UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADPO10472 TITLE: Assessing the Adaptability to Irregular Rest-Work Rhythms in Military Personnel DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report: TITLE: Individual Differences in the Adaptability to Irregular Rest-Work Rhythms/Status of the Use of Drugs in Sleep-Wakefulness Management [les Differences entre individus concernant les facultes d' adaptation aux rythmes irreguliers activite-repos/le point sur l'utilisation des medicaments pour la gestion des periodes veille-sommeil] To order the complete compilation report, use: ADA388183 The component part is provided here to allow users access to individually authored sections f proceedings, annals, symposia, ect. However, the component should be considered within he context of the overall compilation report and not as a stand-alone technical report. hfollowing cmponent part numbders 0npri4 ADP010453 thru. ADP010473 UNCLASSIFIED e the compilation report-
ASSESSING THE ADAPTABILITY TO IRREGULAR REST-WORK RHYTHMS IN MILITARY PERSONNEL Silvio Porclh 1 ' Maria Casagrande 1 ',2, Michele Ferraral,2 1 Aeronautica Militare Italiana, CSV Reparto Medicina Aerospaziale Pratica di Mare, 00040 Pomezia (Roma) Italy 2 Dipartimento di Psicologia - Universitd di Roma "La Sapienza" Via del policlinico 155 00161 Roma Operational decreases in performance work hours, it is possible to adopt several resulting from sleep deprivation or irregular non-pharmacological alertness management sleep-wake patterns are well knovni and are strategies aimed to: becoming increasingly important in today's a) optimize activity-rest schedules; industrialized society. Excessive sleepiness b) maintain adequate levels of vigilance and at unusual hours is estimated to affect perfornaance; approximately 5% of the general population and is associated with increased morbidity. c) select people with the most useful psychological, psychophysiological, and loss of work hours, reduced productivity, chronobiological characteristics to adapt to increased work errors and impaired social work at unusual hours. and family relationship. In addition, there is an increased mortality risk when sleepiness Optimize activity-rest schedules and affects motor vehicle and train drivers, maintain adequate levels of vigilance and aircraft pilots, nuclear power workers, and, performance. generally, people involved in crucial occupations (e.g. Mittler, Carskadon, Schedules implying night shifts and/or Czeisler, Dement, Dinges, Curtis, Graeber, fragmentation of duty periods throughout 1988). the 24-hr day require meeting sleep need at Military operations are often characterized different moments of the 24-hr continuum, by prolonged periods of wakefulness; until uninterrupted 8-hr sleep is possible. In irregular rest-activity patterns; long haul such conditions, polyphasic sleep-wake flights. These situations are unnatural. strategies have potential practical Severe sleep debt can accumulate, leading to applications. Sleep behaviour is considered dangerous levels of sleepiness and decreases polyphasic if less than 50% of total sleep of performance, which become evident after time is obtained in one continuous episode. 24 hrs of sleep deprivation. In such a situation, multiple naps and In addition, personnel involved in periods of wakefulness alternate throughout sustained/irregular operations are often a 24-hr period (Stampi, 1992a). A large unable to recognize and counteract fatigue number of laboratory and field studies and decreased performance. This condition suggest that humans engaged in different can be due to: a) a discrepancy between types of polyphasic schedules can easily subjective and objective decrease of adapt to multiple napping regimens. It has vigilance; b) a tendency to underestimate been reported that some subjects can be able fatigue; c) inadequate shift schedules; d) to reduce sleep to an average of less than 3 scarce attention to selecting people able to hours per day, up to 2 months. These were sustain prolonged wakefulness and/or divided into 6 naps of 30 minutes each, one unusual sleep-wake rhythlms. every 4 hours. Contrary to the usual To maintain high levels of performance findings of sleep deprivation experiments, in during sustained operation and/or irregular which only part of REM and stage 2 sleep, 21-1 Paper presented at the RTO HFM Workshop on "Individual Differences in the Adaptability to Irregular Rest-Work Rhythms/Status of the Use of Drugs in Sleep-Wakefulness Management", held in Venice, Italy, 3-4 June 1999, and published in RTO MP-31.
21-2 but not SWS amount are penalized, all sleep Thus, results of this study confirm that it is stages were proportionately reduced. This easy to break the usual monophasic sleep was probably due to the very long duration efficiency and to adapt to a complicated of the study (Stampi, 1992b). regimen, alternating 24 hrs of an usual rest- With regard to performance, preliminary activity cycle with a nocturnal monophasic data seem to show that individuals under sleep and 24 hrs of a polyphasic pattern. polyphasic and ultrashort sleep schedules However, these data do not allow to draw can function at levels equal to, or higher any conclusion about performance, since it than, when they were under a comparable was not evaluated in the present study. The amount of monophasic sleep (Stampi, great reduction of sleep duration did not 1992c). It appears that polyphasic sleep- cause any evident decrease of vigilance, as wake schedules are a viable solution in defined by the occurrence of microsleeps, oreder to maintain high levels of efficiency but we cannot exclude that the very great during continuous work situations. sleep loss also did not cause detrimental For the armed defence service on air bases, effects on performance. Whether future the Italian Air Force adopts, an unusual research will prove that adult humans can work schedule, characterized by 24-hrs on adapt to this schedule with no significant duty followed by a day off duty. The day on decrease of performance, this alternating duty is characterized by 4 rest-activity monophasic-polyphasic regimen should be a cycles repeated throughout the day. Each suitable strategy for the management of cycle is of 2-hrs of activity and 4-hrs of rest continuous operations. (sleep allowed). In a previous study (Porcii, Casagrande, Select people with the most useful Ferrara, Bellatreccia, 1998) Italian armed psychological, psychophysiological, and defence personnel were monitored by means chronobiological characteristics to adapt of ambulatory polyson-ography while to work at unusual hours. attending their 24-hr rest-activity schedule. Sleep periods were visually scored Although sleep deprivation, time of day and according to standard criteria. Wake periods time on task are considered among the most were visually scored using both 30 sec and important causal factors of daytime 5 sec epochs in order to reveal episodes of sleepiness (e.g. Akerstedt and Kecklund, drowsiness and/or microsleep. Results 1994), the levels of vigilance may still showed that total sleep time was significantly vary according to individual substantially reduced as compared to the differences. Some individual characteristics usual 7-8 hour monophasic nocturnal sleep. contribute, in fact, in modulating general Subjects did not sleep during the first rest levels and time of day effects of vigilance, period (11.00-15.00). Time in sleep linearly sleepiness and performance and modulate increased in the course of the 3 remaining even the intensity with which the various rest periods. Normal sleep structure was deactivating factors individually act (e.g. anyway substantially maintained. SWS and Akerstedt and Torsvall, 1981; Harma, REM sleep were mostly expressed, 1993). respectively, in the first (3rd rest cycle: 9.00 Verifying whether and to what extent some p.m. - 1.00 a.m.) and in the last (4th rest stable individual differences are associated cycle: 3.00-7.00 a.m.) third of the night, to specific variations of vigilance and maintaining their owan natural circadian performance may be important in orienting rhythm. the best criteria for the selection of In addition, our results indicate that this personnel involved in particular types of rest-activity schedule, despite the professions requiring shift work, prolonged considerable sleep reduction, allowed activity for many hours or unusual hours, maintaining good levels of vigilance as and/or monotonous activity. shownvi by the virtual absence of EEG Poor attention has been paid to such microsleeps. important factors as the individual ones. In
fact, there is a surprising lack of studies on d) each country might add original individual differences in the adaptability to contributions to the project, integrating the irregular sleep-wake rhythms. "core project Many factors have contributed to this Here follows a summary of a research condition. Studies on individual differences project, which we propose to carry out on are necessarily long, time consuming and personnel working on polyphasic-rest require a large sample size. activity schedules, in order to address the To find out which individual characteristics above issues. can garantee the best adaptability to sustained operations and to irregular or Research project. unusual rest-activity schedules, it is essential to define: Subiect inclusion criteria a) Which physiological, behavioral and/or Healthy males psychological parameters are useful to - Age: 18-40 years old define the "adaptability dimension". No sleep disorders in the anamnesis b) Which individual traits can allow us to No previous significant shiftpredict adequate adaptability, work/irregular sleep-wake experience To evaluate both the "adaptability * No drugs/alcohol construct" and the "individual traits", it is Nonral lifestyle necessary to take into account a very large number of variables: psychological, Experimental desian subjective, behavioral, The project is divided into 4 phases: physiological/biological, * Phase one, immediately before the psychophysiological, chronobiological. beginning of the polyphasic activity, to be It is also necessary to use a multivariate carried out in the lab; statistical approach: Phase two and three, during the polyphasic a) Factor Analysis, Discriminant Analysis, activity, to be carried out "in the field"; and/or Cluster Analysis to single out the Phase four, during the polyphasic activity, parameters (and their weight) that to be carried out in the lab on subjects with contribute to define the "adaptability extreme individual characteristics, selected construct"; on the basis of the results of the three b) Multiple Regression Analysis to evaluate previous phases. the predictors of adaptability; c) Multivariate Regression Analysis for PHASE 1 (Before the polyphasic activit)) evaluating the specific contribution of several "predictors" (independent variables) a) Questionnaires will be used to on several "criteria" (dependent variables), evaluate of the following individual To carry out such statistical analysis it is traits: necessary to have a huge subject sample. It is estimated that about 12 observations are Sleepiness: Epworth Sleepiness Scale needed for each considered variable. (ESS, Jolns, 1991); Studies of this size can hardly be carried out * Circadian Typology: Morningnessby a single laboratory. A multicentric Eveningness Questionnaire (Home & approach is necessary: Ostberg, 1976); a) several laboratories (nations) should Extroversion, Neuroticism, Psychoticism: participate to a common "core project; Evsenck Personality Inventory (EPI, b) the same experimental design should be Eysenck, 1967); followed in each laboratory; - Coping Strategies: Coping Inventory for c) the subject sample size should be shared Stressful Situations (CISS, Endler e by the participants; Parker, 1990); 21-3
21-4 "* Sleep, Vigilance and Sleep-Wake Cycle Photostimulation: blind counterbalanced Characteristics (Questionnaire by the Italian administration of bright and dim light as Air Force). follows: 10 min stimulation after each of the 4 rest b) Laboratory evaluation of: periods (iimnediately before working); Standard polygrafic recordings of sleep for 30 min stimulation at the end of the two nights; working day (i.e. in the morning of the day - Diurnal and nocturnal administrations of off duty). MSLT and MWT; 0 Diurnal and nocturnal repeated PHASE 3 (After 6 months of polyphasic assessments of vigilance, performance and activity) mood (mainly by means of EEG measures, The same experimental design as in PHASE "pencil-and-paper" and/or computerized 2 will be followed, in order to assess task; possible changes in the considered variables due to an improved adaptation to the c) Biolo2ical parameter assessment: irregular rest-work schedule Multiple salivary samples to evaluate melatonin and cortisol rhythms; PHASE 4 (After 8 months of polyphasic 0 Continuous recording of body activit) temperature; The same experimental design as in PHASE 0 Multiple blood samples to evaluate 1 will be followed, on groups of subjects parasympathetic and orthosympathetic selected for their "extreme" characteristics hormones, as well as lymphocyte of adaptability to the irregular rest-work benzodiazepine receptors; schedule (i.e. the best and worst adapted - EKG recording and heart rate spectral subjects). analysis; REFERENCES PHASE 2 (After 1 month of polyphasic activit.) Akerstedt T, Kecklund G (1994) Work "In the field" recordings, 4 consecutive days hours & sleepiness. In: Akerstedt T, (2 days on duty, 2 days off duty): Kecklund G. Work hours, sleepiness and " Ambulatory polysoinography (96 hrs); accidents. Stress Research Reports, "* Reaction Time Task to weak vibratory Stockholm; 248: 13-17. stimuli (96 hrs); Akerstedt T., Torsvall L (1981) Shiftwork: - Letter Cancellation Tasks (Casagrande, shift-dependent well-being and individual Violani, Curcio, Bertini, 1997) and differences. Ergonomics 24: 265-273. subjective evaluations of mood and alertness Casagrande M, Violani C, Curcio G, Bertini as follows: M (1997) Assessing vigilance through a * DAY ON DUTY: before and after each brief pencil Letter Cancellation Task (LCT): rest period; effects of one night of sleep deprivation and 0 DAY OFF DUTY: upon morning of the time of day. Ergonomics. 40 (6): 613- awakening, at the same time of the day on 630. duty, immediately before "lights off'; Endler NS, Parker JD (1990) " Sleep logs as follows: Multidimensional assessment of coping: A "* DAY ON DUTY: a brief questionnaire on critical evaluation. Journal of Personality the sleep-wake cycle and vigilance filled in and Social Psychology. 58: 844-854. after each of the 4 rest periods;; Eysenck H (1967) The biological basis of - DAY OFF DUTY: a brief questionnaire personality Thomas, Sringfield. on the sleep-wake cycle and vigilance filled Hanna M (1993) Individual differences in in upon morning awakening. tolerance to shift-work, Ergonomics 36: 101-109.
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