CBT TAU
Figure 8. Change in Wake Time After Sleep Onset (Hours) from Baseline to Post-Treatment in CBT-I and Treatment as Usual (TAU) Groups (n=19; Outliers Adjusted)
Table 6.
Means (Standard Deviations) and Effect Sizes of Sleep-Related Variables in CBT-I and Treatment as Usual Groups (n=19; Outliers Adjusted)
Effect Size (d )
CBT TAU CBT TAU
Insomnia Severity Index (ISI) Score* 21.7 (3.8) 22.9 (3.2) 14.7 (8.5) 22.6 (3.1) 1.05 Sleep Onset Latency (SOL)* 1.1 (1.1) 0.9 (1.0) 0.6 (0.6) 0.9 (0.7) 0.80
Total Sleep Time (TST)* 5.7 (2.2) 6.3 (1.4) 6.5 (2.6) 5.2 (2.2) 0.89
Wake Time After Sleep Onset (WASO) 0.9 (0.5) 1.0 (0.4) 0.4 (0.4) 0.6 (0.4) 0.09 Sleep Efficiency (SE)* 58.0 (22.9) 73.4 (10.3) 79.1 (21.0) 66.8 (21.7) 1.37
Baseline M (SD) Post-Treatment M (SD)
* Indicates significant (p < .05) or marginally significant (p < .10) time by group interaction.
Change in Sleep Variables within the CBT-I Treatment Group with Crossover Participants. By combining the CBT-I group with those who crossed over to the CBT-I condition after completing the treatment as usual period, treatment effects are able to be more closely examined in a slightly larger sample. Doing so maximizes the ability of the analysis to detect clinically important change. Only those who completed the five-session treatment were included in this analysis (n=14). Results of paired samples t-tests showed a significant change
57
from baseline to posttreatment for ISI Score, t(13) = 3.43, p < .01; sleep efficiency, t(13) = -3.61, p < .01; sleep onset latency, t(13) = 3.25, p < .01; and wake time after sleep onset, t(13) = 2.30, p < .05. No significant differences between baseline and post-treatment data were found for total sleep time (p = .39). Figure 9 shows the improvement in sleep efficiency within individual cases across treatment.
20%
30%
40%
50%
60%
70%
80%
90%
100%
Baseline Post-Treatment
S le ep E ff ic ie n cy
Figure 9. Change in Sleep Efficiency within Individual Cases from Baseline to Post-Treatment in CBT-I Treatment Group with Crossovers (n=14; Outliers Adjusted)
Table 7. Sleep Diary Variable Means (Standard Deviations) and Significance Levels for Combined Crossovers and CBT-I Treatment Group at Baseline and Post-Treatment (n=14;
Outliers Adjusted)
Baseline Post-Treatment p -value Effect Size (d ) Insomnia Severity Index (ISI) Score* 21.8 (3.7) 14.9 (7.6) 0.004 1.00
Sleep Onset Latency (SOL)* 1.1 (1.1) 0.5 (0.6) 0.006 1.15
Total Sleep Time (TST) 5.4 (2.1) 5.9 (2.4) 0.39 0.24
Wake Time After Sleep Onset (WASO)* 0.8 (0.5) 0.4 (0.4) 0.039 0.62
Sleep Efficiency (SE)* 59.7 (22.0) 80.6 (19.1) 0.003 0.97
* Indicates significant change from baseline to post-treatment (p < .05).
58 Hypothesis 2
Change in Use of Sleep Medication by Group. To test the second hypothesis, that the CBT-I group would show reduced hypnotic use compared to the TAU group after treatment with CBT-I, repeated measures ANOVA was used. Prior to the analysis, assumptions of normality, linearity, and independence of observations were checked. Outliers were identified by
examining boxplots and creating standardized z-scores for the baseline and post-treatment variable of number of days of medication use per week. As a result of high skewness and kurtosis, outliers were adjusted by calculating z-scores for each data point and replacing all values with z-scores greater than 1.96 (p < .05) with the next closest value under the cut-off from the sample for that variable. Outliers were detected and changed for three data points for
baseline medication use (Z = -1.98; Z = -1.98; Z = -2.97) and three data point for post-treatment medication use (Z = -2.15; Z = -2.15; Z = -3.16). Sphericity was not violated, as confirmed by the results of Mauchly's test of sphericity (all Epsilons = 1). Results of the ANOVA showed no significant time by group interaction for use of sleep medication between baseline and post-treatment (p = .429).
Hypothesis 3
Change in Depression, Anxiety, and Health-Related Quality of Life by Group. To test the third hypothesis, that the CBT-I group would show reduced psychiatric symptoms (depression and anxiety) and improved health-related quality of life after treatment compared to the TAU group, repeated measures MANOVA and repeated measures ANOVA were used. Prior to the analyses, data were checked for statistical assumptions, including normality, linearity, and multicollinearity. After examining boxplots and creating standardized z-scores for all variables, no outliers were identified. Skewness and kurtosis values were within the acceptable range of -1
59
to 1. Prior to the MANOVA, scatterplots of the dependent variables were eyeballed for linearity and due to the linear relationship observed between the data points, this assumption was
determined to be met. Multicollinearity was examined prior to the analysis by running bivariate correlations between the variables. Correlations between the variables were significant and high enough to warrant them being used together in the MANOVA but not so high that the
assumption of multicollinearity was presumed to be violated (r < .8). After running the
MANOVA, the assumption of homogeneity of variance-covariance matrices was checked using Box’s M test of equality of covariance matrices. This test was nonsignificant (p = .550),
suggesting no violation of this assumption. To test for equality of error variances, Levene’s test was used. Results were nonsignificant (all ps > .05), suggesting no violation.
Results of the MANOVA showed no significant time by group interaction (p = .388).
See Figures 10 and 11 for changes in mean GAD-7 score and mean PHQ-9 score between the two groups across treatment.
12 12.5 13 13.5 14 14.5 15 15.5 16 16.5
Baseline Post-Treatment
G A D -7 Score
CBTTAU
Figure 10. Change in GAD-7 Score from Baseline to Post-Treatment in CBT-I and Treatment as Usual (TAU) Groups (n=19)
60 14
15 16 17 18 19 20
Baseline Post-Treatment
PH Q -9 Score
CBTTAU
Figure 11. Change in PHQ-9 Score from Baseline to Post-Treatment in CBT-I and Treatment as Usual (TAU) Groups (n=19)
Prior to the ANOVAs with SF-36 component scores as DVs, the assumption of independence of observations was confirmed to be met. Sphericity was not violated in either ANOVA, as confirmed by the results of Mauchly's test of sphericity (all Epilons = 1). Results of the first ANOVA, which included the SF-36 physical component score as the DV, showed no significant time by group interaction (p = .425). Similarly, no significant time by group interaction was found for the second ANOVA, which included the SF-36 mental component score as the DV, (p = .263). See Figures 12 and 13 for changes in mean SF-36 physical component score and mean SF-36 mental component score between the two groups across treatment.
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Figure 12. Change in SF-36 Physical Component Score from Baseline to Post-Treatment in CBT-I and Treatment as Usual (TAU) Groups (Higher Scores Reflect Higher Ratings of Quality of Life; n=19)
Figure 13. Change in SF-36 Mental Component Score from Baseline to Post-Treatment in CBT-I and Treatment as Usual (TAU) Groups (Higher Scores Reflect Higher Ratings of Quality of Life;
n=19)