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Biomedical subjects

P Rabbitt

Publications and source records attributed to P Rabbitt.

At least 19 recordsLinked to original sources
PubMed1998

Long-term postoperative cognitive dysfunction in the elderly ISPOCD1 study. ISPOCD investigators. International Study of Post-Operative Cognitive Dysfunction.

BACKGROUND: Long-term postoperative cognitive dysfunction may occur in the elderly. Age may be a risk factor and hypoxaemia and arterial hypotension causative factors. We investigated these hypotheses in an international multicentre study. METHODS: 1218 patients aged at least 60 years completed neuropsychological tests before and 1 week and 3 months after major non-cardiac surgery. We measured oxygen saturation by continuous pulse oximetry before surgery and throughout the day of and the first 3 nights after surgery. We recorded blood pressure every 3 min by oscillometry during the operation and every 15-30 min for the rest of that day and night. We identified postoperative cognitive dysfunction with neuropsychological tests compared with controls recruited from the UK (n=176) and the same countries as study centres (n=145). FINDINGS: Postoperative cognitive dysfunction was present in 266 (25.8% [95% CI 23.1-28.5]) of patients 1 week after surgery and in 94 (9.9% [8.1-12.0]) 3 months after surgery, compared with 3.4% and 2.8%, respectively, of UK controls (p<0.0001 and p=0.0037, respectively). Increasing age and duration of anaesthesia, little education, a second operation, postoperative infections, and respiratory complications were risk factors for early postoperative cognitive dysfunction, but only age was a risk factor for late postoperative cognitive dysfunction. Hypoxaemia and hypotension were not significant risk factors at any time. INTERPRETATION: Our findings have implications for studies of the causes of cognitive decline and, in clinical practice, for the information given to patients before surgery.

Abdomen↗
PubMed1998

Test/re-test reliability of the CANTAB and ISPOCD neuropsychological batteries: theoretical and practical issues. Cambridge Neuropsychological Test Automated Battery. International Study of Post-Operative Cognitive Dysfunction.

Neuropsychological test batteries are repeatedly administered to evaluate changes over time or the effects of clinical interventions. Relationships between scores on different tests within batteries are also examined to test models for associations between functional deficits. These comparisons may be misleading unless Test/Re-test reliability for individual tests is satisfactory. Interpretations of repeated measurements also depend on the extent to which improvement with practice varies between tasks and between more and less able individuals. Test/Re-test correlations and practice effects for two neuropsychological test batteries (CANTAB, ISPOCD) and from laboratory tasks commonly used in cognitive assessments of older people were obtained from large groups of healthy elderly. Tests in neuropsychological batteries varied markedly in test/re-test reliability which, in some cases, fell below levels considered methodologically acceptable. Putative measures of 'frontal' or 'executive' function, in which performance may be markedly improved by abrupt discovery of an appropriate strategy, were especially likely to show low reliability. Most tests showed significant practice effects, and on some these are substantial enough to compromise comparisons on repeated testing. On a minority of tests practice effects were counter-intuitive, in that less able showed significantly more gains than more able individuals.

Aged↗
PubMed1998

The effects of age upon some aspects of lifestyle and implications for studies on circadian rhythmicity.

BACKGROUND: Most studies on lifestyle changes in old age have been transverse. We have conducted a longitudinal study. SUBJECTS: 112 non-institutionalized subjects were studied in 1984 and again 10 years later (ages in 1984 ranged from 53-82 years). PROTOCOL: On each occasion subjects recorded in a diary their times of retiring and rising and of taking meals, during a 'typical week'. They also recorded whether they lived alone or with somebody. ANALYSIS: The diaries were scored to establish any effects of age or living alone on the timing and variability of their lifestyle. RESULTS: Age was associated with changes in the sleep/wake schedule and mealtimes and a decrease of daily variation in these variables. When these changes were compared in subjects living alone and with somebody, the increase in time spent in bed and the decreases in variability of times of rising and meals were more marked in subjects living with somebody. CONCLUSIONS: A deteriorating body clock contributes to some of these changes, but an increasingly inflexible lifestyle will offset some of the effects of this decline in circadian rhythmicity.

Activities of Daily Living↗
PubMed1997

The Alan Welford Memorial Lecture. Ageing and human skill: a 40th anniversary.

Even 40 years after it was published, a re-reading of Alan Welford's seminal book, Ageing and Human Skill, offers important and curiously neglected ideas. In particular, it shows that current 'single factor' models for cognitive ageing, and for general intellectual abilities neglect the complexity of even apparently very simple tasks; that older individuals can be impressively good at acquiring new skills; that the performance of older people on novel tasks is different from that of young adults not only in quantitative terms, because they are slower and less accurate, but also qualitatively, in ways similar to individuals who have suffered damage to the frontal lobes of their brains. We celebrate Alan's prescience in being the first to clearly raise these issues, and to discuss elegant but sadly neglected experimental paradigms and techniques of analysis that allow them to be explored.

Adult↗
PubMed1995

Unique and interactive effects of depression, age, socioeconomic advantage, and gender on cognitive performance of normal healthy older people.

A sample of 4,243 residents of Manchester, England and Newcastle-upon-Tyne, England, aged 50 to 93 years, completed the Beck Depression Scale (A.T. Beck, C.H. Ward, M. Mendelson, J. Mock, & J. Erbaugh, 1961) and a battery of 6 different cognitive tests. Beck scores were low, indicating gradations of dysphoria rather than clinical depression. Beck scores did not vary with age but were significantly higher for women than for men and for disadvantaged than for advantaged socioeconomic groups. Measures of fluid, but not of crystallized, ability declined as age increased. Socioeconomic disadvantage was associated with poorer performance on all cognitive tests. Men scored higher on a test of spatial reasoning, and women scored higher on a test of word definition and on 2 tests of verbal memory and learning. However, after variance associated with all these demographic and individual-difference variables was considered, and within a range indicative of dysphoria rather than clinical depression, higher Beck scores were associated with significantly poorer performance on both crystallized and fluid measures of cognitive ability. This association was less marked in women than in men, but age, socioeconomic advantage, and estimated lifetime intellectual ability did not act as protective or risk factors for vulnerability of cognitive processes to dysphoria.

Age Factors↗
PubMed1994

Age, information processing speed, and intelligence.

Two parallel, but independent, literatures have grown out of observations that individual differences in information processing speed, as expressed in performance on choice reaction time (C RT) tasks, modestly correlate with individual differences in age and IQ test performance. These associations have prompted theories that individual differences in information processing speed functionally determine individual differences in performance of all cognitive skills by people of different general intellectual ability (Eysenck, 1986; Jensen, 1985) or age (Salthouse, 1982, 1985). The experiments on which this literature has been based suffer from methodological weaknesses, such that comparisons have only been made very early in practice and have only concerned mean latencies for correct responses. An experiment compared 90 volunteers aged from 50 through 79 years who were grouped in terms of their performance on the AH 4 (Heim, 1968) IQ test. It explored the joint and independent effects of individual differences in age and in IQ test score and the effects of practice on mean latencies (C RTs) on the shapes of distributions of correct and incorrect responses and on the limiting speeds with which accurate responses can be made (speed/error trade-off functions). We suggest that a plausible explanation for the results is that individual differences in age and in general ability influence C RTs mainly because they affect the efficiency with which responses can be controlled to maximize speed while maintaining accuracy.

Age Factors↗
PubMed1994

Minor head injury: pathophysiological or iatrogenic sequelae?

This study addresses the possibility that cognitive sequelae--albeit of a transient or minor character--can be associated with mild head injury. Twenty men (aged 16-30 years of age), whose post-traumatic amnesia did not exceed eight hours, were examined within 48 hours of their accident and again one month later. This unselected sample had no previous history of head injury. A control group of 20 men of similar socioeconomic background, was selected from medical wards (where they had been admitted for orthopaedic treatment or a minor operation). They were also retested one month after the first examination. Neuropsychological tests were selected to measure abilities often compromised after significant head injury, namely memory and attention. The experimental component consisted of the fractionation of a complex skill (paced addition) to probe for deficits at different stages of information processing: perception and input into storage; search for and retrieval of information from working memory; and paced and unpaced addition. In general, no significant difference was found between the experimental and control groups, with the possible exception of an initial decrement on two working memory tasks: probe digits and a keeping track task (where the subject has to keep in mind and update a number of variables at the same time). The keeping track paradigm, ostensibly of ecological relevance, may well be worth further exploration in memory research, and in studies of more severely head-injured patients. It is further suggested that the appropriate management and counselling of mildly head-injured patients may help to avert symptoms that are of psychological rather than pathophysiological origin.

Adolescent↗
PubMed1993

Does it all go together when it goes? The Nineteenth Bartlett Memorial Lecture.

As groups of people age, the differences in the cognitive abilities of the most and least able become more extreme. This increase in between-individual variance is accompanied by an increase in within-individual variance: the difference between individuals' levels of performance on their best and least well retained skills. The implications of increasing between-individual variance are discussed in terms of the range of different factors that may affect cognitive ageing. Increases in within-individual variance are discussed in terms of differences between "fluid" and "crystallized" abilities. The usefulness of this distinction and its functional implications are questioned. The hypothesis that age-related declines in "fluid" abilities are best modelled in terms of declines in a single factor is evaluated. Evidence is presented of disparate rates of decline, even of "fluid" cognitive abilities, such as performance on IQ tests, ability on information-processing tasks, and efficiency on memory tasks. Data from large-scale cross-sectional studies suggests that cognitive skills do not "all go together when they go," but that there may rather, be characteristic patterns, or syndromes, of cognitive ageing.

Adult↗
PubMed1991

Do older people know how good they are?

Information and procedures that have been overlearned during a lifetime form a body of 'crystallized' intelligence that is relatively unaffected by ageing. Thus in spite of marked decrements in their 'fluid' memory abilities it is possible that older people may retain knowledge about the limitations and characteristics of their own memory ('metamemory'). To test whether efficiency of metamemory is, indeed, independent of age-related decline in fluid intelligence, 320 people aged from 50 to 79 years were asked to predict their probable performance on four simple memory tasks which had been carefully explained to them. They then experienced the tasks and their predictions were compared with their actual performances. Actual task performance was modestly predicted by chronological age and by AH 4 and Mill Hill IQ test scores but not by subjective self-ratings of everyday memory and cognitive efficiency (the Broadbent CFQ, and the Sunderland & Harris MQ). The data suggest that absolute levels of prediction of performance were associated with self-confidence and were best predicted by scores on the Beck depression scale and by fluid IQ test scores. There was also evidence that individuals with higher test scores gave more accurate as well as more optimistic predictions of their own abilities. Taken together these results suggest that the accuracy of individuals' assessments of their own abilities does alter with age-related changes in fluid IQ, but probably more radically by age-related changes in self-regard and in life-style.

Activities of Daily Living↗
PubMed1990

'Lost and found': some logical and methodological limitations of self-report questionnaires as tools to study cognitive ageing.

Laboratory tests show a decline in memory efficiency with age, but may not reflect highly practiced everyday memory skills. Self-rating questionnaires probe memory efficiency in everyday life, but seven logical and methodological problems ambiguate interpretation of the data they yield. To explore these problems, 442 volunteers aged from 50 to 85 years were given the AH 4 IQ tests, Mill Hill Vocabulary Tests, Beck Depression Inventory (BDI), Broadbent Cognitive Failures Questionnaire (CFQ), Sunderland & Harris Memory Failure Questionnaire (MFQ), the 'Lost and Found' Questionnaire (LF, a new domain-specific probe of the variety, frequency and aetiologies of losses of possessions) and two laboratory memory tests. All self-rating questionnaire scores correlated modestly with each other. Counter-intuitively, individuals over 60 years old reported fewer lapses on the LF and on the CFQ. No SRQ scores correlated with performance on laboratory tasks. CFQ scores did not correlate with IQ test scores but high IQ test scorers reported greater recent decline in memory efficiency (MFQ) and greater current frequency of losses of objects (LF). CFQ and LF scores correlated positively with Beck Depression Inventory scores, suggesting some common loading for poor self-regard. The results suggest that subjective self-ratings cannot reflect absolute levels of everyday competence, but only the relative success of individuals' adaptations to idiosyncratic environments which, as they age, may change faster than their abilities. However, besides exposing the limitations of self-report techniques, these analyses also suggest practical ways of adapting and using SRQs which may allow us to gain better insights into changes and individual differences in functional efficiency in everyday life.

Aged↗
PubMed1990

Mild hearing loss can cause apparent memory failures which increase with age and reduce with IQ.

Rabbit (1968) tested the accuracy with which young adults with excellent hearing could repeat lists of numbers, words or continuous text which they heard over a system which maintained a constant ratio of white noise to speech signal irrespective of signal strength. Noise levels which allowed individual subjects correctly to repeat every word as they heard it (i.e. shadow without errors) nevertheless reduced their ability to remember what they had heard. This appeared to be because increased effort necessary to recognise words through low levels of noise prevented adequate rehearsal or elaborative encoding of material to be remembered. This finding that slight degradation of sensory input had secondary consequences on memory and comprehension of spoken material led to an interpretation of findings that 960 individuals aged from 50 to 82 years, in contrast to young adults, showed markedly better recall for word lists presented visually than for word lists presented auditorally, even when each word in each list was correctly read or repeated aloud. Audiometric screening of a sub-set of this population allowed 30 individuals with mild hearing losses (35 to 50 db) in each of the three age-decades 50 to 59, 60 to 69 and 70 to 79 years to be compared with matched controls who had pure-tone hearing losses of less than 35 db on memory for lists of 30 words presented visually or over a good-quality sound system. In both presentation modes lists were only scored if all words were correctly read or repeated. Individuals with slight hearing loss recalled visually presented words as well, but recalled auditorally presented words significantly less well, than their controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Do clever old people have earlier and richer first memories?

In a study of 377 people, from 54 to 83 years old, it was shown that the age of earliest memories was unrelated to current age but was related to intelligence. People with high IQ test scores remembered first and second memories at an earlier age than did those with lower IQ test scores. Intervals between first and second memories were briefer for those with high scores. The content of early memories was unrelated to age or intelligence.

Aged↗
PubMed1980

Selective anticipation for events in old age.

When considering how momentary variations in attentional selectivity occur it is useful to distinguish between situations in which selectivity is controlled by external events (data-driven control) and other situations in which people use their previous experience to actively adjust their attentional selectivity from moment to moment (memory-driven control). In terms of this distinction Experiment 1 suggests that elderly people show preservation, or even enhancement, of data-driven control but loss of memory-driven control of selective attention. A general conclusion is that as people grow older they become more labile, and more subject to control by external events. Experiment 2 suggests that one possible reason may be that old subjects remember, analyse, and employ smaller samples of the recent past when they are computing what is most likely to happen next.

Adolescent↗