Table 1.

Definitions or explanations of all sleep parameters used to describe sleep quality. Items in italic style represent sleep outcomes added during data analysis.

Sleep parameter	Definition/Explanation
Total sleep time (TST)	Total minutes of night-time sleep (“Time in bed” minus “wake after sleep onset” minus “sleep onset latency” OR “sleep duration” – “wake after sleep onset”)
Sleep duration	Total amount of time between sleep onset and offset (“time in bed” minus “sleep onset latency”)
Time in bed	Total number of minutes in bed during the night; The time between Bedtime and wake-up time.
Bedtime	Time of going to bed
Wake-up time	Time of waking
Wake after sleep onset (WASO)	Total number of minutes spent awake after sleep onset during the sleep period at night
Sleep efficiency (SE)	Number of minutes of actual sleep (TST) during the night divided by the number of minutes in bed, multiplied by 100
Sleep onset latency (SOL)	Duration between bedtime and sleep onset
Nighttime Awakenings	Total number of wake episodes between bedtime and wake time.
Total daily sleep time	Total minutes of sleep in a 24h period
Daytime Sleep time	Number of minutes sleep during daytime
Pittsburgh Sleep Quality Index (PSQI) [229]	19 self-rated questions (and 5 questions rated by the bed partner or roommate) which assesses sleep behavior from the previous month. PSQI has 7 subcategories, which sums up to a score between 0 and 21: subjective sleep quality, sleep latency, sleep duration, sleep efficiency, daytime dysfunctions, sleep disturbances, sleep medication). A total score ≥ 5 is considered poor quality.
Richards-Campbell Sleep Questionnaire (RCSQ) [244]	5 self-rated questions which assess sleep quality of the previous night, rated on a 100 mm Visual Analogue Scale (VAS). Questions are about awakenings, sleep quality, sleep latency, sleep depth, and returning to sleep. The average of all questions is considered the RCSQ total score. A total score ≤ 50 is considered poor sleep quality.
Verran Snyder-Halpern Sleep scale (VSH) [247]	Originally an 8-item VAS tool to capture sleep latency, fragmentation, length and depth, but often the extended 15-item version is used which sums scores to calculate sleep quality in three domains: sleep effectiveness (5 questions, sums up to scores between 0 and 500), sleep disturbance (7 questions, sums up to scores between 0 and 700) and supplemental sleep (4 questions, sums up to scores between 0 and 400). For disturbance and supplementation, higher scores indicate worse sleep quality, whereas for effectiveness, higher scores indicate better sleep quality.
Insomnia Severity Index (ISI) [248]	7 self-rated questions, using a 5-point Likert scale, to assess the severity of sleep-onset, sleep-maintenance, and early awakenings, as well as the satisfaction with current sleep patterns, interference with daytime functioning, noticeability of impairment to others and level of distress. Assesses the last 2 weeks. Total scores range from 0 to 28, with scores of 0–7, 8–14, 15–21 and 22–28 deemed indicative of no clinically significant insomnia, subthreshold insomnia, moderate insomnia and severe insomnia, respectively.
Epworth Sleepiness Scale (ESS) [249]	8 self-report items to evaluate the general sleepiness state within a day, using a 4-point Likert type scale. Total scores range from 0 to 24, where 0–5 indicates enough sleep, 6–10 indicates slight drowsiness, 11–15 indicates average drowsiness and >15 indicates severe drowsiness.
St. Mary Hospital Sleep Questionnaire [250]	11 self-reported items to assess sleep pattern disorders, using a 3-point Likert type scale. Total scores range from 11 to 44, where scores of 11–21 indicate slight sleep disorders, 22–32 indicate average disorders and 33–44 indicate severe sleep disorders.
PROMIS Sleep disturbance [251]	8- or 4-items questionnaire to assess sleep quality of the previous night, rated on a five-point scale. A standardized T-score can be calculated from the total score, to allow for comparison to a reference population. A patient with a T-score of 60 has a sleep quality that is worse than approximately 84% of persons in the reference population.
Karolinska Sleepiness scale [252]	Nine-point Likert scale assessing the patient's subjective sleepiness over the past 10 min, ranging from 1 = very alert to 9 = very sleepy.