Biomedical subjects

Scott M Hofer

Publications and source records attributed to Scott M Hofer.

At least 19 recordsLinked to original sources

PubMed2006

Psychopathology in young people with intellectual disability.

CONTEXT: Comorbid severe mental health problems complicating intellectual disability are a common and costly public health problem. Although these problems are known to begin in early childhood, little is known of how they evolve over time or whether they continue into adulthood. OBJECTIVE: To study the course of psychopathology in a representative population of children and adolescents with intellectual disability. DESIGN, SETTING, AND PARTICIPANTS: The participants of the Australian Child to Adult Development Study, an epidemiological cohort of 578 children and adolescents recruited in 1991 from health, education, and family agencies that provided services to children with intellectual disability aged 5 to 19.5 years in 6 rural and urban census regions in Australia, were followed up for 14 years with 4 time waves of data collection. Data were obtained from 507 participants, with 84% of wave 1 (1991-1992) participants being followed up at wave 4 (2002-2003). MAIN OUTCOME MEASURES: The Developmental Behaviour Checklist (DBC), a validated measure of psychopathology in young people with intellectual disability, completed by parents or other caregivers. Changes over time in the Total Behaviour Problem Score and 5 subscale scores of the DBC scores were modeled using growth curve analysis. RESULTS: High initial levels of behavioral and emotional disturbance decreased only slowly over time, remaining high into young adulthood, declining by 1.05 per year on the DBC Total Behaviour Problem Score. Overall severity of psychopathology was similar across mild to severe ranges of intellectual disability (with mean Total Behaviour Problem Scores of approximately 44). Psychopathology decreased more in boys than girls over time (boys starting with scores 2.61 points higher at baseline and ending with scores 2.57 points lower at wave 4), and more so in participants with mild intellectual disability compared with those with severe or profound intellectual disability who diverged from having scores 0.53 points lower at study commencement increasing to a difference of 6.98 points below severely affected children by wave 4. This trend was observed in each of the subscales, except the social-relating disturbance subscale, which increased over time. Prevalence of participants meeting criteria for major psychopathology or definite psychiatric disorder decreased from 41% at wave 1 to 31% at wave 4. Few of the participants (10%) with psychopathology received mental health interventions during the study period. CONCLUSION: These results provide evidence that the problem of psychopathology comorbid with intellectual disability is both substantial and persistent and suggest the need for effective mental health interventions.

Adolescent↗

PubMed2006

Intraindividual coupling of daily stress and cognition.

Most psychological theories predict associations among processes that transpire within individuals. However, these theories are often tested by examining relationships at the between-persons (BP) rather than the within-persons (WP) level. The authors examined the WP and BP relationships between daily stress and daily variability in cognitive performance. Daily stress and cognitive performance were assessed on 6 occasions in 108 older adults and 68 young adults. WP variability in stress predicted WP variability in response times (RTs) on a 2-back working memory task in both younger and older adults. That is, RTs were slower on high-stress days compared with low-stress days. There was evidence of an amplified WP stress effect in the older adults on a serial attention task. There was no evidence of stress effects on simple versions of these tasks that placed minimal demands on working memory. These results are consistent with theories that postulate that stress-related cognitive interference competes for attentional resources.

Activities of Daily Living↗

PubMed2006

Effects of repeated testing in a longitudinal age-homogeneous study of cognitive aging.

Estimates of gains related to repeated test exposure (retest effects) and within-person cognitive changes are confounded in most longitudinal studies because of the nonindependent time structures underlying both processes. Recently developed statistical approaches rely on between-person age differences to estimate effects of repeated testing. This study, however, demonstrates how retest effects can be evaluated at the group level in an age-homogeneous population-based study by use of a sampling-based design approach in which level and change of cognitive performance of previous participants, measured at ages 70, 75, 79, 81, 85, 88, 90, 92, 95, 97, and 99 years, were compared with performances of survivors of a representative sample identified and drawn from the same original population cohort but invited for the first time at age 85 with subsequent measurements at ages 88, 90, 92, 95, 97, and 99. The comparisons revealed a trend toward retest effects on two out of five cognitive measurements. The study demonstrates how a design-based approach can provide valuable insights into continuous learning processes embedded in population average aging trajectories that are not confounded with cohort and mortality-related selective attrition.

Aged↗

PubMed2005

Social context in gene-environment interactions: retrospect and prospect.

While many behavioral scientists believe that gene-environment (GE) interactions play an important and perhaps pervasive role in human development and aging, little attention has been devoted to a fundamental conceptual issue: What is it about social context that could alter gene expression? We draw on existing examples of GE interactions to formulate a typology that identifies a set of generic mechanisms by which E moderates G. Empirical studies suggest four ideal types: Social context can trigger a genetic diathesis, compensate for a genetic diathesis, act as a control to prevent behaviors for which there is a genetic predisposition, and enhance adaptation through proximal processes. This typology highlights several problems, however, with prior empirical research, which may explain, in part, why so few GE interactions have actually been observed. These problems include inattention to the dynamic nature of social experience, the manifold, often-intercorrelated dimensions of social context ("EE interactions"), mediators that link social context and the genotype, and analytic models that examine GE interactions as processes that characterize individual development. In turn, these insights call for the integration of life course sociology and behavioral genetics to foster ways of studying genes, context, and aging.

Aging↗

PubMed2004

Comorbid type 2 diabetes mellitus and hypertension exacerbates cognitive decline: evidence from a longitudinal study.

BACKGROUND: diabetes and hypertension are two highly prevalent diseases in the old population. They are highly related such that comorbidity is common. OBJECTIVES: to examine (i) the independent impact of the respective diseases on cognitive decline in very old age and (ii) the interactive impact of the two diseases on cognitive decline. SUBJECTS: 258 individuals (mean age = 83 years), all non-demented at baseline. Of these, 128 individuals (non-cases) were free from diabetes and hypertension, 92 individuals had a diagnosis of hypertension, 16 had a type 2 diabetes mellitus diagnosis without hypertension, and 22 had comorbid diabetes and hypertension. METHOD: a population-based longitudinal study of ageing (The OCTO-Twin Study), including four measurement occasions 2 years apart. The Mini-Mental State Examination was used to measure general cognitive function. Data were analysed using SAS Proc Mixed multilevel modelling. RESULTS: longitudinal trajectories indicated a steeper decline in cognitive function related to diabetes but not related to hypertension. However, the results indicated greatest cognitive decline among persons with comorbid diabetes and hypertension. CONCLUSIONS: it is concluded that comorbidity of diabetes and hypertension produce a pronounced cognitive decline. This finding emphasises the importance of prevention and treatment of those highly prevalent diseases in the old population.

Aged↗

PubMed2004

Type 2 diabetes mellitus contributes to cognitive decline in old age: a longitudinal population-based study.

We examined change in neuropsychological test performance related to type 2 diabetes mellitus across a 6-year interval. A population-based sample of 274 elderly participants (36 with diabetes and 238 without diabetes) was examined at four occasions at a 2-year interval. The participants were 80-93 years of age (M = 82.8 years) and without dementia at baseline. The test battery included tests of speed, visuospatial ability, short-term memory, semantic memory, episodic memory, and the Mini Mental Status Examination. Several models, taking into account diabetes and demographic data, were analyzed using SAS Proc Mixed multilevel modeling. At baseline, there were no significant differences in the neuropsychological tests related to diabetes. The longitudinal analyses, however, showed that diabetes was a significant predictor of decline for many of the tests. These findings points to the conclusion that type 2 diabetes is associated with accelerated cognitive decline in old age that may result in dementia.

Age Factors↗

PubMed2004

Change in cognitive capabilities in the oldest old: the effects of proximity to death in genetically related individuals over a 6-year period.

Change in cognitive abilities was assessed over a 6-year period in a sample of monozygotic and same-sex dizygotic twin pairs (N = 507 individuals), aged 80 and older (mean age = 83.3 years: SD = 3.1). who remained nondemented over the course of the study. Latent growth models (LGMs) show that chronological age and time to death are consistent predictors of decline in measures of memory, reasoning, speed, and verbal abilities. Multivariate LGM analysis resulted in weak and often negative correlations among rates of change between individuals within twin pairs, indicating greater differential change within twin pairs than occurs on average across twin pairs. These findings highlight several challenges for estimating genetic sources of variance in the context of compromised health and mortality-related change.

Aged↗

PubMed2004

Longitudinal designs, methods and analysis in psychiatric research.

OBJECTIVE: To outline the strengths and limitations of longitudinal research designs in psychiatry, and to describe different types of longitudinal designs and methods for analyzing longitudinal data. METHOD: Key references on longitudinal methods were reviewed and examples drawn from literature in psychiatry and psychology. RESULTS: Longitudinal studies provide important information regarding the incidence and developmental trajectories of mental disorders. They allow for identification of risk factors and developmental concomitants. Recent developments in statistical methods for analyzing longitudinal data provide efficient estimates of change and predictors of change over time, identification and characteristics of distinct subgroups defined by change pattern, and improved methods for obtaining unbiased population estimates when data are incomplete. CONCLUSION: Longitudinal designs, methods and analysis can contribute to psychiatric studies on risk factors for common mental disorders, studies of early intervention and prevention and treatment outcomes.

Humans↗

PubMed2003

The influence of mortality on twin models of change: addressing missingness through multiple imputation.

Twin analyses of phenotypes that are associated with mortality may provide biased heritability estimates if the models require that data from both members of a pair are available. This is particularly true when longitudinal analyses are applied to measures of cognition or biomarkers of aging. The effect of applying imputational techniques that include information on age at death was tested on longitudinal data from two twin studies of aging, each with up to four occasions of measurement. Measures of twin similarity for intercepts and slopes from three latent growth curve models were compared: without imputed data, including imputed data but without information on age at death, and including imputed data with information on age at death. Results indicated that twin similarity for slopes decreases when mortality is accounted for, but that considerable age-related covariation remains.

Humans↗

PubMed2003

Investigating age differences in the genetic and environmental structure of the tridimensional personality questionnaire in later adulthood.

In this study we examined cross-sectional age differences in means, phenotypic covariance structure, and the underlying genetic and environmental structure of four personality constructs from Cloninger's personality system: Novelty Seeking (NS), Harm Avoidance (HA), Reward Dependence (RD), and Persistence (PS). Study participants were same-sex female twins between the ages of 50 and 96, drawn from the American Association of Retired Persons (AARP) twin sample. We examined age differences by comparing younger (age 50-65) and older (age 661) cohorts (based on a median split of the sample) and by estimating biometrical model parameters as linear and quadratic functions of continuous age. Results indicated modest, but significant, mean-level declines across this age range for NS, RD, and PS. HA showed no significant mean differences. We found moderate heritability estimates for all of the TPQ higher-order personality dimensions, ranging from 0.16 to 0.62. No significant age differences in the proportion of genetic and environmental influences on the TPQ dimensions were found. For HA, RD, and PS there were no significant age-related differences in total variance. However, for NS we observed a decline in total phenotypic variance across age cohorts.

Age Factors↗

PubMed2003

Cross-sectional and longitudinal patterns of dedifferentiation in late-life cognitive and sensory function: the effects of age, ability, attrition, and occasion of measurement.

The dedifferentiation hypothesis is examined with respect to age-group differences, ability-group differences, attrition-group differences, and time. Cognitive and sensory data were analyzed from individuals (n = 1,823) who completed a clinical assessment on at least 1 of 3 occasions of measurement in the Australian Longitudinal Study of Ageing. Inconsistent dedifferentiation effects were associated with low ability and early attrition from the study, but age-related dedifferentiation was not found. Longitudinal analyses confirmed the cross-sectional analyses. Even though instances of dedifferentiation were identified between pairs of sensory and cognitive variables, consistent patterns of dedifferentiation were not found. These results do not support the view that shared biological factors become increasingly important for explaining within-individual change in cognitive and sensory function in later life.

Age Factors↗

PubMed2003

Evaluating the interdependence of aging-related changes in visual and auditory acuity, balance, and cognitive functioning.

High proportions of shared age-related variance are found among measures of perceptual acuity, balance, muscle strength, and cognitive capabilities in age-heterogeneous, cross-sectional studies. Reliance on cross-sectional studies is problematic, however, because associations may arise from age-related mean trends. Narrow age-cohort samples provide an alternative basis for testing hypotheses regarding associations among rates of change. Cross-domain associations were evaluated in combined 75-year-old cohort samples from Denmark, Finland, and Sweden. In general, no consistent associations were found across sensory, balance, strength, and cognitive domains. These findings indicate that the effects of aging on sensory acuity, balance, and cognitive functioning are likely to be largely independent, multidimensional, and complex at the level of the individual.

Age Factors↗

PubMed2003

Modeling memory decline in older adults: the importance of preclinical dementia, attrition, and chronological age.

This longitudinal study examined memory loss in a sample of 391 initially nondemented older adults. Analyses decomposed observed memory loss into decline associated with preclinical dementia, study attrition, terminal decline, and chronological age. Measuring memory as a function of only chronological age failed to provide an adequate representation of cognitive change. Disease progression accounted for virtually all of the memory loss in the 25% of the sample that developed diagnosable dementia. In the remainder of the sample, both chronological age and study attrition contributed to observed memory loss. These results suggest that much of memory loss in aging adults may be attributable to the progression of preclinical dementia and other nonnormative aging processes that are not captured by chronological age.

Aged↗

PubMed2003

Correlated and coupled cognitive change in older adults with and without preclinical dementia.

Common factor aging theories state that correlations among cognitive age effects signify a single underlying causal process. The logic underlying this proposition was evaluated by examining correlated cognitive change in a sample of 391 initially nondemented older adults who were tested annually for up to 16 years. Between-person correlations among rates of change (range = .56-.61) were partly attributable to model misspecification and the aggregation of heterogeneous groups of individuals. Correlated within-person cognitive change was much stronger in the cases (.45-.51) than in the noncases (.07-.18). These results demonstrate that correlated change may either signify causal commonality or the cumulative effects of multiple age-related conditions that can affect multiple cognitive systems.

Aged↗

PubMed2003

A latent growth curve analysis of late-life sensory and cognitive function over 8 years: evidence for specific and common factors underlying change.

Correlations among rates of change in sensory and cognitive functioning in adulthood were evaluated. Measures of Vision, Hearing, Memory, Speed and Verbal ability were obtained in 1992, 1994, and 2000 in the Australian Longitudinal Study of Aging (N = 2,087 at baseline). Data from 1,823 participants who undertook at least 1 clinical assessment were analyzed using latent growth curve models. A significant moderate-sized association between rates of change in Memory and Vision was found. This remained after statistically controlling for the effects of age, gender, education, self-rated health, medical conditions, and depressive symptoms. Rate of change in Hearing was weakly associated with rate of change in Memory. The results support a theory incorporating a major role for unique factors in addition to common factors underlying sensory and cognitive change in old age.

Aged↗

PubMed2002

Terminal decline and markers of cerebro- and cardiovascular disease: findings from a longitudinal study of the oldest old.

The purpose of this study was to examine the cognition-survival relationship among nondemented individuals in late life. The longitudinal design included three examinations at 2-year intervals. At baseline, 466 individuals (age range = 80-98) were examined. During the 6 years of follow-up, 206 individuals died. Four survival groups were defined on the basis of mortality prior to the subsequent measurement occasion. Tests of cognitive functioning encompassed the domains of crystallized knowledge, inductive reasoning, visuospatial ability, short-term memory, episodic memory, and speed. Significant associations were found between cognitive performance at baseline and subsequent survival. After adjusting for stroke and markers of cardiovascular disease, the authors found that only three out of six cognitive domains remained significant predictors of survival. The longitudinal analyses revealed limited evidence for an accelerated decline prior to death. The main results suggest that level of cognitive performance in late life is associated with proximity to death, that this relationship is longstanding, and that it is partially influenced by compromised cardio- and cerebrovascular functioning.

Aged↗

PubMed2002

Change in cognitive functioning associated with apoE genotype in a community sample of older adults.

The influence of a genetic risk factor, apolipoprotein E (apoE) epsilon4 variant, was assessed in older adults aged 70 to 94 on 3 occasions over 7 years. The results of latent growth curve analyses are reported for individuals genotyped for apoE at the 2nd measurement occasion (n = 601) and for a subsample of individuals without probable or definite dementia during the 1st or 2nd occasion (n = 434). ApoE-epsilon4 status was a significant predictor of level and change in memory performance and change in speed performance in the full sample, and of initial level and change in memory performance in the nondemented subsample. These results support previous findings that apoE-epsilon4 is associated with accelerated memory deterioration in individuals without clinical dementia.

Aged↗

PubMedDate not supplied

Intraindividual variability, change, and aging: conceptual and analytical issues.

BACKGROUND: Developmental researchers use a variety of research designs to examine aging-related changes. Most longitudinal studies of aging are based on research designs that feature successive, widely spaced, assessments to estimate changes in cognitive performance. Such designs assume that short-term variations in cognitive performance are small relative to long-term changes or have modeled such phenomena as nuisance parameters. OBJECTIVE: There is now sufficient empirical evidence to establish intraindividual cognitive variability as a systematic source of individual differences and of important predictive value for aging-relevant outcomes. METHODS: After an overview of types of change, potential underlying processes, and adequate analytic designs, we discuss consequences for lifespan aging research. RESULTS: We emphasize that interpretations of both cross-sectional and longitudinal results need to consider and specify theoretical assumptions about short-term and long-term changes. CONCLUSIONS: Above and beyond the analysis of long-term mean changes, short- term changes are an important aspect of aging-related change, and their analysis may help to explain psychological processes of adaptation.

Aging↗