Table 1. Sleep quality and legal drug consumption before, during and after an exam period.
| Pre-Baseline | ExamPeriod | Post-Baseline | Friedman’s Statistic | ||
| n | n = 139 | n = 122 | n = 117 | (df = 2, n = 106) | |
| Variable | Mean ± SD | X2 F, | Post-Hoc | ||
| Pittsburgh Sleep Quality Index (PSQI): | |||||
| Bedtime (Daytime ± h) | 23∶47±1.11 | 23∶50±1.32 | 00∶01±1.70 | – | – |
| Waketime (Daytime ± h) | 08∶06±1.25 | 07∶58±1.42 | 08∶40±2.66 | – | – |
| Time in Bed (h) | 8.31±0.96 | 8.14±1.11 | 8.65±1.22 | 12.54** | B** |
| Sleep Onset Latency (min) | 19.6±23.0 | 24.3±21.8 | 17.8±18.5 | 20.50*** | B** |
| % of Cases with Sleep Onset Latency ≥30 min | 22.3% | 34.4% | 18.8% | – | – |
| Reported Sleep Time (h) | 7.35±1.01 | 7.10±1.04 | 7.84±1.21 | 17.53*** | B** |
| Sleep Efficiency Sub-Scale | 0.42±0.68 | 0.57±0.96 | 0.37±0.85 | 5.42n.s | – |
| Sleep Efficiency in % | 88.7±0.1% | 87.9±0.1% | 90.6±0.1% | 13.99** | B*, C* |
| Subjective Sleep Quality | 0.43±0.68 | 0.57±0.96 | 0.37±0.85 | 40.75*** | A**, B*** |
| % of Cases with Very Good/Fairly Good/FairlyBad/Very Bad Sleep Quality | 27.3/61.2/10.1/1.4% | 7.4/66.4/23.0/3.3% | 31.6/62.4/5.1/0.9% | – | – |
| Hypnotics use: | 0.02±0.15 | 0.04±0.27 | 0.02±0.18 | – not enough cases | |
| Daytime Dysfunction/Sleepiness Score | 1.03±0.75 | 1.28±0.75 | 0.81±0.73 | 28.19 *** | B ***, C * |
| Sleep Disturbance Sub-Scale | 0.99±0.32 | 0.97±0.34 | 0.90±0.40 | 3.85 | – |
| PSQI Global Score | 4.95±2.53 | 6.25±2.82 | 4.10±2.39 | 47.43 *** | A ***, B ***, C * |
| % of Cases with PSQI >5 | 34.5% | 53.3% | 21.4% | – | – |
| Additional Sleep Scales: | |||||
| Regensburg Insomnia Scale (RIS) | 7.12±4.93 | 8.79±5.51 | 6.24±3.96 | 29.06*** | A**, B*** |
| Legal Drug Consumption and Current Health Status (Self-report): | |||||
| Caffeine (Cups) | 4.76±5.67 | 7.10±9.51 | 4.56±5.52 | 25.88 *** | A **, B ** |
| Nicotine (Cigarettes) | 7.24±25.54 | 7.19±29.12 | 5.39±20.75 | 0.45 n.s. | – |
| Alcohol (drinks) | 5.94±6.31 | 3.42±4.42 | 6.29±7.88 | 19.16 *** | A **, B * |
| % of Cases with Acute Infections, Injuries,or Exacerbations of Pre-Existing Conditions | 18.7 | 8.2 | 18.8 | – | – |
| Perceived Stress | |||||
| Perceived Stress Scale (PSQ-20) | 33.68±17.62 | 54.06±19.34 | 29.62±18.24 | 98.34*** | A***, B***, C* |
Higher PSQI scores denote lower sleep quality. Friedman’s test statistic (X2 F) was used to determine changes in PSQI and drug intake over time.
Abbreviations: Post-hoc differences are denoted as “A”: between Pre-Baseline and Exam Period, “B”: between Exam Period and Post-Baseline, and “C”: between Pre- and Post-Baseline. n.s.: not significant. * p<0.05, ** p<0.01, *** p<0.001.