Table 2.
Characteristics of participants (mean ± standard deviation) within subsamples according to questionnaires completed.
| CPG + 4-DSQ (N = 1,862) | CPG only (N = 1,011) | 4-DSQ only (N = 635) | |
|---|---|---|---|
| Age (y) | 50.83 ± 14.46 | 48.81 ± 16.67* | 49.96 ± 14.97 |
| Sex (female/male) | 1459/403 | 782/229 | 443/192*** |
| ISI | 10.17 ± 7.10 | 10.36 ± 7.16 | 9.61 ± 7.41* |
| 4-DSQ | |||
| Distress | 10.34 ± 8.06 | – | 9.33 ± 8.23*** |
| Somatization | 7.59 ± 5.59 | – | 5.72 ± 5.49*** |
| Anxiety | 2.35 ± 3.72 | – | 1.95 ± 3.44** |
| Depression | 1.53 ± 2.87 | – | 1.43 ± 2.73 |
| CPG pain intensity | 40.81 ± 19.86 | 39.70 ± 20.47 | – |
| Perceived sleep–pain relationship | |||
| Pain after worse sleepa | 0.52 ± 0.82 | 0.51 ± 0.82 | – |
| Pain after better sleepa | −0.38 ± 0.75 | −0.40 ± 0.76 | – |
| Sleep after more painb | −0.50 ± 0.97 | −0.49 ± 0.97 | – |
| Sleep after less painb | 0.19 ± 0.64 | 0.18 ± 0.62 | – |
4-DSQ, Four-Dimensional Symptom Questionnaire; CPG, Chronic Pain Grade; ISI, Insomnia Severity Index.
Significance of difference from the “CPG + 4-DSQ” subsample (*p < 0.05, **p < 0.01, ***p < 0.001) as determined by Fisher exact test for sex and by Wilcoxon rank-sum tests for the other variables.
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).
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).