How does reduction in pain lead to reduction in disability in patients with musculoskeletal pain?

Figures & data

Table 1 Sample characteristics (n=279)

Characteristic	Value
Age, Mean (SD), years	59.71 (13.79)
Sex, No (%)
Female	193 (69.7%)
Marital status, No (%)
Married	162 (58.9%)
Single	21 (7.6%)
Divorced/separated	38 (13.8%)
Living with a partner	24 (8.7%)
Widowed	30 (10.9%)
Educational level, No (%)
None	8 (3.0%)
Primary education	128 (47.9%)
Secondary education	91 (34.1%)
High school certificate	21 (7.9%)
University degree	19 (7.1%)
Pain history, Mean (SD), (years)	8.12 (8.31)
Number of hospital days, Mean (SD)	15.03 (4.49)

Abbreviations: M, mean; SD, standard deviation.

Figure 1 Model for the mediation analysis. The indirect effect is quantified by the product of paths a and b. The total effect (path c) is the sum of the indirect and direct (ć) effects.

Figure 2 CONSORT flow diagram – modified for non-randomized trial design.

Table 2 Repeated measures ANOVAs, Means±SDs, F-ratios, P-values, partial η² and effect sizes (Cohen’s d)

Variables	Pretreatment (T0)	Posttreatment (T1)	Follow-up (T2)	F (df)	P	η^2	ES (pre-post)	ES (pre-follow-up)	Bonferroni tests Mean difference
									T0–T1	T0–T2
Pain intensity	6.35±1.91	4.34±1.93	5.17±2.23	68.61 (2/290)	0.000	0.32	1.04	0.56	2.0***	1.18***
Disability	35.03±13.69	23.46±13.71	28.81±15.89	72.48 (2/288)	0.000	0.33	0.84	0.41	11.57***	6.22***
Depression	16.93±9.74	9.75±7.35	14.71±9.53	62.98 (2/264)	0.000	0.32	0.83	0.23	7.18***	2.22**
Acceptance	31.38±9.77	36.88±9.48	35.89±10.90	33.74 (2/284)	0.000	0.19	−0.57	−0.43	−5.49***	−4.51**
Catastrophizing	11.61±5.52	7.83±5.12	10.02±5.95	39.99 (2/294)	0.000	0.21	0.71	0.27	3.78***	1.58**

Note: ***P<0.001; **P<0.01.

Abbreviations: df, degrees of freedom; ES, effect size; NRS, Pain intensity was measured with the Numerical Rating Scale; PDI, disability with the Pain Disability Index; CES-D, depression with the German short version of the Center for Epidemiological Studies Depsression Scale; CPAQ, pain acceptance with the Chronic Pain Acceptance questionnaire; PCS (subscale “helplessness”), catastrophizing with the Pain Catastrophizing Scale.

Table 3 Results of univariate regression analyses on changes in psychological variables (depression, catastrophizing, acceptance)

Predictor	Criterion	R^2	B	SEB	β	P
Change in pain intensity (T0–T2)	Change in depression (T0–T2)	0.15	1.17	0.22	0.39	0.000
	Change in catastrophizing (T0–T2)	0.15	0.85	0.16	0.39	0.000
	Change in acceptance (T0–T2)	0.19	1.67	0.27	0.44	0.000

Table 4 Results of multiple mediation analyses: mediation of indirect effects of changes in pain intensity on changes in pain-related disability

Mediating variable (M)	Independent variable (X)	Dependent variable (Y)	Effect of X on M	Effect of M on Y	Partial effect of control variables on Y	Indirect effect	BCa, 95% CI^†
							Lower	Upper
Change in depression (T0–T2)	Change in pain intensity (T0–T2)	Change in disability (T0–T2)	0.45***	0.15*		0.06	0.01	0.14
Change in catastrophizing (T0–T2)			0.48***	0.14*		0.07	0.005	0.17
Change in pain acceptance (T0–T2)			−0.44***	−0.40***		0.17	0.10	0.28
Control variables
Age					0.008^ns
Sex					0.12^ns
Pain history					0.0006^ns

Notes: ^†Confidence intervals containing 0 are interpreted as ns; ***P<0.001; *P<0.05; ^ns Not significant.

Abbreviation: BCa, bias corrected and accelerated bootstrapping confidence intervals that include corrections for both median bias and skew.