Table 4: Results of the mediation analyses.
Path coefficients, standard error, confidence intervals for each path of the model. Effect size is presented for the indirect effects. Each of the paths are represented in Figure 1. Mediation can be assumed when the indirect effect is significant, represented by CI that do not cross zero.
| Model | Path coefficienta | SE | t Test statistic | 95% CI | |
|---|---|---|---|---|---|
| Lower | Upper | ||||
| Model 1: SLP-COG & Insomnia | |||||
| Direct effect: Ethnicity -> SLP-COG (a1) | .08 | .33 | .24 | −.57 | .73 |
| Direct effect: Ethnicity -> insomnia (a2) | −.55 | .83 | −.67 | −2.18 | 1.08 |
| Direct effect: SLP-COG ->Pain (b1) | −.18 | .09 | −2.08* | −.35 | −.01 |
| Direct effect: insomnia ->Pain (b2) | .17 | .03 | 5.69** | .11 | .23 |
| Direct effect: SLP-COG ->insomnia (d21) | 1.33 | .21 | 6.41** | .92 | 1.75 |
| Direct effect: Ethnicity ->Pain (c’) | −.92 | .30 | −3.07* | −1.51 | −.33 |
| Indirect effect: Ethnicity->SLP-COG->Pain (a1b1) | [−.01] | .07 | −.19 | .12 | |
| Indirect effect: Ethnicity->Insomnia->Pain (a2b2) | [−.09] | .15 | −.46 | .20 | |
| Indirect effect: Ethnicity->SLP-COG->Insomnia ->Pain (a2 d21 b2) | [.02] | .09 | −.16 | .19 | |
| Model 2: PCS & Insomnia | |||||
| Direct effect: Ethnicity -> PCS (a1) | −4.78 | 1.82 | −2.63** | −8.37 | −1.18 |
| Direct effect: Ethnicity -> insomnia (a2) | −.28 | .94 | −.30 | −2.14 | 1.58 |
| Direct effect: PCS ->Pain (b1) | .06 | .01 | 4.76** | .04 | .08 |
| Direct effect: insomnia ->Pain (b2) | .12 | .02 | 5.01** | .08 | .17 |
| Direct effect: PCS ->insomnia (d21) | .05 | .04 | 1.29 | −.03 | .13 |
| Direct effect: Ethnicity ->Pain (c’) | −.64 | .28 | −2.26* | −1.21 | −.08 |
| Indirect effect: Ethnicity->PCS->Pain (a1b1) | [−.28]* | .14 | −.65 | −.05 | |
| Indirect effect: Ethnicity->Insomnia->Pain (a2b2) | [−.03] | .13 | −.34 | .18 | |
| Indirect effect: Ethnicity->PCS->Insomnia->Pain (a2 d21 b2) | [−.03] | .03 | −.14 | .01 | |
| Model 3: PCS-R & Insomnia | |||||
| Direct effect: Ethnicity -> PCS-R (a1) | −1.74 | .74 | −2.34* | −3.21 | −.27 |
| Direct effect: Ethnicity -> insomnia (a2) | −.41 | .94 | −.43 | −2.26 | 1.45 |
| Direct effect: PCS-R ->Pain (b1) | .12 | .03 | 3.75** | .06 | .18 |
| Direct effect: insomnia ->Pain (b2) | .13 | .03 | 5.17** | .08 | .18 |
| Direct effect: PCS-R ->insomnia (d21) | .07 | .10 | .72 | −.12 | .27 |
| Direct effect: Ethnicity ->Pain (c’) | −.72 | .29 | −2.48* | −1.29 | −.15 |
| Indirect effect: Ethnicity->PCS-R->Pain (a1b1) | [−.21]* | .10 | −.45 | −.05 | |
| Indirect effect: Ethnicity->Insomnia->Pain (a2b2) | [−.03] | .09 | −.22 | .11 | |
| Indirect effect: Ethnicity->PCS-R->Insomnia->Pain (a2 d21 b2) | [−.01] | .02 | −.06 | .01 | |
| Model 4: PCS-M & Insomnia | |||||
| Direct effect: Ethnicity -> PCS-M (a1) | −1.33 | .59 | −2.27* | −2.49 | −.17 |
| Direct effect: Ethnicity -> insomnia (a2) | −.55 | .94 | −.59 | −2.41 | 1.31 |
| Direct effect: PCS-M ->Pain (b1) | .13 | .04 | 3.14** | .05 | .21 |
| Direct effect: insomnia ->Pain (b2) | .14 | .03 | 5.36** | .09 | .19 |
| Direct effect: PCS-M ->insomnia (d21) | −.01 | .13 | −.11 | −27 | .24 |
| Direct effect: Ethnicity ->Pain (c’) | −.75 | .29 | −2.56* | −1.33 | −.17 |
| Indirect effect: Ethnicity->PCS-M->Pain (a1b1) | [−.17*] | .10 | −.44 | −.02 | |
| Indirect effect: Ethnicity->Insomnia->Pain (a2b2) | [−.08] | .14 | −.37 | .15 | |
| Indirect effect: Ethnicity->PCS-M->Insomnia ->Pain (a2 d21 b2) | [.01] | .03 | −.06 | .06 | |
| Model 5: PCS-H & Insomnia | |||||
| Direct effect: Ethnicity -> PCS-H (a1) | −1.70 | .86 | −1.97* | −3.41 | .01 |
| Direct effect: Ethnicity -> insomnia (a2) | −.21 | .92 | −.23 | −2.04 | 1.61 |
| Direct effect: PCS-H ->Pain (b1) | .12 | .03 | 4.46** | .07 | .17 |
| Direct effect: insomnia ->Pain (b2) | .12 | .03 | 4.62** | .07 | .17 |
| Direct effect: PCS-H ->insomnia (d21) | .19 | .08 | 2.20* | .02 | .36 |
| Direct effect: Ethnicity ->Pain (c’) | −.73 | .28 | −2.57* | −1.29 | −.17 |
| Indirect effect: Ethnicity->PCS-H->Pain (a1b1) | [−.21]* | .13 | −.53 | −.01 | |
| Indirect effect: Ethnicity->Insomnia->Pain (a2b2) | [−.03] | .12 | −.56 | .12 | |
| Indirect effect: Ethnicity->PCS-H->Insomnia->Pain (a2 d21 b2) | [−.04]* | .03 | −.14 | −.01 | |
SE – Standard error; CI – Confidence interval; IV – Independent variable; SLP-COG = Negative sleep cognitions; PCS – Pain Catastrophizing Scale
a
For the indirect effect this represents effect size in brackets [] and not a path coefficient
*
p < .05
**
p < .001.