Table 1.
Characteristics of participants (mean ± standard deviation).
| Age (y) | 50.09 ± 15.24 |
| Sex (female/male) | 2684/824 |
| ISI | 10.12 ± 7.17 |
| 4-DSQ (N = 2,497) | |
| Distress | 10.08 ± 8.12 |
| Somatization | 7.11 ± 5.62 |
| Anxiety | 2.25 ± 3.65 |
| Depression | 1.50 ± 2.84 |
| CPG pain intensity (N = 2,873) | 40.42 ± 20.08 |
| Perceived sleep–pain relationship (N = 2,873) | |
| Pain after worse sleepa | 0.52 ± 0.82 |
| Pain after better sleepa | −0.38 ± 0.76 |
| Sleep after more painb | −0.50 ± 0.97 |
| Sleep after less painb | 0.18 ± 0.63 |
4-DSQ, Four-Dimensional Symptom Questionnaire; CPG, Chronic Pain Grade; ISI, Insomnia Severity Index.
a
Responses to the items “If I sleep worse/better than usual on one night, the next day the chance of feeling pain is …” with ratings ranging from −3 (much smaller) to 3 (much bigger).
b
Responses to the items “If I have a day with more/less pain than usual, the following night I usually sleep …” with ratings ranging from −3 (much worse) to 3 (much better).