Effects of sleep inertia on cognitive performance following a 1-hour nap

This study investigated the effects of a 1-h nap on subsequent performance in spatial memory (SM) and logical reasoning (LR) tasks. The objective was to evaluate the duration of the effects of sleep inertia (SI). The performance was measured in two independent groups of subjects. The 1-h nap took place at 00:00 h in group 1 and at 03:00 h in group 2. In each task, the experimental design comprised one no-nap condition in which subjects had no sleep before the night tests, and a nap condition that comprised the 1-h nap followed by the test sessions. To measure the duration of SI effects, the subjects were tested in two 30-min sessions and the data in each session were analysed in sub-units of time of 3 min each. In each task the results showed no effects on accuracy, and no circadian effects of napping were found. In each task, analyses of pooled data of the two groups showed that the performance in the 1-h nap condition exhibited significant reductions of speed immediately following awakening, when compared with no-nap, reflecting SI effects. In SM, the slowing lasted 24 min, and 27 min in LR. Practical implications of the results are discussed.     

Auditory evoked potentials as a function of sleep deprivation

Event-related brain potentials (ERPs) were studied in subjects deprived of sleep over a 48-h test period to assess the effects of different durations of continuous wakefulness on ERP components and to determine whether changes in the ERP components were related to changes in performance. Forty subjects were randomly assigned to either an experimental (sleep deprived) group (n = 30) or a control (not sleep deprived) group (n = 10). For the experimental subjects, ERP and performance measures were obtained in four-h test blocks throughout the 48-h period. Performance was assessed using the Walter Reed performance assessment battery. The control subjects were tested at the same times except during designated sleep periods. Both performance and evoked potential measures showed systematic changes over the experimental test period in association with sleep deprivation, time of day, and repeated testing. The latency of the N2 component of the evoked potential covaried with throughput measures on the performance assessment battery across the 12 four-h test blocks of the experiment. These data suggest that ERPs reflect central processes that change across the sleep deprivation period and that ERP measures might be useful in assessment and prediction of performance degradation under adverse conditions such as sleep loss.     

Effects of age and domestic commitment on the sleep and alertness of female shiftworkers

Abstract

In this study, the combined effects of age and domestic commitment on sleep duration, sleep difficulties and alertness in a sample of female shiftworkers were studied. A total of 572 nurses working in general hospitals in England completed a questionnaire. Two main shift systems were worked by the nurses: permanent nights or rotating shifts. Initial analysis revealed significant differences between these two groups of nurses, resulting in separate analysis of each group. Regression analysis showed that although older nurses had shorter sleep duration they did not report more sleep difficulties, in addition, their overall on-shift alertness was higher compared to younger nurses. Domestic commitment, defined as the number of dependants in the household and the level of perceived work-home conflict, not only reduced sleep duration, but also resulted in more sleep difficulties and lower on-shift alertness for most of the shifts. Two implications with regards to the relationship between age and sleep are discussed. First, the study points to the relevance of considering both biological and social factors when looking at age and sleep. Secondly, the study shows that the effects of age on sleep duration and sleep difficulties are not similar. This finding requires further research, especially in the light of the higher levels of alertness reported by older nurses.     

Monitoring the improvement of an overall industrial performance based on a Choquet integral aggregation

The design and use of performance measurement systems (PMSs) have received considerable attention in recent years. Indeed, industrial performances are now defined in terms of numerous criteria to be synthesized for overall improvement purposes. The analysis of the literature leads to the conclusion that most of the proposed approaches deal with a qualitative approach of this multi-criteria issue. But only a few quantitative models for PMSs have been proposed in order to better monitor the continuous improvement cycle. Among them, the one proposed by the authors, based on a Choquet integral aggregation operator, allows to express an overall performance according to subordination and transverse interactions between the criteria involved. But, as this model is nonlinear, it is useful to define pieces of information aimed at aiding the manager to improve the performance situation. Thus, this article is a contribution to the managers’ requirements for optimizing the improvement of the overall performance versus the allocated resources. In this view, indexes of efficiency and predictive improvement are proposed. The approach is applied to a case study submitted by a company manufacturing kitchen and bathroom furniture which wants to upgrade the monitoring of its “environment and quality improvement plan”.