Investigation of task performance variations according to task requirements and alertness across the 24-h day in shift-workers

International audienceThe study investigated time-of-day effects on task performance in shift workers in different tasks (reaction time, discrimination, probe recognition, free recall), by varying task-specific features. On each of six recordings, each programmed on a different day and in a randomised order, operators rated alertness and performed different tasks. Self-rated alertness varied according to a typical diurnal trend. Time of day also affected reaction time (slower responses at 03:00 hours), discrimination performance (lower accuracy at 03:00 hours in the most difficult condition) and recall (superior recall at 07:00 and 11:00 hours following deeper processing at encoding). The data demonstrated time-of-day effects on cognitive processes also involved in many real-job activities, despite the lack of control for a number of exogenous factors known to interfere with performance in work settings. Since in the cognitively more loaded tasks, time-of-day effects depended on task conditions, the findings are of operational concern in shift-work situations involving differential task requirements. In a real-job setting, performance variations were observed according to time of day and task requirements in a set of cognitively more or less demanding tasks. Task-specific research across the 24-h day enables a better understanding of operators' tasks and the development of supporting technology

Investigation of Air Traffic Controllers' Response Strategies in a Free Recall Task: What Makes Auditory Recall Superior to Visual Recall?

International audienceThis study investigated the response strategies displayed by air traffic controllers (ATCs) recalling visually and auditory presented verbal material in a free recall task. The end-of-list advantage for auditory compared to visually presented item lists (modality effect) was explored by using the procedure described by Beaman and Morton (2000). Results revealed that ATCs’ response sequences frequently included ordered end subsequences of 2 to 6 items. These end subsequences were recalled as an initial run at a similar rate in both modalities, although they occurred more frequently in positionsother than initial recall positions in the auditory modality. These results replicate and extend those reported in controlled laboratory studies, and this is despite ATCs’ extended experience with processing visual information. The results are discussed in terms of the functional limitations of visual and auditory item processing and their relevance to air traffic control activities, training, and selection

DIFFERENTIAL 24-HOUR VARIATION OF ALERTNESS AND SUBJECTIVE TENSION IN PROCESS CONTROLLERS: INVESTIGATION OF THE RELATIONSHIP WITH BODY TEMPERATURE AND HEART RATE

International audienceThe effects of shift and time-on-shift on alertness and perceived tension, as well as related physiological variables, were investigated in satellite controllers working a rapid forward rotating three-shift system. In controlled laboratory conditions, subjective tension and HR have been reported to display circadian variation and marked sensitivity to external factors. We examined whether circadian variations were masked for these particular variables in real-job conditions, unlike for alertness and body temperature , which have been repeatedly shown to display circadian variation in these conditions. This hypothesis was tested in a repeated-measures design by collecting alertness and tension self-reports and recording operators' sublingual temperature on three occasions on each shift and HR continuously throughout shifts. Alertness and body temperature varied according to a typical diurnal trend; subjective tension was only enhanced on the initial recording of each shift (compared to the remaining ones), while HR displayed an intermediary trend. Intra-subject correlations revealed a positive relationship between alertness, oral temperature, and HR, while no such relationship was found for subjective tension. These results support the hypothesis of a close dependence of alertness and temperature, and to a lesser extent for HR, on endogenous mechanisms in this job-situation. In addition, some situation-specific factors, such as job-demand, would affect subjective tension and partially mask the circadian variations in HR. (Author correspondence: [email protected]

Mnemonic Processing in Air Traffic Controllers: Effects of Task Parameters and Work Organization.

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What is the relationship between mental workload factors and cognitive load types?

International audienceThe present study tested the hypothesis of an additive interaction between intrinsic, extraneous and germane cognitive load, by manipulating factors of mental workload assumed to have a specific effect on either type of cognitive load. The study of cognitive load factors and their interaction is essential if we are to improve workers' wellbeing and safety at work. High cognitive load requires the individual to allocate extra resources to entering information. It is thought that this demand for extra resources may reduce processing efficiency and performance. The present study tested the effects of three factors thought to act on either cognitive load type, i.e. task difficulty, time pressure and alertness in a working memory task. Results revealed additive effects of task difficulty and time pressure, and a modulation by alertness on behavioral, subjective and psychophysiological workload measures. Mental overload can be the result of a combination of task-related components, but its occurrence may also depend on subject-related characteristics, including alertness. Solutions designed to reduce incidents and accidents at work should consider work organization in addition to task constraints in so far that both these factors may interfere with mental workload

Vitamin D deficiency is an independent risk factor for PTDM after kidney transplantation

International audienceAn association between 25 hydroxyvitamin D [25(OH)D] deficiency and type 2 diabetes was observed in the general population. Such association was not investigated in kidney transplant recipients. We prospectively evaluated 444 patients following primary kidney transplantation between 2000 and 2010. The 25(OH)D level at transplantation was classified into three grades: deficiency (< 10 ng/ml), insufficiency (≥ 10 and < 30 ng/ml), and normal range (≥ 30 ng/ml). Time to Post-Transplant Diabetes Mellitus (PTDM) was defined according to the day of first prescription of hypoglycemic treatment. The 25(OH)D level at transplanta-tion was deficient in 88 patients, insufficient in 264 patients, and normal in 92 patients. At 1 year post-transplantation, cumulative incidence of PTDM was 13.2%. Cox multivariate analysis indicated that 25(OH)D deficiency (≤ 10 ng/ml) at the time of transplantation was an independent risk factor for PTDM within the first year post-transplantation (HR = 2.41, 95% CI 1.01-5.75, P = 0.048), whereas insufficiency tended to increase this risk, although not significantly. 25 (OH)D deficiency is a new independent risk factor for PTDM within the first year after kidney transplantation. Our study suggests that 25(OH)D may be a marker of general health in kidney transplant recipients and could alert clinicians for PTDM risk

Ability of family members to predict patient's consent to critical care research.

International audienceOBJECTIVE: A European Union Directive provides for the designation of a surrogate who can consent to or refuse inclusion of an incapacitated patient in research studies. The accuracy with which surrogates consent to research on behalf of patients has not been evaluated in the intensive care unit (ICU). METHODS: A prospective multicenter study was conducted in ten ICUs of the French Famirea study group between July and October 2004. Two hypothetical studies were simultaneously submitted to the patient, surrogate, and physician at the time that the patient was discharged to a ward. One study involved minimal risk and the other greater-than-minimal risk to the patients. RESULTS: With the minimal risk study there was patient-surrogate discrepancy in 32% of cases and patient-physician discrepancy in 25%. Corresponding figures with the greater-than-minimal risk study were 42% and 46%. None of the collected variables differed significantly between cases with and without patient-surrogate discrepancy. CONCLUSIONS: Family members designated to serve as surrogate decision makers may fail to accurately consent to research for critically ill patients in one-third to nearly one-half of cases