Effect of mindfulness-based stress reduction on sleep quality: Results of a randomized trial among Danish breast cancer patients

Figures & data

Figure 1. Numbers of study participants during the study period. ITT, intention-to-treat.

Table I. Baseline characteristics of participants in the randomized controlled trial.

Characteristic	MBSR n = 168	Controls n = 168	p-value*
Age at operation [mean, years (SD)]	53.9 (10.1)	54.4 (10.5)	0.66
Time since diagnosis [mean, months (SD)]	7.5 (5.0)	7.9 (5.1)	0.49
Breast cancer stage [n (%)]
I	51 (30.4)	64 (38.1)
II	109 (64.9)	101 (60.1)	0.06
III	8 (4.8)	3 (1.8)
Treatment [n (%)]
Allocated to chemotherapy
Yes	78 (46.4)	82 (48.8)
No	65 (38.7)	67 (39.9)	0.93
Unknown	25 (14.9)	19 (11.3)
Allocated to radiotherapy
Yes	125 (74.4)	145 (86.3)
No	37 (22.0)	21 (12.5)	0.5
Unknown	6 (3.6)	2 (1.2)
Allocated to hormonal therapy
Yes	91 (54.2)	88 (52.4)
No	50 (29.8)	60 (35.7)	0.38
Unknown	27 (16.1)	20 (11.9)
Charlson comorbidity index at date of diagnosis [n (%)]
0	146 (86.9)	145 (86.3)
1	18 (10.7)	18 (10.7)	0.83
≥ 2	4 (2.4)	5 (3.0)
Married [n (%)]	123 (73.2)	120 (71.4)	0.72
Further and higher education [n (%)]	131 (78.0)	128 (76.2)	0.84
Hot flush score [mean (SD)]	6.10 (12.65)	6.95 (11.98)	0.53
Psychological distress [mean (SD)]	0.59 (0.43)	0.58 (0.37)	0.72

*MBSR group compared with control group by t-test.

Table II. Differences in sleep scale scores between MBSR and control group.

	Baseline Mean (n)			Post-intervention Mean (n)			6-month follow-up Mean (n)			12-month follow-up Mean (n)			ITT analyses
	MBSR	Control	^#p	MBSR	Control	^#p	MBSR	Control	^#p	MBSR	Control	^#p	^§p	^§p, LOCF
Sleep disturbance	30.15 (168)	32.17 (166)	NS	24.91 (134)	30.40 (144)	0.03*	25.38 (122)	28.37 (143)	NS	25.80 (121)	27.74 (143)	NS	0.21	0.21
Snoring	15.13 (115)	18.57 (98)	NS	17.62 (84)	24.47 (85)	NS	15.68 (74)	23.45 (87)	0.06	14.17 (79)	24.44 (90)	0.01*	0.71	0.95
Shortness of breath or headache	10.00 (168)	11.76 (165)	NS	10.00 (134)	8.85 (144)	NS	9.51 (122)	11.05 (143)	NS	9.26 (121)	10.78 (141)	NS	0.41	0.47
Sleep adequacy	55.77 (168)	53.73 (166)	NS	59.70 (134)	53.68 (144)	0.06	58.52 (122)	54.97 (143)	NS	58.10 (121)	54.32 (141)	NS	0.37	0.39
Somnolence	30.60 (168)	29.72 (166)	NS	24.73 (134)	26.44 (144)	NS	23.33 (122)	27.09 (143)	0.09	24.44 (121)	26.34 (141)	NS	0.79	0.73
Sleep problem index I	29.78 (168)	31.73 (166)	NS	25.39 (134)	29.79 (144)	0.03*	26.56 (122)	29.39 (143)	NS	26.97 (121)	29.39 (141)	NS	0.61	0.62
Sleep problem index II	30.70 (168)	32.02 (166)	NS	26.04 (134)	30.46 (144)	0.03*	26.52 (122)	29.61 (143)	NS	26.84 (121)	29.29 (143)	NS	0.33	0.32
Sleep quantity (hours of sleep)	7.10 (165)	7.02 (154)	NS	7.08 (124)	6.88 (134)	NS	7.01 (108)	7.01 (131)	NS	7.08 (112)	7.07 (137)	NS	0.49	0.63
Optimal sleep (7–8 hours)	0.64 (165)	0.58 (154)	NS	0.73 (124)	0.63 (134)	NS	0.68 (108)	0.65 (131)	NS	0.72 (112)	0.65 (137)	NS	0.15	0.11

LOCF, last observation carried forward; MBSR, mindfulness-based stress reduction; NS, not significant; ITT, intention-to-treat.

p-values of 0.10 or lower are shown for comparison of mean scores at each time.

^#t-test; ^§Analysis based on mixed effect linear models, and baseline sleep score included as covariate.

Table III. Differences in change scores between MBSR and control group at different times.

	Change from baseline to post-intervention Mean change (n)				Change from baseline to 6-month follow-up Mean change (n)				Change from baseline to 12-month follow-up Mean change (n)
	MBSR	Control	p	Effect size	MSBR	Control	p	Effect size	MBSR	Control	p	Effect size
Sleep disturbance	−4.58 (134)	−1.53 (142)	NS	0.16	−4.10 (122)	−3.46 (141)	NS	0.04	−3.81 (121)	−5.35 (141)	NS	−0.09
Snoring	4.11 (73)	6.94 (72)	NS	0.14	0.90 (67)	3.47 (75)	NS	0.12	0.58 (69)	6.67 (72)	0.1	0.28
Shortness of breath or headache	−1.49 (134)	0.28 (141)	NS	0.1	−1.15 (122)	1.86 (140)	NS	0.16	−0.66 (121)	1.16 (138)	NS	0.1
Sleep adequacy	3.13 (134)	−1.34 (142)	NS	−0.18	3.11 (122)	0.28 (141)	NS	−0.12	2.48 (121)	−0.72 (139)	NS	−0.13
Somnolence	−5.82 (134)	−2.72 (142)	NS	0.18	−7.98 (122)	−2.79 (141)	0.02*	0.29	−6.69 (121)	−2.73 (139)	0.09	0.21
Sleep problem index I	−3.92 (134)	−1.08 (142)	NS	0.19	−3.36 (122)	−1.58 (141)	NS	0.12	−2.70 (121)	−1.68 (139)	NS	0.07
Sleep problem index II	−4.24 (134)	−0.79 (142)	0.05*	0.24	−4.26 (122)	−1.80 (141)	NS	0.17	−3.72 (121)	−2.52 (141)	NS	0.08
Sleep quantity (hours of sleep)	−0.02 (123)	−0.16 (122)	NS	−0.13	−0.17 (107)	−0.05 (120)	NS	0.11	−0.05 (111)	0.06 (126)	NS	0.08
Optimal sleep (7–8 hours)	0.06 (123)	0.07 (122)	NS	0.02	0.00 (107)	0.08 (120)	NS	0.16	0.04 (111)	0.07 (126)	NS	0.07

MBSR, mindfulness-based stress reduction; NS, not significant.

A positive change score indicates an increase in the sleep scale score between baseline and follow-up, and a negative change score indicates a decrease in the sleep scale score. For sleep adequacy, a positive change score reflects improved sleep quality. For all other subscales and indexes, a negative change score reflects improved sleep quality. p-values of 0.10 or lower are shown.

*Statistically significant at p < 0.05; ^#t-test.

Figure 2. Change in sleep problem index II between baseline and post-intervention. Estimated quantile regression coefficients and 95% confidence intervals (grey areas) for changes in sleep problem index II between baseline and post-intervention. The table shows the estimated quantile regression coefficients for the 25th, 50th and 75th quantile. The values shown for the study group are for cases, as the controls were used as reference.

Figure 3. Quantile regression fit plot for change in sleep problem index II between baseline and post-intervention. The slopes of the lines are defined by the estimated quantile regression coefficient for baseline score. The estimated quantile regression coefficients of the study group determine the vertical difference between the lines representing cases and controls at a given percentile.