Shift-work Disorder
Conditions
Brief summary
The goal is to investigate if the morningness-eveningness dimension mediates sleep and function on spilt night shifts (midnight-4am and 4am-8am). Does those with high score of morningness function relatively better on the last compared to the first split shift? Participants will: Record their sleep from 2 days prior to 2 days following the split shift During the shifts complete questionnaires assessing mood, sleepiness and perceived performance as well as complete cognitive tests: Psychomotor vigilance test, digit symbol substitution test, working memory scanning test, reversal learning test, and visual search test
Detailed description
A sample of 28 students will be recruited and exposed to two conditions in a randomized, controlled, crossover study. They will be assessed with subjective (sleep diary) and objective sleep measures (sleep radar) for 2 days before the night shift, during the night shift and 2 days following the night shift. The simulated night shifts will last from midnight to 8am and will be divided into two halves (midnight-4am and 4am-8am), denoted as split-shift, and for each participant separated by at least 1 week. Based on the Horne-Östberg Morningness-Eveningness Questionnaire (median spilt) two groups are created, from which participants will be randomized to the two orders of the spilt-shift. Each hour on each shift the participants will complete: Positive and Negative Affect Schedule (PANAS), Karolinska Sleepiness Scale, perceived performance and the following cognitive tests: Psychomotor vigilance test, Digit symbol substitution test, Working memory scanning test, Reversal learning test, and Visual search test. Data will be analyzed with linear mixed models with three fixed factors: Group (low vs. high morningness), shift (midnight-4am vs. 4am-8am), and hour and one random factor (participant).
Interventions
BEHAVIORALTime of night shift
Early vs. late night split night shift
Sponsors
University of Bergen
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
NONE
Masking description
Randomly allocated to order of night shifts (midnight-4am vs.4am-8am)
Intervention model description
A 2 (midnight-4am vs.4am-8am) within factor x 2 (below vs. above median on morningness) between factor experimental design
Eligibility
Sex/Gender
ALL
Age
18 Years to 40 Years
Healthy volunteers
Yes
Inclusion criteria
* 18-40 years old * no incorrectable vision problems
Exclusion criteria
\* regular use of sleep medication
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Total sleep time | Total sleep time between 6pm day before shift start to 6pm the day the shift end for both early night shift (midnight-04am) and late night shift (04am-08am) | Total sleep (sleep diary and radar). Higher values indicates more sleep |
| Psychomotor Vigilance Test (PVT) | Hourly during shifts (0:15am, 1:15am, 2:15am and 3:15am on early night shift; 4:15am, 5:15am, 6:15am and 7:15 am on late night shift) | Reaction time (mean 1/RT) and number of lapses (RTs≥500 ms). For mean 1/RT higher values are associated with best performance, on lapses higher values are associated with worst performance |
| Karolinska Sleepiness Scale (KSS) | Hourly during shifts (0:15am, 1:15am, 2:15am and 3:15am on early night shift; 4:15am, 5:15am, 6:15am and 7:15 am on late night shift) | Assessment of state sleepiness, range 1-9 (higher scores indicate worse state) |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Sleep efficiency (percentage of time in bed one sleeps) | Between 6pm day before shift start to 6pm the day the shift end for both early night shift (midnight-04am) and late night shift (04am-08am) | Sleep efficiency (diary and radar). Range from 0-100%. Higher scores indicate best state |
| Positive and Negative Affect Schedule (PANAS) | Hourly during shifts (0:15am, 1:15am, 2:15am and 3:15am on early night shift; 4:15am, 5:15am, 6:15am and 7:15 am on late night shift) | Assessment of mood/affect. Range 10-50. On positive mood subscale higher scores indicate best state, on negative mood state, higher scores indicate worst state |
| Self-rated performance | Hourly during shifts (0:15am, 1:15am, 2:15am and 3:15am on early night shift; 4:15am, 5:15am, 6:15am and 7:15 am on late night shift) | Self-rated performance on cognitive tests. Range 1-10. Higher scores indicate best performance rating |
| Digital Symbol Substitution Test | Hourly during shifts (0:15am, 1:15am, 2:15am and 3:15am on early night shift; 4:15am, 5:15am, 6:15am and 7:15 am on late night shift) | Test where one match symbols to numbers as fast as possible. Range 0-100. Higher scores indicate best performance |
| Working Memory Scanning Test (probed recall) | Hourly during shifts (0:15am, 1:15am, 2:15am and 3:15am on early night shift; 4:15am, 5:15am, 6:15am and 7:15 am on late night shift) | Test presenting list of words. Then words are presented and subjects decide if word was present or not in list presented. The accuracy and RTs for positive trials (where probe was present in list) will be used as dependent variables. Higher accuracy and lower reaction time are associated with best performance |
| Reversal Learning Test | Hourly during shifts (0:15am, 1:15am, 2:15am and 3:15am on early night shift; 4:15am, 5:15am, 6:15am and 7:15 am on late night shift) | Test measuring the ability to differentiating between go-stimuli and no-go stimuli before and after reversal of go and no-go stimuli. Discriminability (hit rate/false alarm rate) and response bias before and after reversal are recorded. Higher discriminability indicates better performance, higher response bias indicate worse performance |
| Visual Search Test | Hourly during shifts (0:15am, 1:15am, 2:15am and 3:15am on early night shift; 4:15am, 5:15am, 6:15am and 7:15 am on late night shift) | Multiple objects are presented, and from among them a target is identified. The task of the subject is finding the target. Outcomes are reaction time (RT) and accuracy. Lower reaction times and higher accuracy are associated with best performance |
Countries
Norway
Outcome results
None listed