Coal Age

MAY 2018

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May 2018 39 circadian rhythms continued Measuring Fatigue People experience fatigue to varying de- grees, and fatigue-causing factors affect some more than others. A person's age or general health might affect their sensitiv- ity to fatigue. However, there are ways to measure fatigue, which can be a positive first step in addressing it. Subjective Methods–Subjective meth- ods for measuring an individual's fatigue include surveys and self-questionnaires, such as the Fatigue Severity Scale (FSS). Although this scale does not exactly mea- sure "severity," it does help to evaluate the impact that fatigue has on a person's daily life. In the same way, the Psychomotor Vig- ilance Test (PVT) determines the impact of fatigue by measuring reaction time and alertness, and the Karolinska Sleepiness Scale (KSS) assesses subjectively how sleepy a person feels. Thus, these methods give a way to understand the problem on an individual level. Objective Methods–More direct meth- ods, such as measuring a person's core body temperature or taking blood sam- ples to measure hormone levels, can de- termine if there is a disruption of circadian rhythms. However, these procedures are highly invasive and cannot easily be done in real time, making them impractical for measuring fatigue in a working mine. Sa- liva tests to measure the hormone mela- tonin, a common indicator for circadian rhythms, are somewhat more practical. Other methods seek to identify fatigue as it happens. These include facial recognition and eye-tracking technology, which mon- itor a worker's apparent fatigue level. This approach can make workers uncomfort- able, as they might consider it an invasion of privacy or disruptive to their work. Dealing With Fatigue A more active way of addressing worker fatigue is to use a preventative method. To control worker schedules and help limit shift work and excessive overtime, mine operators can implement a fatigue man- agement system. These types of systems may help to manage fatigue resulting from shift work by first detecting and tracking it, and then making changes to either avoid or manage fatigue over time. Yet for underground miners, even with a fatigue management system in place there is still the problem with lack of suffi- cient light. In this case, a lighting interven- tion may help to prevent the disruption of circadian rhythms. Other workers facing a similar issue are those working in Antarcti- ca, who spend the sunless winter months in dark, isolated areas where the only light is from artificial sources. Similarly, the crew aboard U.S. Navy submarines may spend months at sea without natural light while utilizing strict shift work schedules. Both were able to successfully adopt a lighting solution using highly blue-enriched light sources to provide enough illumination and short-wavelength light throughout the day to reduce the misalignment of cir- cadian rhythms (Najjar et al., 2014; Young et al., 2015), which also led to an increase in alertness and quality of sleep. Using these lights during the night shift, however, would contribute to the disruption of circadian rhythms. Yet work- ers still need light to do their jobs. One potential solution is to use light sources with longer wavelengths of light falling in the red spectrum. Research has shown that red light can increase alertness and performance without impacting circadian rhythms (Figueiro et al., 2016). Such a lighting solution would be chal- lenging to implement in a mine environ- ment, and the exact nature of an interven- tion remains a subject for future research. However, improving the lighting conditions has the benefit of making hazards more vis- ible to miners, and NIOSH researchers are hopeful it can also serve as an effective fa- tigue intervention in underground mines. Max J. Martell is a mining engineer work- ing at the National Institute for Occupa- tional Safety and Health's Pittsburgh Min- ing Research Division. He can be reached at Disclaimer The findings and conclusions in this paper are those of the authors and do not neces- sarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. References • Boyce P. (2014). "Human factors and lighting." CRC Press. • Dawson D., Fletcher A., and Hussey F. (2000). "Beyond the midnight oil: Parliamentary inquiry into managing fatigue in transport." Adelaide Cen- tre for Sleep Research. University of South Australia. • Figueiro M., Sahin L., Wood B., and Plitnick B. (2016). "Light at night and measures of alertness and perform- ance: Implications for shift workers." Biological Research for Nursing. 18(1) 90-100. • Kecklund G., and Axelsson J. (2016). "Health consequences of shift work and insufficient sleep." The BMJ. 355:i5210. • Najjar R., Wolf L., Taillard J., Sch- langen L., Salam A., Cajochen C., Gronfier C. (2014). "Chronic artifi- cial blue-enriched white light is an effective countermeasure to delayed circadian phase and neurobehav- ioral decrements." PLoS ONE. 9(7): e102827. • Schmidt D. (2015). "Technologies col- lide for surface safety." Coal Age. • Young C., Jones G., Figueiro M., Soutière S., Keller M., Richardson A., Lehmann B., Rea M. (2015). "At- sea trial of 24-h based submarine watchstanding schedules with high and low correlated color temperature light sources." Journals of Biological Rhythms. 30(2) 144–154. • Watson N., Badr M., Belenky G., Bli- wise D., Buxton O., Buysse D., Ding- es D., Gangwisch J., Grandner M., Kushida C., Malhortra R., Martin J., Patel S., Quan S., and Tasali E. (2015). "Joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Soci- ety on the recommended amount of sleep for a healthy adult: method- ology and discussion." Sleep. 38(8): 1161–1183.

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