Table 3.
Factor Structure of the Iowa Sleep Disturbance Inventory (ISDI) Scales
| ISDI Scale | Scale Development Sample
|
Scale Validation Samples
|
||||||
|---|---|---|---|---|---|---|---|---|
| Student
|
Student
|
Psychiatric patient
|
Sleep disorder patient
|
|||||
| I | II | I | II | I | II | I | II | |
| Fragmented Sleep | .66 | −.03 | .65 | −.12 | .79 | −.06 | .75 | −.03 |
| Initial Insomnia | .65 | .04 | .64 | .08 | .72 | −.06 | .73 | .05 |
| Light Sleep | .59 | −.14 | .53 | −.23 | .57 | −.09 | .59 | −.13 |
| Anxiety at Night | .53 | .14 | .48 | .12 | .67 | .14 | .49 | .12 |
| Nightmares | .33 | .13 | .36 | .12 | .30 | .16 | .24 | .22 |
| Sensations at Night | .28 | .20 | .32 | .05 | .41 | .11 | .44 | .06 |
| Movement at Night | .15 | .07 | .18 | .05 | .26 | .25 | .31 | .28 |
| Fatigue | .09 | .73 | .21 | .65 | .04 | .80 | .08 | .84 |
| Excessive Sleep | −.18 | .62 | −.20 | .48 | −.14 | .56 | −.27 | .70 |
| Nonrestorative Sleep | .16 | .59 | .05 | .72 | .13 | .75 | .18 | .72 |
| Irregular Schedule | .13 | .39 | .02 | .54 | .30 | .25 | .29 | .35 |
Note. n = 335 (students, scale development), 374 (students, scale validation), 188 (psychiatric patients), 205 (sleep disorder patients). I = Insomnia, II = Lassitude. Factor loadings of |.30| and higher are highlighted.