewhat unclear. We investigated the prevalence of vascular risk factors (RFs) and their role on the incidence of dementia, cognitive decline and death over a 6-year period in a sample of 377 non-demented community dwellers aged 75 years and over at the time of study entry. Presence and history of vascular RFs and cognitive decline over 6 years were ascertained using direct interviews, medical and cognitive examinations. Hypertension and history of heart disease were very common affecting about 50% of the participants. At 6 years, 114 (30%) participants had died, and 63 (16.7%) met diagnostic criteria for dementia. Hypertension was significantly associated with a greater cognitive decline but not with dementia. Smoking and stroke diagnosis showed a significant positive association with death. Reported hypercholesterolaemia was found to be associated with a protective effect for the development of dementia, for cognitive decline and for death over the 6-year period. All other associations were non-significant. Figures of dementia incidence are similar to previous studies in contrast to the lack of anticipated effects of the vascular RFs. The results indicate that in very old participants, the impact of vascular RFs changes with time and may no longer contribute to the development of dementia and cognitive decline.

Longitudinal stability of latent means and individual differences: A unified approach

We examined the stability of responses to a multi‐item self‐esteem scale collected on five occasions over an 8‐year period. A wide variety of approaches were critically examined that considered the stability of means, individual differences (i.e., test‐retest correlations), and factor structures using traditional approaches (e.g., ANOVA and correlations) and structural equation models. Structural equation models based on multiple indicators provided a unified analytic approach for evaluating different aspects of stability and offered important advantages over traditional approaches. We describe a hierarchy of invariances and the nature of interpretations that are justified by different patterns of factor structure invariance associated with each level. We conclude that the assumptions underlying the typical repeated‐measures ANOVA approach to testing mean differences in longitudinal data are far more restrictive, less easily tested, and less likely to be met than those in the structural equation modeling ...

Informant-based staging of dementia using the clinical dementia rating.

The staging of dementia is ideally based on both an examination of the patient and a history taken from an informant. However, in some circumstances, only an informant history is possible. The aim of this study was to assess the validity of the Clinical Dementia Rating (CDR) when the rating is based solely on informant data. The CDR was used in a study of 360 persons aged 78 or older who were participants in a community survey, the Sydney Older Persons Study. The CDR was completed in two ways: (1) a social scientist made the ratings based on an informant interview; and (2) a physician made the ratings after an examination of the subject. All CDRs were scored in the conventional way, as well as by the revised method proposed by Gelb and St. Laurent (Alzheimer Dis Assoc Disord 1993;4:202-11). The informant CDR showed moderate agreement with the clinician CDR, showing that it would be a valid substitute in situations in which the subject could not be examined. The revised scoring method was slightly easier to implement than the conventional method.

Longitudinal confirmatory factor analysis: Common, time‐specific, item‐specific, and residual‐error components of variance

Following Cronbach (1970) and others, it is useful to decompose test score variation into common factor, time‐specific, item‐specific, and residual components. In the traditional approach to factor analysis, only two sources of variance can be estimated: common factor variance and a uniqueness term that confounds specific sources of variation and residual error. When the same items are measured on different occasions, however, it is possible to separate specific variance and residual error. Two approaches, the first‐order approach described by Raffalovich and Bohrnstedt (1987) and a second‐order approach based on Joreskog and Sorbom (1989; Joreskog, 1974) are considered initially. The two approaches, although based on different rationales, both suffer a similar weakness in that two of the four sources of variance are confounded. In the Raffalovich and Bohrnstedt approach, time‐specific variance is confounded with common factor variance that generalizes across items and time. In the second‐order approach b...

Public/Catholic Differences in the High School and Beyond Data: A Multigroup Structural Equation Modeling Approach to Testing Mean Differences

Previous research based on the large, nationally representative High School and Beyond (HSB) study has compared senior year achievement test scores for public and Catholic high school students after controlling for background variables and sophomore year test scores. These analyses, however, were based on traditional applications of multiple regression with its implausible assumptions that variables are measured without error and that residuals are uncorrelated. The present study demonstrates tests for mean differences on latent constructs using the LISREL approach to multigroup structural equation modeling (SEM) for this substantively important issue. Public/Catholic differences, even after controlling for background and sophomore outcomes, favored Catholic high school students on senior year outcomes (achievement, educational aspirations, and academic course selection) and subsequent college attendance. These public/Catholic differences were similar for students differing in race, SES (social economic status), and initial ability. Public/Catholic differences in achievement, educational aspirations, and college attendance were, however, apparently mediated by the academic orientation of course selection. The flexibility and advantages—but also the limitations—of this multigroup SEM approach are discussed.

Preclinical syndromes predict dementia: the Sydney older persons study

OBJECTIVES To identify if preclinical syndromes for Alzheimers disease, vascular dementia, and Parkinsons disease and related dementias exist. Identification of dementia at early or even preclinical stages has important implications for treatment. METHODS A community dwelling sample of 647 subjects aged 75 and over at recruitment were followed up for a mean period of 3.19 years (range 2.61 to 4.51 years). Each subject was asked to participate in a medical assessment which included a standardised medical history examining both past and current health and medication usage; a neuropsychological battery (mini mental state examination, Reid memory test, verbal fluency, subsets of the Boston naming test and similarities, clock drawing and copied drawings) and physical examination. Preclinical syndromes for the three predominant dementias (Alzheimers disease, vascular dementia and Parkinsons disease, and related dementias) and their combinations were defined using cognitive, motor, and vascular features. Their longitudinal outcome as defined by death and dementia incidence was examined. RESULTS Preclinical syndromes affected 55.7% (n=299) of subjects. Preclinical syndromes showed a trend for an increased odds of death (odds ratio 1.72, p=0.056) and a significantly increased odds of developing dementia (odds ratio 4.81, p<0.001). Preclinical syndromes were highly sensitive, detecting 52 of 58 (89.7%) incident dementias. Two hundred and sixteen of 268 (80.6%) preclinical subjects did not show dementia over the 3 year period (positive predictive value 19.4%). Subjects defined as having a combination of cognitive, extrapyramidal, and vascular features were at greatest risk of progressing to dementia. CONCLUSIONS Preclinical syndromes were sensitive and significant predictors of dementia. In view of their poor positive predictive value, the preclinical syndromes as defined in this study remain a research tool needing both definitional refinement and greater periods of observation. Multiple coexistent preclinical disorders resulted in a greater incidence of dementia, providing evidence for an additive role between multiple disorders.

Subcortical Vascular Disease and Functional Decline: A 6‐Year Predictor Study

OBJECTIVES: To identify predictors of activity of daily living (ADL) and instrumental activity of daily living (IADL) decline in a population with subcortical vascular dementia (SVD) and to evaluate potential mechanism of decline.