RICERCA ITALIANA     

Research program

Sleep-debt effects on procedural learning and on clinical and cognitive performance in resident physicians: the protective function of naps

University Co-ordinator

Seconda Università degli Studi di NAPOLI - PSICOLOGIA - ()

Research Unit Leader

Gianluca Ficca

Description

For what previously said in the "background" chapter, the present research is aimed: a) to investigate whether and to what extent sleep loss might affect superior executive functions during prolonged work shift of junior resident doctors and b) to determine whether specific napping strategies can modulate this influence.
PARTICIPANTS
The project the Unit at the Department of Psychology of the University of Napoli consists of experimental sessions on 200 junior doctors (M=100, F=100), without sleep disorders and any medical diseases affecting sleep and alertness.
Participants will be recruited from the population of the residency schools of the two Faculties of Medicine and Surgery of the University of Napoli among those available to take part in a 64-h “on the field” study. Half of the subjects will be expert residents (4th year of study), while the other half will be selected during the 2nd year of post-graduate program.
Participants will be right-handed, 26 to 32 years old, and without sleep disorders (QDS, [35]), with an intermediate circadian sleep quality (MEQ, [21]), without cognitive, motor or perceptual disorders and not pharmacologically treated for any medically relevant disease. Subjects will be requested to keep a regular wake/sleep rhythm in the week before and in the one after the experimental session and to compile an ad-hoc sleep diary provided by researchers.
A preliminary psychophysical assessment will be carried out to exclude any transitory clinical affection.
All subjects will be informed about the general aims of the study and will sign an informed consent before entering the experimental routine.

PROCEDURE
The selected sample of young doctors will be subdivided in 10 experimental groups, each including 20 participants routinely involved in "on-call" duty and night shift (matched for age, gender and expertise level). The complete experimental protocol is reported in the scheme below.

According to the experimental design (the same adopted by the other research units involved in the general project), the sample will be subdivided in 10 subgroups. Briefly, the 2 “Control” subgroups (A and B) will regularly sleep at home both in Night 1 and 2, being monitored by actigraph, while the other 8 subgroups (nightwork subgroups) will be involved in on-call or night shift duties under the control of senior doctors, which will have an explicit function of tutor for the activities of the young doctors.
Two of the 8 “experimental” subgroups (respectively C and D) will remain awake over the night and over the following day, namely without the possibility of taking any night- or day-time nap; two other subgroups (respectively E and F) will take a nap, between 2 and 5 a.m., not longer than 45 minutes, whenever decided by each subject according to his/her subjectively estimated sleepiness and to concomitant medical work needs; two other subgroups (respectively G and H) will take a nightime nap like participants of E and F subgroups and a second daytime nap not longer than 45 minutes at about 2 p.m; two other subgroups (respectively I and L) will remain awake over the night and will take a daytime nap not longer than 45 minutes at about 2 p.m.
During both afternoon and night naps, subjects will undergo conventional polysomnography (EEG, EOG, EMG) by means of an ambulatory polygraphic system. Polysomnographic tracings will allow to analyse the duration and the structure of each nap.
Furthermore, all participants will wear continuously an actigraph on the nondominant wrist from the night preceding Day 1 until Day 3 (including the two intermediate nights) to retrospectively identify the presence of unintended naps or microsleep episodes. Participants with unintended naps or more than 2 microsleep episodes (shorter than 5 min) will be excluded from statistical analyses and replaced by other residents.

As for neuropsychological testing, these will be carried, through ordinary laptops, in quiet rooms of the hospital where junior residents attend their clinical and didactic duties.

Objective measures
Participants will be engaged in two tasks, one to be carried out in the day 1, 3 and 8, and the other one in the day 2, 3 and 8. The two tasks will be administered according to two distinct schedules to ascertain a) by means of the former schedule, the effect of post-training sleep deprivation (tempered or not by one or two naps) due to a working night on the further consolidation of the specific procedural skills involved in that task; b) by means of the latter, the effect of sleep deprivation on the acquisition and consolidation of task-specific procedural skills according to whether the sleep loss is or is not tempered by one (at night /in the afternoon) or two naps no longer than 45 minutes.
Each subgroup of participants included in the sample will be assigned to either task condition, namely Wisconsin Card Sorting Test (WCST) or to Random Letter Generation (RLG) to be performed once in the Day 1, the other task having to be carried out once or twice (according to the experimental design described) in the Day 2. Therefore, 5 subgroups (A, C, E, G, I) will be tested on WCST in days 1, 3 and 8, and on RLG in days 2 (once or twice), 3 and 8, always from 11 to 12 a.m. (except for re-test of RLG at 4 p.m. for half of the participants of each subgroup, again randomly selected).
The other 5 subgroups (B, D, F, H, L) will be tested on RLG in days 1, 3 and 8, and on WCST in days 2 (once or twice: see below), 3 and 8, always from 11 to 12 a.m. (except for re-test of WCST at 4 p.m. for half of the participants of each subgroup, again randomly selected). The complete picture of the measures obtained should allow to distinguish the possible different restorative effect of afternoon nap from that of night 2 (spent at home by all participants), namely after one night of recovery sleep (monitored by actigraph), with respect to the complex executive functions taken into account.
The test selected, that are briefly described below, have been chosen according to their validity and reliability, on one hand, but also because they are rapid and easy to administer. Thus, they are feasible even in "on field" settings, where it is strictly required not to interfere too much with routine activities.

WISCONSIN CARD SORTING TEST (Berg, 1948)
This is a test used to examine frontal executive functions, namely to address flexibility in choosing action strategies in "problem solving" processes and to detect possible perseverations and deficits in abstract thinking.
The test is based on the administration of 128 cards ("response cards"), each containing from one to four identical figures (stars, crosses, triangles, circles) of a single colour among four (red, yellow, blue, green).(e.g., a single card might contain four green triangles or two yellow circles).
response cards are given to the subjects while instructing him to put them below four "guide cards" (respectively displaying a red triangle, two green stars, three yellow crosses and four blue circles), lying in front of him, according to a criterion previously decided by the experimenter and not revealed to the subject.
Thus, the individual has to understand the hidden criterion when he starts to arrange the cards and gets information about whether what he has done is right or wrong.
First category to be followed is the colour, then, after ten consecutive right answers, it's the turn of the shape, and finally come the number. The whole cycle has to be repeated twice, for a total series of six completed categories.
Amongst the different kind of possible mistakes, it is very important to focus on subject's perseverations, occuring whenever an answer is given according to a criterion previously used but just replaced by a new one.

RANDOM LETTER GENERATION (Sagaspe et al., 2003; Heuer et al., 2005)
The Random Letter Generation Task is about two minutes in length and consists in verbally producing a sequence of 100 letters in a random fashion. This kind of sequences may be produced by the subject only by inhibiting, through the engagement of supervisory attention system, what has been called "prepotent response", in this case either the alphabetical order or the repetition of the same letter.
A number of different brtain areas seem to be involved in this complex function, including dorsolateral prefrontal cortex, which might be specifically devoted to this kind of tasks
The task will be paced visual signals, displayed for about half a second in the central position of a laptop monitor. A microphone headset will be connected to the same laptop in order to record the vocal sequences, that will be later analysed through an adequate software.

SUBJECTIVE MEASURES
At the beginning of the experiment (i.e., in Day, about at 10 a.m.), participants will fill the abbreviated form of the Profile of Mood States (POMS-B; McNair, Lorr, & Droppleman, 1992) and the Trait subscale of the State-Trait Anxiety Inventory (STAI-Y; Spielberger, 1989).
The POMS-B is a shortened version of the original 65-item POMS, and it is a well established mood measure with satisfactory reliability and factorial validity (see also O’Connor, 2004). POM-B consists of 30 adjectives rated on a five-point scale designed to assess the following six mood states: tension, depression, anger, vigour, fatigue. Because of its relative brevity, the POMS-B is widely used in both clinical and experimental setting for assessing the fluctuation of mood states. The time reference for the test is adaptable for each setting where the POMS is administered. For this study, participants will be asked to respond based on their immediate feelings.
The trait scale of the well known STAI-Y consists of 20 item rated on a four-point scale, assessing relatively stable individual differences in anxiety proneness.
In addition, after each task session(i.e., 3 or 4, according to subgroup assign), the short version of the POMS Vigor (5 adjectives: lively, active, energetic, full of pep, and vigorous) and Fatigue (5 adjectives: worn out, fatigued, exhausted, sluggish, and wear) subscales will be administered in order assess variations in anxiety and in the feelings of having/not having the capacity to complete mental or physical activities.
Finally, before each task session (again, 3 or 4, according to subgroup assign) self-rated sleepiness will be measured by means of Stanford Sleepiness Scale (SSS), which is a seven-items scale with increasing score (e.g. Feeling active, vital, alert, or wide awake; 7: No longer fighting sleep, sleep onset soon; having dream-like thoughts).