Biomedical subjects
Publications and source records attributed to L W Poon.
This article outlines the reasons that detection of subtle changes in the cognitive system is difficult in geriatric assessment. A new assessment approach is introduced that examines cognitive patterns and facilitates the evaluation of subtle changes.
Stereotypical views of the elderly hold that very old persons are less adaptable to change and less comfortable handling crisis situations. Over the last five years, we have had the privilege of meeting 96 people aged 100 years or older as part of the National Institute of Mental Health (NIMH) funded, Georgia Centenarian Study (R01 MH 43435-05). We have encountered optimistic, wise individuals very engaged in living. Our research team continues to be amazed at the quality of life and the individual differences amongst centenarians.
This paper addresses the questions of whether depression compromises cognition in the elderly and whether discernable patterns of cognitive performances could be differentiated between patients with severe depression and those with organic dementia. Published data on geriatric depression and cognitive functioning are divided in demonstrating a depression effect. Further examination and external validation by new data show that the depression effect on discrete cognitive tasks is (1) small, and (2) sensitive to the confounding of sampling and task variables. Future research must take these factors into account. Patterns of cognitive functioning in depression and dementia are different and can be differentiated using a variety of measures. This review finds the term pseudodementia inappropriate and misleading and recommends that it be abandoned.
This paper compares older adults in their sixties, eighties, and 100s on personality, experience of life events, and coping. A secondary goal was to test a structural model of adaptation. Participants (165) filled out a personality inventory, life-event lists, and coping and mental health measures. Results revealed differences in personality: centenarians scored higher on dominance, suspiciousness, and imagination. While centenarians scored lower on active behavioral coping than other age groups, they used cognitive strategies when coping with health and family events. Results from the structural equation model indicated that extraversion and anxiety predicted morale and mental health.
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This study compares the dietary patterns of centenarians (n = 24) with elderly adults in their sixties (n = 54) and eighties (n = 47). Compared to the younger cohorts, centenarians consumed breakfast more regularly, avoided weight loss diets and large fluctuations in body weight, consumed slightly more vegetables, and relied on their doctor and family more than on the news media for nutrition information. On the other hand, centenarians were less likely to consume diets low in fat and to comply with nutritional guidelines designed to reduce the risk of chronic disease. Elderly black men consumed diets higher in sweets and fat compared to black women and white men and women. Nearly three times as many blacks expressed the desire to eat more nutritiously. High nutrition risks, particularly in blacks, were associated with lower physical and mental health and impaired activities of daily living.
Previous research has yielded mixed results with respect to the relationship between religiosity and adaptation in older adults. Most studies show that religiosity is stable over the life span, but that religiosity may or may not be related to such factors as physical and mental health, life satisfaction, and coping. This study adds to earlier investigations by including centenarians among the sample. The preliminary results of this research project support earlier findings that religiosity does not change significantly as one ages, although there is a trend in the results that suggests otherwise. The results also indicate a significant relationship between religiosity and physical health but no significant relationship between religiosity and mental health and life satisfaction. Religiosity and coping are strongly related, and there is the suggestion that religious coping mechanisms might be more important in the oldest-old.
In the Georgia Centenarian Study, cognitive resources were estimated by fluid and crystallized intelligence, acquisition and retrieval of new information, retrieval of familiar information, and problem-solving ability in community-dwelling and nondemented adults ranging from sixty to one hundred plus years of age. Five clusters of results were found: 1) cognitive performances were lower for the older cohorts; 2) when cognitive activities were dependent on everyday experiences, no age-related problem-solving decline was found; 3) physical health and mental health can significantly influence cognitive performances; 4) cognitive and personality factors can combine to account for a larger amount of adaptation variance than can be accounted for by either of the factors alone; and 5) individuals with a high level of intelligence and affect sustain their instrumental activities of daily living. Cognitive resources were an important contributor to successful adaptation for the oldest-old.
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A model of cognitive slowing is proposed with the following assumption: Information is lost during processing, processing occurs in discrete steps with step duration inversely related to the amount of information currently available, and the effect of aging is to increase the proportion of information lost per step. This model correctly predicts a positively accelerated relation between latencies of older and younger adults and provides a unified account of the effects of task complexity, practice, speed-accuracy tradeoffs, and fluctuations in individual performance. Strong support for the thesis that cognitive slowing is global, and not localized in specific age-sensitive components, is provided by the fact that the model accurately predicts the latencies of older adults on the basis of those of younger adults, without regard to the nature of the task, across a latency range of nearly 2 orders of magnitude.
We conducted a study to determine the effects of presenting prescription information in a pictorial compared to a verbal format on comprehension and memory in young and old adults. Both comprehension and memory for drug information were studied as a function of age and presentation method. Participants received prescription instructions on actual medicine bottles in one of two formats: verbal instructions only, or verbal instructions mixed with pictorial representations. Results indicated that (a) younger adults' memory for prescription information was facilitated by the mixed instructions, but that mixed instructions appeared to hamper older adults' memory for prescription information; (b) younger adults recalled more information overall relative to older adults across both presentation conditions; and (c) older adults were less able to comprehend prescription information relative to younger adults. Results suggest that well-organized verbal prescription labels are more facilitative for the elderly and that additional efforts must be undertaken to improve the clarity of labeling on prescription drugs.
The relationship between aspects of knowledge about memory and immediate and delayed recall on prose and word-list tasks was examined. Ss were 100 young and 100 older adults. Vocabulary ability was screened. Memory knowledge was assessed by the Metamemory in Adulthood (MIA) scale and the Short Inventory of Memory Experiences (SIME). Capacity and change measures of the MIA correlated with most dimensions of the SIME for both age groups. The anxiety measure of the MIA correlated with SIME measures only for the young. Regression analyses showed that strategy (MIA) predicted performance only for young adults, change (MIA) predicted performance only for older adults, and capacity (MIA) predicted performance for both age groups. Metamemory variables accounted for equivalent amounts of variance in both prose and word-list tasks, although there was an indication that prediction was slightly better for prose. Future researchers need to address the apparent increase in affect-related predictors of memory performance.
We examined both comprehension of and memory for information on prescription labels as a function of age, memory load, and study time across three experiments with young and old adults. We found that older adults consistently manifested poorer recall of prescription information than young adults; age effects occurred even when participants received unlimited study time; and both young and old adults had substantial difficulty comprehending drug information as it is presented from a pharmacy.
Two independent data sets were selected to examine the interrelations among reaction time (RT), between-subject variability or diversity (SD), and age. In both data sets, a strong correlation between RT and SD was obtained. This strong correlation was not affected when age was controlled in a partial correlation analysis. On the other hand, a weaker but significant correlation was obtained between age and SD. This correlation was eliminated when RT was controlled in a partial correlation analysis. Our analyses of the two data sets also indicated that the relation between RT and SD is identical for both young and elderly groups. Thus, the greater diversity often observed in performances of older groups is a direct consequence of slowing, rather than an independent effect of advancing age.
The present experiment demonstrates greater priming effects in a lexical decision task for older adults than for younger adults. Thirty-six older adults and thirty-six younger adults participated in a lexical decision experiment in which primes were category names and related targets were category exemplars that varied in category dominance. This manipulation of category dominance was intended to limit the predictability of target words based on prime words. Results showed that older adults had significantly greater priming effects than did younger adults. This outcome represents a departure from most studies of age effects on priming in lexical decision. It is suggested that older adults make greater use of context than younger adults when the context is of limited predictive value.
Speech processing involves rapid decoding and construction of meaning from a transitory acoustic signal. Because older adults have been found to be slower in performing many cognitive tasks, we hypothesized that they may have difficulty in immediate recall for speech of increasing input rate. Two experiments are reported in which both older and younger participants listened to and immediately recalled sentences that were systematically varied in speech rate and number of propositions. Although recall performance of the older adults showed a disproportionate decline when speech rate was increased, older adults, as well as the younger adults, were able to recall sentences of increasing propositional densities. We also found that the tendency to recall a greater proportion of main ideas than details (the levels effect) was enhanced by increased propositional density, and depressed by increased speech rate and increased age. These results are discussed in terms of an age-related change in the rate at which information can be processed in working memory.
Three studies were carried out to investigate orthographic and semantic priming effects in word retrieval. In this paradigm a prime is presented prior to the definition of a target word. The task is to produce the target word. We view the process of word retrieval as requiring access from a conceptually organized semantic network to an orthographically and phonemically organized lexical network. Primes that were orthographically (and phonemically) related to the target words were found to facilitate word retrieval. Both semantically related and unrelated primes inhibited word retrieval. Inhibition from both of these sources is attributed in part to the orthographic unrelatedness of these primes. This explanation is shown to be consistent with data from several other word retrieval studies (Brown, 1979; Roediger, Neely, & Blaxton, 1983). The word retrieval task is contrasted with the lexical decision task. It is suggested that the differential effects of orthographic and semantic priming in word retrieval and lexical decision are due to differences in retrieval processing between the two tasks.
Twenty-four young and 24 old adults participated in a lexical decision task (Study 1) in which they judged whether letter strings were words. No age differences were found in either accuracy or response latency. In Study 2 18 young and 18 old adults participated in a word retrieval study in which the stimulus was the definition of a target word and the task was to name the word that was defined. Younger adults were superior in word retrieval as measured by both number of successful retrievals and response latency. The discrepancy between the two sets of results is attributed to differences in retrieval requirements, which are interpreted within the framework of a two-component model of semantic memory. It is suggested that older adults have a specific deficit in accessing word-name information in an orthographically organized lexical network given stimulus information that is conceptual rather than orthographic.