Table 5.
Sleep characteristics by nightmare status on the Nightmare Disorder Index
| Total subsample (N = 400) | No nightmares (N = 190) | Subthreshold nightmare symptoms (N = 178) | Probable nightmare disorder (N = 32) | ||||
|---|---|---|---|---|---|---|---|
| M (SD) | M (SD) | M (SD) | M (SD) | F | p* | Part. η2 | |
| Questionnaires | |||||||
| Sleep Quality (PSQI)+ | 5.27 (2.38) | 4.71 (2.11)a | 5.54 (2.42)b | 7.33 (2.57)c | 17.68 | <0.001 | 0.085 |
| Insomnia Symptoms (ISI)+ | 5.77 (4.5) | 4.65 (3.99)a | 6.40 (4.62)b | 9.00 (4.67)c | 15.96 | <0.001 | 0.076 |
| Sleep Diary | |||||||
| SOL (min) | 17.98 (15.36) | 17.47 (16.21) | 17.91 (14.58) | 21.43 (14.41) | 0.91 | 1.0 | 0.005 |
| NWAK (num) | 1.70 (1.00) | 1.46 (0.90)a | 1.86 (1.04)b | 2.28 (1.03)b | 13.76 | <0.001 | 0.065 |
| WASO (min) | 11.28 (11.25) | 10.60 (11.24) | 11.32 (10.99) | 15.05 (12.37) | 2.15 | 1.0 | 0.011 |
| TWAK (min) | 13.31 (10.88) | 13.26 (11.83) | 13.15 (10.05) | 14.44 (9.64) | 0.19 | 1.0 | 0.001 |
| TST (min) | 431.95 (49.86) | 429.07 (47.95) | 437.51 (50.70) | 418.07 (53.54) | 2.69 | 0.690 | 0.013 |
| SE (%) | 90.96 (5.16) | 91.10 (5.27) | 91.19 (4.92) | 88.83 (5.53) | 2.99 | 0.676 | 0.015 |
| SM (time) | 4.19 (2.66) | 4.18 (2.58) | 4.06 (2.67) | 5.00 (3.04) | 1.66 | 1.0 | 0.008 |
| Quality (0–4) | 2.57 (0.56) | 2.68 (0.57)a | 2.50 (0.54)b | 2.30 (0.47)b | 8.73 | <0.001 | 0.042 |
| Nightmare Frequency (sum) | 1.36 (2.25) | 0.67 (0.09)a | 1.75 (0.19)b | 3.31 (0.61)c | 26.68 | <0.001 | 0.118 |
| Nightmare Severity | 1.31 (0.70) | 1.12 (0.09)a | 1.43 (0.07)b | 1.37 (0.09) | 4.34 | 0.014 | 0.043 |
| Actigraphy | |||||||
| SOL+ (min) | 12.72 (10.71) | 12.45 (10.39) | 13.13 (11.33) | 12.09 (9.04) | 0.24 | 1.0 | 0.001 |
| NWAK+ (num) | 30.48 (8.49) | 29.72 (8.30) | 31.59 (8.57) | 28.76 (8.66) | 2.93 | 0.676 | 0.015 |
| WASO+ (min) | 33.30 (13.58) | 31.61 (12.73) | 34.73 (13.73) | 35.41 (16.74) | 2.83 | 0.676 | 0.014 |
| TWAK+ (min) | 13.70 (8.70) | 13.66 (9.45) | 13.71 (8.14) | 13.79 (7.18) | 0.00 | 1.0 | 0.000 |
| TST+ (min) | 402.01 (50.89) | 398.13 (51.91) | 407.04 (49.52) | 396.76 (51.40) | 1.58 | 1.0 | 0.008 |
| SE+ (%) | 86.95 (4.88) | 87.15 (5.08) | 86.84 (4.66) | 86.38 (4.99) | .412 | 1.0 | 0.002 |
| SM+ (time) | 4.24 (2.72) | 4.15 (2.53) | 4.18 (2.79) | 5.14 (3.27) | 1.85 | 1.0 | 0.009 |
Note. PSQI, Pittsburgh Sleep Quality Index; ISI, Insomnia Severity Index; SOL, sleep onset latency; NWAK, number of awakenings; WASO, wake after sleep onset; TWAK, terminal wakefulness; TST, total sleep time; SE, sleep efficiency; SM, sleep midpoint.
+For these measures, ns range from 387 to 396 due to missing data.
abcNonmatching letter pairs indicate significant difference for Tukey post-hoc comparisons across rows.
*p-values adjusted for multiple comparisons using Holm–Bonferroni correction.