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Biomedical subjects

Simon Folkard

Publications and source records attributed to Simon Folkard.

13 recordsLinked to original sources
PubMed2006

Modeling the impact of the components of long work hours on injuries and "accidents".

BACKGROUND: Many of the industrial disasters of the last few decades, including Three Mile island, Chernobyl, Bhopal, Exxon Valdez, and the Estonia ferry, have occurred in the early hours of the morning. Follow-up investigations concluded that they were at least partially attributable to human fatigue and/or error. The potential impact of long work hours on health and safety is a major concern that has resulted in various work hour regulations. METHODS: The risk of injuries and "accidents" (incidents) associated with features of work schedules from published epidemiological studies are pooled using an additive model to form a "Risk Index." The estimated risks of an incident for various standard work schedules are presented using the proposed model. RESULTS: The estimated risk of an injury or accident associated with any given number of weekly work hours varies substantially depending on how work hours are comprised. The risk depends on the length and type of shift, as well as the frequency of rest breaks. CONCLUSIONS: We conclude that placing a limit on the risk associated with a particular work schedule is likely more effective than setting daily, weekly or monthly work hour regulations in keeping workplace safety within acceptable limits.

Accidents, Occupational↗
PubMed2006

Searching for signs, symbols, and icons: effects of time of day, visual complexity, and grouping.

Searching for icons, symbols, or signs is an integral part of tasks involving computer or radar displays, head-up displays in aircraft, or attending to road traffic signs. Icons therefore need to be designed to optimize search times, taking into account the factors likely to slow down visual search. Three factors likely to adversely affect visual search were examined: the time of day at which search was carried out, the visual complexity of the icons, and the extent to which information features in the icon were grouped together. The speed with which participants searched icon arrays for a target was slower early in the afternoon, when icons were visually complex and when information features in icons were not grouped together to form a single object. Theories of attention that account for both feature-based and object-based search best explain these findings and are used to form the basis for ways of improving icon design.

Adolescent↗
PubMed2006

The impact of rest breaks on temporal trends in injury risk.

This study examined the impact of rest breaks on temporal trends in industrial accident risks in an attempt to replicate earlier findings of a linear increase in risk as a function of elapsed time on task. In two separate studies, the trend in work-related injuries were studied in relation to the timing of rest breaks. In study one, comparisons were made between on- and off-track workers on weekly rotating three-shift systems operating in a large engineering company. Records of on-duty injuries that occurred over 12 months were examined (N = 4645 incidents). Study two involved interviewing patients who had suffered work-related hand injuries in a variety of occupational settings (N = 407 patients). Hierarchical log linear analysis was used in both studies. In study one, risk increased from the first to the second half-hour of continuous work following a break, but then remained relatively constant in subsequent half-hour periods, although there was a fall in the third half-hour for on-track workers. In some of the data, there was also a decrease in risk in the period leading up to the end of a work period. There was a sharp decline in reported injuries toward the very end of a shift, but otherwise the observed trends did not differ between successive periods of continuous work or between morning, afternoon, and night shifts. In study two, risk increased from the first to the second half-hour of continuous work and then remained relatively constant in the third half-hour. The contrast between the current and previous findings may be due to the relatively unique work environment of the previous study. It is suggested that the current trends reflect the effects of working in a relatively unconstrained task environment, and that causes other than fatigue may underlie the trends observed in both the previous and current studies.

Accident Prevention↗
PubMed2006

Estimating the circadian rhythm in the risk of occupational injuries and accidents.

The authors recently published a prototypic Risk Index (RI) to estimate the risk of critical errors associated with shift systems. This RI was based on published trends in the relative risk of injuries and accidents, and a simple additive model was proposed to estimate the risk for a given shift system. However, extending the RI to irregular work schedules requires an estimation of the phase and amplitude of the circadian rhythm in risk. This paper integrates the published evidence on three independent sources of data that allow such estimations to be made: the trend in risk over a 24 h day, over the course of the night shift, and across the three different (8 h) shifts. Despite potential confounders, maximum risk (i.e., acrophase = peak time) estimates across these three trends showed a remarkable consistency, with all three estimates occurring at about midnight, although the amplitude estimates varied considerably. The best estimate of the amplitude of the circadian rhythm in risk would appear to be that based on trend over the three (8 h) shifts, as this trend is the least confounded. The estimated acrophase (peak time) in risk appeared earlier than would be predicted from consideration of the circadian rhythm in alertness, fatigue, or performance on simple interpolated tasks, such as reaction time or performance on the Psychomotor Vigilance Test.

Accident Prevention↗
PubMed2005

Shiftwork: safety, sleepiness and sleep.

This brief paper reviews the available published literature on shiftwork and safety that allows the relative risk of "accidents" or injuries associated with specific features of shift systems to be estimated. Three main trends in risk are discussed, namely that (i) risk is higher on the night shift, and to a lesser extent the afternoon shift, than on the morning shift, (ii) risk increases over a span of shifts, especially so if they are night shifts, and (iii) risk increases with increasing shift length over eight hours. We discuss that some of these trends are not entirely consistent with predictions derived from considerations of the circadian variations in sleep propensity or rated sleepiness, and consider factors relating to sleep that may underlie the observed trends in risk. Finally, the practical implications of the trends in risk for the design of safer shift systems are discussed.

Accidents, Occupational↗
PubMed2004

Flexible working hours, health, and well-being in Europe: some considerations from a SALTSA project.

The project brought together researchers from 9 EU-Countries and resulted in a number of actions, in particular the following: (a) There is an urgent need of defining the concept of flexible working hours, since it has been used in many different and even counterintuitive ways; the most obvious distinction is where the influence over the working hours lies, that is between the "company-based flexibility" and the "individual-oriented flexibility"; (b) The review of the Legislation in force in the 15 European countries shows that the regulation of working times is quite extensive and covers (Council Directive 93/104/EC) almost all the various arrangements of working hours (i.e., part-time, overtime, shift, and night work), but fails to provide for flexibility; (c) According to the data of the Third EU Survey on Working Conditions, longer and "irregular" working hours are in general linked to lower levels of health and well-being; moreover, low (individual) flexibility and high variability of working hours (i.e., company-based flexibility) were consistently associated with poor health and well-being, while low variability combined with high autonomy showed positive effects; (d) Six substudies from different countries demonstrated that flexible working hours vary according to country, economic sector, social status, and gender; overtime is the most frequent form of company-based flexibility but has negative effects on stress, sleep, and social and mental health; individual flexibility alleviates the negative effects of the company-based flexibility on subjective health, safety, and social well-being; (e) The literature review was able to list more than 1,000 references, but it was striking that most of these documents were mainly argumentative with very little empirical data. Thus, one may conclude that there is a large-scale intervention ongoing in our society with almost completely unknown and uncontrolled effects. Consequently, there is a strong need for systematic research and well-controlled actions in order to examine in detail what flexible working hours are considered, what and where are their positive effects, in particular, as concerns autonomy, and what regulation seem most reasonable.

Adolescent↗
PubMed2004

Toward a "Risk Index" to assess work schedules.

This article describes our preliminary attempt to develop a Risk Index to estimate the risk of human error on different work schedules based on trends in the relative risk of accidents and injuries, rather than on hypothetical intervening variables such as alertness, fatigue, or performance on interpolated tasks. We briefly review trends in risk from the published epidemiological studies that have ensured that the a priori risk was constant. A simple Risk Index based on an additive model is developed on the basis of these trends, and we illustrate how it may be used to assess work schedules. Finally, we compare the results from this Risk Index with those from the UK HSE's Fatigue Index and point out the discrepancies that emerge. We conclude that our risk-based modeling approach may assist in developing safer work schedules and also increase our understanding of this complex, multifaceted area.

Accidents, Occupational↗
PubMed2004

Analyzing irregular working hours: lessons learned in the development of RAS 1.0--The Representation and Analysis Software.

Actual working hours of employees vary widely, especially in the transportation industry. We developed a tool, the RAS (Representation and Analysis Software), to ease the assessment of such irregular hours and the transfer of existing knowledge of proper schedule design to the problem of irregular hours. This article discusses several critical design questions that were addressed during software development in order for it to assess irregular work patterns, including the (1) importance, in spite of a lack of established definitions, of basic concepts like, e.g., night shift, (2) difficulty of modeling and adapting existing knowledge on proper design, and (3) large number of analytical methods and additional data beyond company schedule that are necessary to meet the needs of various research groups. This article describes how the RAS addresses these three issues by illustrating its application to the work schedule of a train driver involved in the Hinton train disaster.

Employment↗
PubMed2004

Predictions from the three-process model of alertness.

This paper summarizes a computer model for predicting alertness/performance in daily life. The model uses the timing of work hours (and/or sleep hours) as input and uses both a circadian and a homeostatic component (amount of prior wake and amount of prior sleep) that are summed to yield predicted subjective alertness (on a scale between 1 and 21). The model also includes prediction of psychomotor performance on various tasks, an identification of levels at which the risk of performance/alertness impairment start, as well as a prediction of sleep latency and time of awakening from sleep. The model is currently being used to evaluate work/rest schedules for navy, airline and railway applications. It is also used for teaching sleep/wake regulation and for generating research hypotheses.

Circadian Rhythm↗
PubMed2004

Trends in the risk of accidents and injuries and their implications for models of fatigue and performance.

Models based on measures of fatigue and performance make the implicit assumption that they will be successful in predicting risk. The present paper reviews the available literature on shiftwork safety in which real measures of accidents or injuries could be pinpointed in time and in which the a priori risk appeared to be constant. Three main problems for the models emerged from this review: 1) risk was significantly higher on the afternoon shift than on the morning shift; 2) the dominant peak in risk over the course of the night shift occurred at about midnight; and 3) risk increased substantially over spans of four successive nights. It is suggested that the relationship between risk and fatigue may be non-linear, that models may have overestimated the recovery during short sleeps, and that day sleeps between night shifts may be less recuperative than normally timed night sleeps of the same length.

Accidents↗
PubMed2003

Shift work, safety and productivity.

The arguments in favour of introducing shift work clearly depend on productivity and safety being maintained at an acceptable level. However, the evidence reviewed in this paper clearly indicates that both productivity and safety may be compromised at night. More specifically, safety declines over successive night shifts, with increasing hours on duty and between successive rest breaks. The only known way to minimize these problems is to improve shift systems with respect to these factors. However, these factors need to be considered in combination with one another since, for example, a long night shift that includes frequent rest breaks might well prove safer than a shorter night shift with less frequent breaks.

Accidents, Occupational↗
PubMed2003

Perception and predictability of travel fatigue after long-haul flights: a retrospective study.

BACKGROUND: The impact of travel fatigue and jet lag varies between individuals and may significantly affect the ability of some to perform their occupational role following a transmeridian flight. It would be advantageous in an occupational setting to be able to predict prior to travel those who may suffer most. METHODS: A Traveler Profile Questionnaire was developed to assess the perceived severity of travel fatigue in 100 subjects making transmeridian flights. RESULTS: The questionnaire provided an internally consistent measure of fatigue and confirmed that subjects experienced greater symptoms of travel fatigue following east/west flights when compared with north/south. Easterly travel was rated marginally worse than travel in a westerly direction. The respondents scores as measured by the Circadian Type Inventory (Folkard 1987) and Composite Morningness Questionnaire (Smith 1989) were used to identify whether such tools could be used as indicators of susceptibility to the effects of travel fatigue. After allowing for a gender difference, increased rigidity in sleeping habits as shown by a decrease in the Flexibility/Rigidity score on the Circadian Type Inventory was associated with an increase in the composite 'severity' score for travel fatigue derived from ratings of specific physiological symptoms. CONCLUSIONS: The Traveler Profile Questionnaire, while internally consistent was nonetheless insufficient to be used in a predictive capacity to identify those individuals who would suffer most from the effects of travel fatigue.

Adult↗