Table 3.

Effects of a self-help book for insomnia compared to sleep hygiene advice among patients with obstructive sleep apnea and comorbid chronic insomnia concurrently being treated with continuous positive airway pressure (CPAP).

	Sleep hygiene advice (n = 83)			Self-help book (n = 81)
	Mean (SD) Pre – Post	t (df), p-valuea	Effect sizeb	Mean (SD) Pre – Post	t (df), p-valuea	Effect sizeb	F (df), p-valuesc
Intention-to-treat
BIS	26.8 (7.8) – 21.8 (10.1)	4.63 (80), <0.001	0.55	26.3 (6.4) – 22.4 (8.5)	4.78 (71), <0.001	0.52	0.57 (1,151), 0.45
ISI	17.0 (4.0) – 14.1 (5.8)	5.02 (73), <0.001	0.58	16.6 (4.4) – 13.6 (5.5)	6.33 (77), <0.001	0.60	0.04 (1,150), 0.84
AHId	24.9 (18.1) – 7.9 (14.6)	9.41 (82), <0.001	1.03	25.6 (19.9) – 8.7 (16.4)	8.23 (80), <0.001	0.93	0.01 (1,162), 0.94
No intention-to-treate
BIS	27.1 (7.6) – 19.9 (10.3)	4.93 (55), <0.001	0.80	25.2 (6.1) – 18.5 (7.7)	5.27 (41), <0.001	0.96	0.05 (1,96), 0.82
ISI	17.2 (3.7) – 13.1 (5.9)	5.38 (52), <0.001	0.83	16.2 (4.4) – 11.7 (5.0)	7.27 (52), <0.001	0.96	0.21 (1,104), 0.65
AHId	24.2 (16.9) – 3.1 (5.0)	10.91 (66), <0.001	1.69	24.6 (18.8) – 1.9 (1.8)	9.79 (59), <0.001	1.70	0.30 (1,125), 0.59

^aPaired t-test, comparing values before and after the intervention (separate tests for the self-help book and the sleep hygiene advice). ^bEffect size (Cohen’s d) for paired values. ^cGeneral Linear Model with repeated measures (a mixed between-within subjects 2 × 2 ANOVA) comparing the effect of the self-help book and the sleep hygiene advice. ^dAHI post-treatment was measured with data from the CPAP device. ^eIn these analyses the total number of patients varied between 98 (BIS), 106 ISI and 127 (AHI). BIS, Bergen Insomnia Scale; ISI, Insomnia Severity Index; AHI, apnea-hypopnea-index.