Individual questions for component 5 (sleep disturbance) in the Pittsburgh Sleep Quality Index (PSQI) questionnaire
| Variable | Poor sleep quality (PSQI>5) | Good sleep quality (PSQI≤5) | p-value |
| Cannot get to sleep within 30 min | 2 (1–3) | 0 (0–1) | <0.0001 |
| Wake up in the middle of the night or early morning | 3 (2–3) | 2 (0–3) | 0.002 |
| Have to get up to use the bathroom | 3 (2–3) | 3 (2–3) | 0.45 |
| Cannot breathe comfortably | 2 (0–3) | 0 (0–2) | 0.02 |
| Cough or snore loudly | 3 (1–3) | 1 (0–3) | 0.07 |
| Feel too cold | 1 (0–3) | 1 (0–1.25) | 0.02 |
| Feel too hot | 1 (0–2.5) | 0 (0–0.25) | 0.0004 |
| Have bad dreams | 1 (0–3) | 0 (0–0) | 0.14 |
| Have pain | 1 (0–3) | 0 (0–2) | 0.006 |
| Other reasons | 1 (0–3) | 0 (0–1) | 0.001 |
Data presented as median (interquartile range), unless stated otherwise. Scores are as follows. 0: not during the past month; 1: less than once a week; 2: one or twice a week; 3: three or more times a week.