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Yeo Wei Jie Yeo Whee Lim Shabbir Moochhala Introduction



                            Yeo Wei Jie1, Yeo Whee Lim2, Shabbir Moochhala2


    When humans are acutely exposed to sleep deprivation, cognitive performance is substantially degraded.
About 5% of the Asian population suffers from parasomnias. About 90% of these are psychologically induced
while the remaining 10% are due to aging central nervous systems. The aim of this scope of work was to
evaluate the latency of sleep deprivation on the local students’ concentration flexes, decision-making and
perceptual speed. Two in-house cognitive performance evaluation systems, namely the Swedish Performance
Evaluation System (SPES) and Walter Reed Performance Assessment Battery (WRPAB) were used. The study
population comprised of 16 students parametrically divided evenly into a mildly sleep-deprived (1 to 3 hours
less than their norm) group (n=8) and a control or non-sleep deprived group (n=8) for the research pilot study.
The pilot study showed that the mean choice reaction time (CRT) of these sleep-deprived (mean
CRT=555.13±111.91) students was prolonged by a further 9.3% versus the control group (mean
CRT=508.00±34.05). Statistically proven, mild sleep deprivation significantly impacted the students’ decision-
making choice reaction cognitive responses compared to the control group using SPES test battery (F=3.64,
df=14, P<0.05). Although similar trends were observed for the concentration reflexes and perceptual speed for
the sleep-deprived group compared to the control group, this difference was not significant (p>0.05). No such
significance was pick-up using the WRPAB. It was also found that caffeine (1,3,7 trimethylxanthine) an
ergogenic or performance-enhancing aid could be used to help improve the concentration, alertness and
vigilance cognitive performance of sleep-deprived students. Conclusively, students should not be sleep-
deprived for more than 3 hours and should avoid any phasic shift in circadian rhythms the night before if they
are going to be involved in decision-making performance tasks the following day.

                                               1. Introduction
    Vertebrate and invertebrate primates with a developed central and autonomic nervous system have an
endogenous biological clock regulated by a circadian pacemaker to counter balance the stressors of all forms
of fatigue and other stress-induced homeostatic mechanisms. This effect is in sync with the exogenous light-
dark cycle being controlled by the earth’s rotational effects and is ubiquitously experienced by all living
primates worldwide. This biological effect is known as sleep or rest circadian rhythm. Musical harmonics
seems in good allianz with sleep and can be used in combination with homeopathic and naturopathic therapies
to relief tension. In higher order mammals like humans, this biological rhythm is essential for general well
being of all individuals and indirectly affects tasks performance of students and military personnel. Regulating
or pharmacologically modulating circadian rhythms without affecting the performance of individuals is one of
the golden keys of military commanders in planning offensive warfare-defensive deployment activities for our
SAF troops. Students who are unaffected by sleep deprivation would also have an academic competitive edge
over their counterpart rivals. Notably, circadian rhythms are only a function of the age and affects all ethnic

    Sleep has also been referred to a state of periodic, voluntary loss of consciousness which is termed ‘sleep’.
Most people spend about 7 to 8 hours per day in this biological subconscious state. By the time we have reach
the age of 60 to 70, most of us have spent approximately 20 years of sleep in relative oblivion. The number of
hours of sleep required depends on the age of the individual, newborns require 15 to 16 hours while
adolescence and young adults should feel comfortable with 7 to 8 and elderly individuals require 9 to 10 hours
to feel adequate. For this reason alone, sleep would seem to be pertinent and inconsequential, although
explanations as to why we do it remain in dispute [4].

 Science Research Programme Student, Raffles Junior College
 Combat Care and Performance Laboratory, Defence Medical Research Institute,
Defence Science and Technology Agency
    Sleep certainly does appear to be central to medical practice, since complaints about inadequate,
unrefreshing or disturbed sleep are a frequent cause of people seeking help. In most medical cases, sleep does
have a therapeutic or prophylactic effect on convalescing patients. It is general knowledge that sleep is
synonymous with rest. Any spatial or non-spatial perturbations to influence the quality of sleep, would affect
the mood, fatigue, stress and ultimately the tasks performance of healthy and unhealthy individuals. According
to an estimate, about one in ten nights’ sleep of adults in the United Kingdom is induced pharmacologically.
However, this mild deprivation has not been evaluated in the Asian student population. This pilot study seeks
to identify or siphon out mild sleep deprived individuals at risk to cognitive performance degradation as a
screening tests for pre-enlistees for the tri-service armed forces. This versatile and easy to carry out prognostic
and surrogate tool would equip commanders with a yardstick when assigning soldiers to appropriate vocations.

                        1.1 The medical physiology and chronobiology of normal sleep
    Psychophysiological studies of sleep are surrogately employed by medical professionals as well as
researchers to prognosticate sleep parasomnias. The methodology employed is usually approached by
recording the EEG from electrodes placed over the frontal and occipital cortex (C3-A2, C4-A1), from other
placed alongside the LOC and ROC eyes and yet others placed below the chin (EMG 1 and EMG2). Other
feasible methods include polysomnography using actigraphy to track movement during the sleep. The sleep of
a healthy, young adult (18-25 years) displays a characteristic profile. Anatomically, the brain development
maturity should climax by the age of 15-16 for both males and females. Following conventional scales of sleep
depth, determined by the frequency and amplitude of the EEG, there is a rapid ‘descent’ from the alpha
patterns (12-14 Hz, low voltage) which is characteristic of relaxed wakefulness, to ‘delta’ activity (2-4 Hz,
high voltage) normally associated with profound loss of consciousness. Approximately once every 90 minutes
there is a remarkable change in the EEG which then displays evidence of strong activation, placing this kind of
sleep close to wakefulness in physiological terms. This state is accompanied by bursts of rapid, jerky eye
movements, increased brain temperature and blood flow, secretion of catecholamines, marked lability of blood
pressure, heart rate, respiration rate, twitching of the extremities (fingers and toes) and a general loss of muscle
tonus apart from in those needed to maintain life. This kind of sleep is the now well-known Rapid Eye
Movement (REM) phase of sleep with which dreaming is associated. REM episodes become longer and more
physiologically intense as the night progresses, and dreams correspondingly become more vivid.

    Young adults spend around 25% of their sleep in REM and another quarter in delta-wave sleep, also
known as slow wave sleep (SWS) or sometimes as ‘deep’ sleep. The remaining 50% is spent in a stage
intermediate between these two. There are needs for REM and SWS demonstrated by the fact that deprivation
of either one of them by deliberate, laboratory experimentation or by pharmacological and environmental
demands, results in a ‘rebound’ phenomenon, whereby an attempt is made to regain the lost sleep when
allowed to sleep naturally [4].

           1.2 Sleep as a physiological and psychological mechanism to rejuvenate and revitalize
     Whenever sleep is deprived or phase comprised or there is an over-exertion of one’s physical strength,
humans tend to homeostically respond via autogenic feedback mechanisms by showing symptoms of fatigue
and sleepiness. This biological effect can be quenched by taking naps or microsleeps to complete the segments
or cycles of sleep loss. Most individuals need 8 hours of sleep cycles per night, and will often complain if this
perceived need goes unmet. While it is true that the average need lies around 7.5 to 8 hours per day, there is
variation around this mean depending on the age of the individual. Irregular sleep architectures may lead the
naturally short sleeper to seek and become dependent on pharmacologically aids to boost up sleep loss. The
naturally long sleeper on a ration of eight hours may end up in a pseudochronically sleep-deprived state
although this effect is easily desensitized by subjecting the individual to prolonged periods of reduced sleep

                                    1..3 Acute and Chronic Sleep Deprivation
     Students do not regularly experience total sleep loss. More often they undergo partial sleep loss. For the
average person who sleeps around 8 hours per night, cognitive functioning does not seem to be impaired until
less than 2 hours’ sleep have been achieved on any one night.
    However, if the sleeper is going to undergo a prolonged period of reduced sleep, then the evidence
suggests that there is a minimum need for at least 6 hours per night. However, soldiers keeping vigil during
wartimes could experience long hours of total sleep deprivation. Consequences of sleep loss or parasomnias
could arise when subjected to prolonged periods of insufficient sleep. The perils of other complications could
surface or existing ailments could recur. Hallucinations can occur incases of total sleep deprivation. Shorter
periods of total sleep loss are associated with lowered arousal levels during the following day which are
manifested in periods of inability to maintain concentration interspersed between normal periods of normal
functioning. Decision-making and perceptual speed reflexes during all tasks performances are also
compromised. The inability to sustain concentration, alertness and vigilance is more evident during the
morning hours than the late afternoon, probably because of increasing arousal levels as the day progresses.
Sleep loss may also be accompanied by an increase in ‘microsleeps’ which are very brief periods when
individuals seem incapable of registering input or focusing attention. Naturally, undertaking hazardous
activities such as driving vehicles while in this state can be dangerous.

                                                      2. Aim
    The specific aim was to investigate the latency of mild sleep deprivation (about 1-3 hours less than usual),
which is fairly common among JC students due to their busy and hectic schedules, as a function of the
students’ reflexes of concentration, decision-making and perceptual speed cognitive responses. It has been
established by the US Army reported that for more pronounced effect, at least greater than 48 hour continuous
deprivation would yield obvious performance degradation [4].

                                           3. Materials and Methods
    A total of 16 JC1 all chinese students with above average intelligent quotient, emotional quotient and
normal sleep-wake circadian rhythm participated in the research study. The design methodology was tailored
to two groups. The control or placebo group comprised of 8 students who slept their usual or more number of
hours which did not exceed greater than 4hrs. The test or experimental group comprised of 8 different students
who suffered mild sleep deprivation by sleeping about 1-3 hours less than their norm which did not exceed less
than 4 hrs. Latency in the two groups was evaluated by concentration, decision-making and perceptual speed
cognitive responses. Two in-house psychological assessment test batteries namely SPES and WRPAB were
used as evaluation systems. The total testing time was approximately 30-40 minutes and comprised of 5
regular intervals for 6 modular tests. These included ‘Wilkinson Serial Reaction Time’(WSRT), ‘Choice
Reaction Time’(WRCRT) and ‘Matching to Sample’(WRMS) were used from the Walter Reed Performance
Assessment Battery while ‘Simple Reaction Time’(SRT), ‘Choice Reaction Time’(CRT) and ‘Digit-Symbol
Matching’(DM) were chosen from the Swedish Performance Evaluation System for the research study
[1,2].Following are short descriptions of the respective SPES tests used in the research study. Descriptions of
the WRPAB tests have not been included as they are tandem repeats of the tests used in SPES.

     3.1 SRT (equivalent of WSRT) The task was to press a key on the keyboard as quickly as possible when a
white square was presented on the display. A total of 96 stimuli were administered during 6 min at intervals
varying between 2.5 and 5.0 s. The first minute served as practice, after which performance capacity was
assessed for 5 min. This module cognitive responses essentially tests subjects’ concentration and alertness
reflexes [1].

    3.2 CRT (equivalent of WRCRT) A four-choice reaction time task similar to SRT with the addition of
response selection requirements. The stimuli consisted of crosses displayed one at a time on the screen. One
arm of the cross was always shorter, and the task was to indicate on one of four keys, placed in analogy to the
arms of the cross, which arm was the shorter. A total of 144 stimuli were presented at the same intervals as in
Simple reaction time and the first two minutes were excluded as practice trials. This module cognitive
responses essentially tests subjects’ decision-making and tasks execution ability [1].

    3.3 DSM (equivalent of WRMS) A revised version of a traditional test of perceptual speed. In one row a
key to this coding task is given by the pairing of symbols with the randomly arranged digits 1 to 9.
     The task was to key in as fast as possible the digits corresponding to the symbols presented in random
order in a second row. Each item consisted of 9 pairs of randomly arranged symbols and digits, and a total of
ten items were presented. Performance was evaluated for the last six items of the test [1].

    3.4 Sleep Questionnaire Survey Sampling (SQSS) [Refer to Appendix A].

                                          4. Results and Discussion
   4.1.Statistical Analysis SPSS Version 12 was used for the statistical data analysis. The signification value
was set at p<0.05. Independent t-test was used when comparison of the groups were of similar strength.

    4.2 Characteristics of student study population The mean no of hours slept was 7 hours. 25.1% (n=16)
were in a positive good mood during the test while the remainder 74.9% (n=16) are either in a negative mood
or were ambivalent about their moods. It was reported that 37.5% (n=16) of the students were not fatigue
while the remainder 62.5%(n=16) reported somewhat fatigue status (Table1).

                             Table 1. Characteristics of Student Study Population

                Population Study          Age (years)          Height (m)          Weight (kg)
                 Demographics             (Mean+SD)            (Mean+SD)           (Mean+SD)

           Total (n=16)                    16.31+0.48           1.73+0.06           60.88+7.62
           Control (n=8)                   16.25+0.46           1.74+0.57           59.13+8.27
           Sleep Deprived (n=8)            16.38±0.518          1.71±0.73           62.63±6.99

    4.3 Effect of sleep deprivation on student concentration, decision-making and perceptual speed.

      Table 2. Concentration, Decision-making and Perceptual Speed Cognitive Responses of students
                             among Sleep-deprived versus Control group

                                Mean Reaction Time (Mean ms+SD)

         SPES                  Sleep-deprived               Control                P-Value Significanceª
                                    (n=8)                     (n=8)
Simple Reaction Time            277.75±23.50              262.25±15.32           F=2.18, df=14, 0.1<P<0.2

Digit-Symbol Matching         1954.25±317.74             1827.13±119.60         F=14.4, df=14, 0.05<p<0.1

Choice Reaction Time           555.13±111.91              508.00±34.05            F=3.64, df=14, P<0.05

                             ª Figures calculated using the Independent Samples T Test

     While differences observed between the results for the sleep-deprived and control groups for the WRPAB
tests were not significant, significant results were obtained for only for Choice Reaction Time SPES tests
(f=3.64, df=14, p<0.05). For all three SPES tests, it was consistently found that the sleep-deprived group did
indeed take a longer time, on average, to react correctly to the stimuli than the control group. The greatest
difference in the mean reaction time taken was observed for the CRT test, with the sleep-deprived group
taking, on average, 555.13 ms to respond correctly to each stimuli, compared to the control group taking only,
on average, 508.00 ms to respond correctly to each stimuli. From the results encountered the SPES tests have
been found to be more reproducible and have much higher test-retest reliability ratios. The SPES have been
used as a diagnostic tool in the COFM to prognosticate pathophysiological conditions like Chronic Fatigue
Syndrome. Meanwhile, the results obtained also conclusively showed that mild sleep deprivation does have a
noticeable impact on concentration, decision-making and perceptual speed in students, with the sleep-deprived
group having a greater mean reaction time than the control group for all three SPES tests (Table 2 and Chart
1) [3,5].
      Chart 1. Concentration, Decision-making and Perceptual Speed Cognitive Responses of students
                               among Sleep-deprived versus Control group

                                   Effects of sleep on cognitive abilities using SPES test battery.
                                      Sleep Deprived subjects (n=8) vs Control subjects (n=8)
                                                                               Sleep Deprived

                      MEAN Scores of time for correct
                                                  2000                         Control

                        responses (milliseconds)

                                                  1000                                   *p<0.05

                                                                    SRT                         CRT                     DM
                                                                           Chart 1 Cognition Test Modules
                                                                  SRT:Serial Reaction Time, CRT:Choice Reaction Time,
                                                                               DM:Digit Symbol Matching

    4.4 Effect of sleep deprived individuals who consume caffeinated beverages

                     Table 3. Effect of Caffeine on Perceptual Speed and Decision-making
                                         among sleep-deprived students

                                                                       Mean Reaction Time (ms)

           SPES/WRCRT                                                 Caffeine
                                                                                            (non-caffeine           P Value Significanceª
                                                                        (n=4)                   (n=4)

    Digit-Symbol Matching                                          1784.00±89.30           1916.25±176.25         F=4.07, df=6, 0.05<p<0.1

    Walter-Reed CRT                                                301.75+85.48                 296.5+25.05         F=15.15, df=6, p<0.05

                                                              ª Figures calculated using the Independent Samples T Test

     In a comparison of results between sleep-deprived individuals who took caffeine prior to the cognition
tests and sleep-deprived individuals who did not do so, differences were observed for the digit-symbol
matching between the caffeine drinkers and the control group. Caffeine did have an effect of improving the
perceptual speed of students who participated. However, this difference is not significant. It was interesting to
mention that for the WRCRT, the non-caffeine drinkers seem to be able to make decisions significantly better
than the caffeine drinkers (F=15.15, df=6, p<0.05). However the mechanism of this is unknown. Caffeine as a
psychostimulant is widely regarded by many to be capable of improving one’s concentration, alertness and
vigilance. However, the medicinal value of it is controversial as not all individuals are sensitize to the effects
of caffeine.
    4.5 Effect of mood profiles on concentration

                           Table 4. Effect of Mood on the Concentration of students

                                               Mean Reaction Time (ms)

               Walter Reed                   Bad Mood           Good Mood           P Value Significanceª
                                               (n=5)              (n=5)

    Wilkinson Serial Reaction Time          425.60±84.09        367.40±33.87        F=5.48, df=8, p<0.05
                                  ª Figures calculated using the Independent Samples T Test

     Meanwhile, between the students who were in a bad mood (described their mood with words such as
‘irritated’, ‘worried’ and ‘unhappy’) and those who were in a good mood (described their mood with words
such as ‘jovial’ and ‘happy’) on the day of the cognition tests, significant differences were also observed for
the WSRT test. It was found that those in a bad mood took a longer time to react correctly to the stimuli, with
a mean reaction time of 425.60 ms, compared to those in a good mood who only took 367.40 ms, on average.
All other cognitive test modules were not significantly affected by mood changes of the students.

     4.6 Effect of fatigue on sleep deprivation
     Meanwhile, the results also showed that fatigued did have an effect on the sleep-deprived group (those
who rated themselves from 4 to 7 on the scale for their fatigue level on the day of the cognition tests) when
you ran the ‘Digit-Symbol Matching (DM)’ test (u= 1, p<0.05 ß). In other words, it was found that if you were
fatigued and sleep-deprived, you would perform worse than if you were fatigued but not sleep-deprived.
Fatigue significantly impacted the perceptual speed of sleep deprived individuals.

    1.5.5 Effect of Biological and Ultradian Rhythms on cognition testing
    Lastly, we also found that endogenous biological rhythms did not affect cognition tests based on these two
performance evaluation systems. The time of day at which the tests were done did not seem to affect the
subjects’ performance based on the results obtained in our research study.

    The SPES test was a more sensitive, specific and reliable psychological tests battery for cognitive
assessment of students’ concentration, decision-making and perceptual speed. Conclusively, students should
not be sleep-deprived for more than 3 hours and should avoid any phasic shift in circadian rhythms the night
before if they are going to be involved in decision-making performance tasks the following day. This test
battery has been used for anti-aging studies by the Obstetrics & Gynaecology Department, NUH as well as for
the study of Chronic Fatigue Syndrome. This cognitive test battery has also been validated for used in the field
on board patrol vessels. As the test battery was relatively easy to use, the learning curve effect could be easily
[1] F.Gamberale, A.Iregren and A.Kjellberg, The Swedish Performance Evaluation System,
       Neuroroxicology and Teratology, 1996, Vol 18(4), p485-p491
[2] D.R. Thorne, S.G. Genser and H.C. Sing and F.W. Hegge, The Walter Reed Performance Assessment
       Battery, Nerobahvioural Toxicology and Teratology, 1985, Vol 7, p415-418
[3] S.P.A. Drummond and G.B. Brown, The Effects of Total Sleep Deprivation on Cerebral Responses to
       Cognitive Performance, Neuropsychopharmacology, 2001, Vol 26, S68-S73
[4] M. Herbert, Sleep, Circadian Rhythms and Health, 1994, p165-167

We would like to express our sincere gratitude to all participated RJC year 1 students who diligently
and conscientiously contributed to the data collection exercise. I would also like to thank Jenny Tan Y.F.
SRP coordinator from DSTA-HR, the teacher-in-charge of the SRP students and Prof Shabbir
Moochhala for allowing us to use the CCPL premise for this project. All other individuals including
mentors who have contributed substantially in one way or another to this pilot study.
                                                 Appendix A
   1. Are you currently aware that you are taking part in a sleep cognition research programme conducted
       by a joint collaborative effort by DSTA and RJC?
   2. Has the conduct of the study been thoroughly explained by the administrator of the cognitive modules?
   3. How would you describe your personality? (Please use four adjectives that best describes you)
   4. Do you dream or remember your dreams when you wake up?
   5. Do you have any nightmares or experienced interrupted sleep during the past 1-month?
   6. Do you have any difficulty falling asleep or have any waking-up problems?
   7. (a)Do you have any past medical history of any sleeping problems? If so, please provide details (b)Do
       you take medications to solve any insomnia problems? If so, please provide details
   8. Do you consume any caffeine-related beverages or compounds seven days before the day of the
       cognition tests?
   9. What position do you adopt when you are in the supine position on the bed before you sleep? (Face-
       up, face-down or Face-left or Face-right)
   10. Do you have the habit of consuming foodstuffs six hours prior to bedding time?
   11. How would you describe your mood on the day of the cognitive tests?
   12. Have you ever been sleep deprived during the past 1 month? If so, how would you rate your mood the
       next day after you are awake? How would you rate your performance?
   13. Have your ever slept excessively each day (> 8 hours) during the past 1 month? Describe your mood
       and performance the next day.
   14. In your own opinion, what do you feel is the most appropriate no of hours of sleep? What would
       qualify as a “long sleeper” and “short sleeper” based on the number of hours of sleep?
   15. Do you listen to music when you sleep?
   16. How would you rate your fatigue-level on the day of the cognition tests?
       (1=Fully alert, wide awake; 2=very lively, responsive, but not at peak, 3=okay somewhat fresh; 4=a
       little tired, less than fresh ; 5=moderately tired, let down; 6=extremely tired, very difficult to
       concentrate, 7=completely exhausted, unable to function effectively)
   17. How would you rate your ability to concentrate on the day of your cognition tests?

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