By interactionofbath, 29-Oct-2012 10:17:00
A University of Surrey study concluded that the lack of sleep experienced by night shift workers interferes with the productivity and can cause health problems including:
- Metabolic syndrome (decreased HDL cholesterol, elevated triglycerides)
- Glucose intolerance/diabetes
- Heart disease and cancer.
Night shift workers also have more accidents and errors are also more likely. For example, the incidence of seriously improper medical decisions was 36% higher for Interns working extended shifts rather than a traditional shift.
Performing work tasks when the body is producing hormones that encourage sleep (circadian rhythm desynchrony) is thought to be the underlying reason. Most long-time or permanent night-shift workers do not show adaptation of their circadian rhythm to their work day, and less than a quarter show even partial adaptation. With a marked reduction of daytime sleep hours, night workers appear to be sleep deprived.
Night shift workers are able to alter their circadian cycle in select work environments when there are no social or family commitments and when there is no natural morning light at the end of their night shift.
For ergonomists, the study highlights the health and productivity issues related to working nights or extended shifts. While changing work methods can reduce the need to work nights, a night shifts are unavoidable in some industries. According to the author, encouraging an adaptive shift of the worker’s circadian rhythms to coincide with night hours may be favourable, except where there commitmet to night shifts is only brief, when no interference with the normal body rhythms is encouraged outside the use of stimulants such as caffeine.
Melatonin, a hormone secreted by the pineal gland, is primarily produced during the night-time body state. The concentration of melatonin, which can be measured in the plasma, saliva, or as a urinary metabolite), provides a good indication of the circadian clock time. Modifying the levels of melatonin through the use of light treatment during the 'biological' night could help regulate the sleep/activity cycle. Exercise, social cues, timing of food ingestion and food content also seem to influence the circadian clock to varying degrees. A worker's toal sleep hours could also be increased by taking a low dose of melatonin and lying down in a dark room in the early evening prior to a night work shift.
Switching from a day shift to a night shift (with a likely 20-24 hours of no sleep), may lead to a performance decrements similar to those associated with having an illegally high blood alcohol level.
By interactionofbath, 17-Sep-2012 15:03:00
InterAction of Bath will be at the annual BIME (Bath Institute of Medical Engineering) public lecture at the University of Bath on Wednesday 3rd October at 7 pm. Professor Gail Mountain will describe how technology can be used to meet the needs of an ageing population. Read more ...
By interactionofbath, 12-Sep-2012 10:43:00
It was another carnival-like atmosphere outside our offices as local members of Britain's Olympic and Paralympic teams paraded through the city on an open-topped bus. InterAction of Bath joins the general celebration for the achievements of Team GB.
By interactionofbath, 31-Jul-2012 10:08:00
According to a report released on Monday by an independent panel commissioned by the Japanese government, the catastrophic Fukushima reactor meltdowns had less to do with the earthquake and tsunami that hit Japan in March last year and more to do with the failure of the plants owners and the government to anticipate and prepare for emergencies on such an epic scale.
The report accuses the Nuclear and Industrial Safety Agency of failing to tell the media that the plant's fuel rods had possibly melted, even though it knew this was likely. To counter the risk of further radiation leakage, the removal of the rods from a storage pool at the facility started last week in the first stage of a programme to remove unused and used fuel from the reactor, a process that could take years.
By interactionofbath, 20-Jun-2012 11:12:00
Last week we enjoyed delivering another two-day training course at Aspire Consulting in Tamworth. We had a really good time and, from the feedback we received, the good folk at Thales did too.
Our next course is planned for Bath on the 10th and 11th of September. If you would like to book a place, please call or email us.
By interactionofbath, 22-May-2012 15:25:00
The Olympic torch visits InterAction of Bath! See the pictures taken from a window in our office.
By interactionofbath, 24-Apr-2012 10:46:00
Occupational fatigue is relatively common within the general population and has been linked to reduced performance, injury and longer term ill-health. Psychological fatigue is defined as a subjectively experienced disinclination to continue performing the task at hand. It generally impairs human efficiency when individuals continue working after they have become aware of their fatigue. It does not depend on energy expenditure and cannot be measured simply in terms of performance impairment. The interacting causal contributions to fatigue are the length of continuous work spells and daily duty periods, time available for rest and continuous sleep, and the arrangement of duty, rest, and sleep periods within each 24-h cycle.
Several studies have looked at performance decrements in driving.
Brown (1984) showed that fatigue was insufficiently recognized and reported as a cause of road accidents and that its effects stem largely from prolonged and irregular working hours, rather than simply from time spent at the wheel.
Philip et al (2005) found that restricted sleep can induce important performance degradation even during relatively short driving times (105 min). There are also major inter-individual differences in performance under sleep restriction.
In a study of maritime populations, Wadsworth et al (2008) found a strong link between fatigue and poorer cognitive and health outcomes, with fatigue the most important of a number of risk factors.
In another study, young male Naval volunteers were denied normal nocturnal sleep and maintained on a 60-min lreatment-160-min testing schedule during 40 consecutive hrs. Ten subjects bicycled, 20 subjects controlled EEG activity during bedrest, and 10 subjects napped. Eight measures of addition, auditory vigilance, mood, and oral temperature were obtained. The Bedrest group showed significant impairment on all eight measures, and thus, gave no support to lite forced-rest theory of sleep function. The Exercise group was worse than the Nap and Bedrest groups for all measures. In spite of fragmented, reduced sleep (about 3.7 hrs per 24 hrs), the Nap group had no impairment on six of the measures. The results suggest that exercise increases the impairment due to sleep loss, and naps reduce or remove this impairment. Bedrest is not a substitute for sleep.
In medicine, where sleep deprivation has sometimes been seen as a badge of honour, there is a realisation that even modest amounts of sleep loss over short periods (about two hours a night over one week) can accumulate and manifest themselves as an irresistible tendency to fall asleep during inappropriate or dangerous situations. Of course, completion of medical training does not render doctors immune to problems related to sleep deprivation. Prolonged work periods without sleep can increase the risk of complications for patients and may be detrimental to physicians’ health. A 10-year study noted that the rates of surgical complications were substantially elevated among patients whose surgeon had had less than six hours of uninterrupted sleep the night before. A 2010 study noted that at least two nights’ adequate sleep are needed following a working night on call for doctors to feel fully refreshed.
Kahol et al (2008) found that fatigue and sleep deprivation caused a significant deterioration in the surgical residents’ cognitive skills as measured by virtual reality simulation. Psychomotor skills were also negatively impacted during tasks that required a combination of psychomotor and cognitive skills.
Some studies have compared the performance effects of sleep deprivation to those associated with alcohol consumption. Williamson and Feyer (2000) found that after 17–19 hours without sleep, performance was equivalent or worse than that at a blood alcohol concentration of 0.05%. Response speeds were up to 50% slower for some tests and accuracy measures were significantly poorer than at this level of alcohol. After longer periods without sleep, performance reached levels equivalent to the maximum alcohol dose given to subjects (BAC of 0.1%).
In a study of nightshift workers, Dawson 1998 found that moderate levels of sustained wakefulness produced decrements in cognitive psychomotor performance comparable to those at moderate levels of alcohol intoxication in social drinkers. He also found that the relationship between sustained wakefulness and cognitive performance is complex, with three distinct phases. In the first phase (0-10 hours) performance remained relatively stable; in the second phase (10-26 hours) performance declined linearly at 0.74% per hour, and in the third phase (26-28 hours), performance improved again presumably reflecting the well reported circadian variation in cognitive psychomotor performance. Sustained wakefulness seems to affect complex cognitive psychomotor abilities before simpler abilities – e.g. 24 hours of sleep deprivation may be necessary to show performance decrements in simple perception and response tasks while in more complex tasks requiring attention resource functions, decrements may be observable sooner.
By interactionofbath, 12-Mar-2012 12:40:00
InterAction of Bath is now on Twitter. We already have a handful of followers. Join them to follow us.
By interactionofbath, 24-Feb-2012 12:52:00
Ergonomists must often make recommendations for acceptable physcial demands for a wide variety of tasks. Although there is a large database in the literature for single-effort strength, most occupational tasks require repetitive efforts. In such cases the recommended demands should be lower than the maximum strength. But by how much? As yet, there is not a database of data available to guide the prediction of acceptable submaximal, repeated efforts.
In an article from Human Factors, December 2011, Jim Potvin of McMaster University, Canada describes an equation for "Predicting Maximum Acceptable Efforts [MAE] for Repetitive Tasks" based on Duty Cycle [DC], where DC represents the total effort duration divided by the cycle time.
According to Jim Potvin, this equation, which takes DC to the exponent 0.24, predicted MAE very well
MAE = (1 – DC ^0.24) x maximum voluntary effort
On an assembly line where women are required to make ten power grip efforts during a 65s cycle, with each grip of 0.55s duration:
DC = (10 efforts/cycle x 0.55s/effort) / 65s = 0.085 (8.5% of each cycle)
MAE = (1 - 0.553427) x MVE = 44% of maximum grip strength
This equation allows practitioners to make corrections of the large strength database to estimate acceptable force and torque limits for repetitive occasional tasks.
As ever, there are a few caveats: the equation applies only when the demands of work do not vary substantially over 8-hour day and when the work is not complex, with multiple task elements; at this stage, too, the equation should only be used to determine female MAE values.
We accept that the equation is not perfect and that it doesn't provide all the answers, but we also believe that, as part of the ergonomist's toolkit, it could help many practitioners in a range of settings.
You are viewing the text version of this site.
Need help? check the requirements page.