![]() ![]() The American Academy of Sleep Medicine reports that shift work disorder occurs when complaints of insomnia or excessive sleepiness occur in relation to work hours that are scheduled during the usual sleep period. Total sleep time is typically curtailed by one to four hours in night and early-morning shift workers, and sleep quality is perceived as unsatisfactory. Excessive sleepiness usually occurs during work shifts and often is accompanied by reduced alertness and impaired mental ability. The study was supported by the Congressionally Directed Medical Research Programs. ![]() Sleep duration and fatigue level from the last duty day in each work schedule were examined as a function of duty start time. The model allowed for no sleep during duty periods or during the one hour preceding and following each shift. Each hypothetical work schedule lasted six days, with constant start times and standard, nine-hour shift durations. Bowen and her research team generated 24 hypothetical work schedules with shift start times that varied by one-hour increments across the 24-hour clock. The analysis was based on the two-process model of sleep regulation, which instantiates the effects of sleep/wake homeostasis and circadian rhythms on sleep propensity and waking fatigue. The study used mathematical modeling to predict the effect of shift start time on total off-shift sleep time per 24-hour period and mean on-shift level of fatigue per duty period. “The same limitation on the number of duty hours may be either overly restrictive if during the day or too liberal if during the night.” “Shifts of equal duration differ in how fatiguing they are depending on the time of day when they are scheduled,” said Bowen. In particular, night shifts that begin after midnight may allow workers to get more sleep and experience less fatigue than shifts that start between 8 p.m. The results suggest that in addition to implementing regulations that limit the number of hours worked in a 24-hour period, employers should schedule shift start times in a way that maximizes sleep and alertness. In contrast, shifts that started just before midnight did not allow for pre-shift sleep because the timing conflicted with the body’s early evening circadian process. The researchers explained that work schedules with start times after midnight allowed workers to sleep right before the duty period, which meant that they were better-rested when the shift began. Furthermore, there was a relatively sudden decrease in predicted fatigue for duty periods starting after midnight compared with shifts that started just before midnight. The study also predicted that minimum on-the-job fatigue occurred when the shift started at 9 a.m., and maximum fatigue occurred when the work shift began at 11 p.m. and midnight yielded consistently poorer predicted performance and less than adequate predicted total sleep per 24 hours,” said lead author Angela Bowen, research assistant at the Sleep and Performance Research Center at Washington State University Spokane. “Our most interesting finding was that shifts beginning between 8 p.m. and 2 p.m., and the minimum estimated sleep duration occurred when the shift began between 8 p.m. The maximum estimated sleep duration occurred when the work shift started between 9 a.m. ![]() Results indicate that estimated sleep durations varied from 4.5 hours to eight hours according to the start time of the work shift. WESTCHESTER, IL – Regulations that limit the number of hours worked also should provide guidance for shift start times to maximize workers’ sleep opportunity and minimize the risk of on-the-job fatigue, according to a research abstract that will be presented Tuesday, June 8, 2010, in San Antonio, Texas, at SLEEP 2010, the 24th annual meeting of the Associated Professional Sleep Societies LLC. Guiding Principles for Industry Support.Young Investigators Research Forum (YIRF).Accredited Sleep Technologist Education Program (A-STEP).Advanced Practice Registered Nurses and Physician Assistants (APRN PA). ![]()
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