Cognitive function in the Caerphilly study: associations with age social class, education and mood.

Baseline cognitive function was established for a study of pre-symptomatic cognitive decline in 1870 men from the general population aged 55-69 years as part of the third examination of the Caerphilly Study. Cognitive assessment included the AH4, a four choice serial reaction time task, a modified CAMCOG, MMSE, NART and various memory tests. Distributions and relationships with age, social class, education and mood at time of testing are presented for a younger population than has previously been available. Multiple linear regression showed cognitive function to be independently associated with all four factors. The age effect was equivalent to one half of a standard deviation (SD) in CRT and AH4 scores. Only the NART score was not associated with age, supporting the use of NART score as an estimate of pre-morbid IQ. The largest age adjusted differences between men with low and normal mood were for the AH4 (3 points, t = 5.6, p < 0.0001) and the CAMCOG (2 points, t = 5.8, p < 0.0001). The smallest age adjusted effect of mood was for the CRT (33 ms, t = 2.14, p = 0.32) and the MMSE (0.4 points, t = 2.97, p = 0.003). Age, mood and education adjusted social class effects were very large ranging between around 0.5 SD for the CRT, and 1.0 SD for the AH4 and NART, respectively. For educational status age, mood and social class adjusted differences were also substantial with tests for trend showing the largest differences for the NART (t = 12, p < 0.0001) and modified CAMCOG (t = 10.6, p < 0.0001) with the smallest differences for the CRT (t = 2.73, p = 0.006).

Decrements in cognitive performance in metal inert gas welders exposed to aluminium.

OBJECTIVES: Often little has been discovered of the cognitive functions affected by occupational toxins because many functions cooperate to produce the single performance scores typically reported from neuropsychological tests. To facilitate the interpretation of neuropsychological scores, the issue of occupational exposure to aluminium was examined with an approach intended to increase understanding of those cognitive processes that may be affected. METHODS: The investigation was a cross sectional study of asymptomatic aluminium welders and a reference group of mild steel welders. Based on urinary aluminium concentrations, welders were classified into a reference (n = 28), low (n = 27), and high (n = 24) exposure group. The mean urinary aluminium concentrations were 0.46, 2.25, and 9.98 mumol/l, respectively. A comprehensive neuropsychological examination was undertaken to assess psychomotor function, simple visual reaction time, attention related tasks, verbal and visual or visuospatial abilities as well as verbal and visual learning and memory. RESULTS: Aluminium welders showed no impairment on the finger tapping, Santa Ana dexterity, simple visual reaction times, any of the verbal memory tasks, the similarities subtest of Wechsler adult intelligence scale, or the Stroop task. However, the low exposed group performed poorer on the memory for designs and on more difficult block design items demanding preliminary visuospatial analysis. The time limited synonym task, embedded figures, digit symbol speed, and the backward counting component of the divided attention task showed exposure-response relations. CONCLUSIONS: The impairments found were circumscribed. When the neuropsychological tasks were scored to show some of the underlying theoretical cognitive structures, the results indicated that performance difficulties were mainly detected in tasks requiring working memory, particularly that relating to processing of visuospatial information. There was also evidence that such impairments are more readily found in time limited tasks involving visually presented material, in which effective visual scanning combined with control of working memory is demanded.

Cognitive neurotoxicology: a luxury or necessity?

Impaired psychological test performance is often observed at concentrations of a neurotoxicant below those producing harmful effects on other organ systems. The importance of this distinctive susceptibility lies in the opportunity it provides for the early detection of dysfunction. From this perspective, it is essential to evolve sensitive psychological methods for studying these states of marginal toxicity. It is argued that a cognitive approach provides the necessary degree of sensitivity and specificity for characterizing these states. Given the growing interest in using cognitive models to assess minor dysfunction in areas outside neurotoxicology, it is further argued that theoretically motivated methods can no longer be considered a luxury for neurotoxicological work. It is concluded that there are at least two advantages to this approach. First, it provides a theoretical framework for organising data. Second, establishing and developing links to substantive areas of cognitive investigation outside neurotoxicology will allow cross-fertilization to occur on a scientific level and provide a more convincing basis for action on a regulatory level.

Long-term cognitive sequelae of solvent intoxication.

Memory problems lasting 8 months have previously been described for a small group of female solvent workers following an accidental workplace solvent intoxication. Three years after the intoxication the presence of longer-term residual impairment of cognitive functions was evaluated. The major residual difficulty uncovered related to the speed of processing linguistic material, with workers showing slower verification on tasks probing syntactic and semantic reasoning within the context of relatively unimpaired response execution speeds. Of particular interest was the intoxicated workers' difficulty with the conceptually more complex negative syntactic reasoning problems. This difficulty was also shared by solvent workers who were not involved in that accidental intoxication. In addition, decision fatigue was observed following prolonged responding in a continuous choice reaction time task, although ability to maintain vigilance and concentration were unaffected. Taken together, these findings indicate that a single solvent intoxication can give rise to long-term cognitive sequelae in solvent workers.

Reaction time changes in workers exposed to lead.

This article provides a detailed examination of lead workers' reaction times to elucidate the underlying basis for the slowing found. Seventy workers, classified as either low, medium, or high lead exposed, completed a five-choice reaction time task using response-stimulus intervals (RSIs) between 0 and 4 s. Performance was assessed by analysing the distributional properties of correct reaction times. The effect of lead on movement time was constant across the entire movement time distribution and thus simply characteristic of slowed motor reaction time. By contrast, the effect of lead on decision time became increasingly evident at higher points in the percentile distribution, particularly at the shortest RSIs. This suggests that decision slowing is due to central, not peripheral, factors and is consistent with alternative analyses showing that the incidence of decision gaps also provide a sensitive indicator of lead effects. Subsidiary analyses showed that movement and decision slowing was correlated solely with levels of blood lead, but not with zinc protoporphyrin or urinary ALA levels.

The Automated Cognitive Test (ACT) system.

The ACT system is a key-press, menu-driven system for selecting, administering, and storing raw data from a series of specially designed psychological tasks. Associated task analysis programs process the raw data and store the resulting summary data for later statistical analysis. The system utilizes a cognitive approach to assessments of marginal toxicity by employing multiple performance parameters to specify a profile of deficits that, on the basis of a task's internal structure, can be related to functionally discrete cognitive systems. The tasks have been developed from a consideration of current cognitive theory and the areas of cognition include those of learning, memory, attention, reasoning, verbal, and spatial abilities. The ACT system is described in terms of its four major components: the cognitive tasks, the stimulus materials, the analysis methods, and the process of saving and combining summary data into files suitable for transfer to statistical analysis programs. The system thus automates the data collection to statistical analysis process.

Recovery after oral surgery with halothane, enflurane, isoflurane or propofol anaesthesia.

We have compared the recovery characteristics of four different techniques for maintenance of anaesthesia in 99 day-case patients admitted for oral surgery. All patients received propofol for induction of anaesthesia followed by halothane, enflurane, isoflurane or propofol infusion for maintenance of anaesthesia. Each patient was subjected to a battery of psychometric tests which included Spielberger state, trait, mood stress and mood arousal questionnaires, Maddox-Wing test and five-choice serial reaction time. All tests were performed before operation and at 0.5, 1, 2, 4, 24 and 48 h after operation. Performance in the reaction time test decreased significantly in the immediate postoperative period, returning almost to preoperative values by 4 h. However, only those patients who received enflurane or propofol had returned to their performance level before surgery by 4 h, although all four groups had achieved this target by 24 h. There was a further improvement in performance at 48 h. Anxiety and stress were high before surgery and decreased rapidly in the postoperative period. The Maddox-Wing test demonstrated a significant impairment in performance in the first 1 h after surgery, which returned to normal by discharge at 4 h. There were no significant differences between the four groups in these latter tests.

Short term prospective study of cognitive functioning in lead workers.

In a short term prospective study 70 male lead workers performed a series of cognitive tasks on three occasions during an eight month period. Concurrently with the cognitive testing, the concentrations of blood lead, zinc protoporphyrin (ZPP) and urinary aminolaevulinic acid (ALA) were measured. Indicators of lead absorption were stable during the study and each subject was allocated to either a low (below 20 micrograms/dl), medium (21-40 micrograms/dl), or high (41-80 micrograms/dl) group on the basis of their average blood lead concentrations. Performance deficits tended to be restricted to the high lead group and, in general, neither practice nor continued exposure during the study altered the magnitude of these deficits. The main deficit was a slowing of sensory motor reaction time, which was seen most clearly when the cognitive demands of the task were low. In the cognitively simple five choice task, blood lead concentration correlated with impaired decision making, response execution, and "lapses in concentration." In the other cognitive tasks the high blood lead group tended also to be slower by a factor of about 1.08 but the dominance of cognitive over sensory motor demands attenuated the exposure-performance correlations. The high lead group also had difficulty in recalling nouns poorly related to the focus of an earlier semantic classification task. This difficulty increased over time and was one of the few findings that correlated with all measures of lead absorption. It is concluded that the primary psychological profile of lead impairment is one of sensory motor slowing coupled with difficulties in remembering incidental information.

Cognitive functioning in lead workers.

In a cross sectional study of occupational exposure to inorganic lead 91 men performed a series of microcomputer based tasks assessing sensor motor reaction time, memory, attention, verbal reasoning, and spatial processing. Performance on the tasks was studied in relation to three ranges of blood lead concentration (low, less than 20 micrograms/dl; medium, 21-40 micrograms/dl; and high, 41-80 micrograms/dl) and exposure response correlations for blood lead concentration, zinc protoporphyrin (ZPP) (range 7-210 micrograms/dl), and urinary aminolaevulinic acid (ALA) (range 0.5-22.0 mg/l). The results show that the high group were impaired on most of the tasks used and, in general, the magnitude of the impairment correlated better with blood lead concentration than ZPP or urinary ALA. An examination of the patterns of task impairment indicated a general slowing of sensory motor reaction time which was relatively independent of the nature of the cognitive functions being tested. There was some evidence, however, suggesting mild impairment of attention, verbal memory, and linguistic processing. In general, workers with high blood lead concentrations showed clear impairment of sensory motor functions in the absence of correspondingly strong evidence for impaired processing and memory functions. It is argued that a general slowness in responding may underlie many previous reports of widespread cognitive impairment in lead workers.

Mood and cognitive functions in anaesthetists working in actively scavenged operating theatres.

Twenty-two anaesthetists participated in a study to assess the influence of occupational exposure to anaesthetic agents on mood (arousal and stress) and cognitive functions. In a cross-over design, each anaesthetist worked one day in a reference facility (for example, intensive care) and another day in a scavenged operating theatre where time-weighted exposure averaged nitrous oxide 58 p.p.m. and halothane 1.4 p.p.m. The results showed that arousal scores reached a peak in the middle of the theatre day, but this appeared to reflect the nature of operating theatre work rather than exposure. Reports of stress were also unaffected by exposure, although higher scores were associated with longer and more demanding work. Similarly, there was no evidence that exposure impaired performance of tasks assessing syntactic and semantic reasoning, verbal and spatial memory, sensory-motor reaction time and attention. Performance in these tasks was, however, sensitive to the cognitive demands of the tasks and to naturally varying non-exposure factors. It is concluded that, compared with the reference condition, the concentrations of anaesthetic agents found in actively scavenged operating theatres have no detrimental effect on either the mood or the cognitive functions of anaesthetists.

The longitudinal evaluation of verbal-reasoning in lead workers.

Four times during the course of a year, asymptomatic lead workers from the printing industry underwent a series of psychological tests assessing memory, attention, verbal-reasoning and spatial skills. In a syntactic reasoning task, the exposed group were less accurate, tended to be slower on the more complex problems and showed less consistent improvement over the year. An examination of subjects with changing blood-lead levels during the year showed that, within the exposed group, those with rising blood-lead levels were less accurate than those whose blood-leads fell or remained constant. This may indicate that effects of changing blood-lead concentrations depend upon overall level of exposure.

Memory sequelae of solvent intoxication.

A retrospective study on a small group of female workers accidentally intoxicated by organic solvents (toluene and aliphatic hydrocarbons) evaluated complaints of residual memory impairment. Memory testing was first performed two months after the intoxication with a follow-up six months later to assess recovery. The workers showed normal patterns of performance on tests of learning and short-term and longer-term memory, but marked difficulties were observed when attention had to be allocated between two resource-competing tasks. As there was no evidence of recovery by the follow-up session, the results indicate that solvent intoxication can cause neuropsychological sequelae lasting for over eight months.

Effects of 50 Hz electric currents on vigilance and concentration.

Seventy six male volunteers were studied in a crossover trial to assess the effect on the central nervous system of 50 Hz electric currents. Currents totalling 500 microamperes were passed through electrodes attached to the head, upper arms, and feet, simulating exposure to a vertical electric field of about 36 kV/m. Exposure and sham exposure sessions were assigned using double blind techniques and current passed for about 5.5 hours during the exposure session. A series of psychological tests comprising self reports of mood and performance tests of memory, attention, and verbal skills were administered. The present paper discusses the effects of those currents on vigilance and sustained concentration and examines the hypothesis that electric fields act as stressors. The results indicate that vigilance and concentration were not influenced by exposure, nor do they support the hypothesis of a stress reaction. Although brief reports of sensations at electrode sites compromised the double blind conditions to some extent, the performance changes associated with these reports were independent of exposure per se. Within the vigilance task there were two possible exposure effects on the time taken to identify non-target numbers. Firstly, the non-targets were identified more slowly during the first hour of exposure. Secondly, for subjects not reporting sensations, non-target latencies on the second day were slower in the exposed group--there were no corresponding differences on the first day. The interpretation of this effect is complicated by its apparent restriction to the second day and may indicate some kind of state dependent transfer phenomenon.

Effects of 50 Hz electric currents on mood and verbal reasoning skills.

Seventy-six male volunteers were studied in a crossover trial to assess the impact on the central system of electric currents such as might be induced by exposure to an intense power frequency electric field. Currents totalling 500 microamperes (50 Hz) were passed through electrodes attached to the head, upper arms, and feet, simulating exposure of and average man to a vertical electric field of about 36 kV/m. Exposure was continuous for a single day (5.5 hours) and the experiment was based on a double blind, counterbalanced, within subject design. A series of psychological tests examining self reports of both stress and arousal (mood checklist) and performance tests of memory, attention, and verbal skills were administered. Although the double blind conditions were compromised to some extent by reported sensations at electrode sites, the duration of these sensations was small in relation to the overall exposure or sham exposure time and did not interact with the effects apparently associated with exposure that were found. No significant difference between the exposed and sham-exposed groups was found on the first day, but on the second day the sham exposed group felt more aroused at the end of the day and their response times had improved more on the complex problems of a syntactic reasoning test. No exposure effects were apparent in self reports of stress or in performance in a semantic reasoning test, although both showed some influence of sensations. Interpretation of the exposure effects is complicated by their apparent restriction of the second test day, which may indicate some type of state dependent transfer phenomenon.