Spreading of Pain in Patients with Chronic Pain is Related to Pain Duration and Clinical Presentation and Weakly Associated with Outcomes of Interdisciplinary Pain Rehabilitation: A Cohort Study from the Swedish Quality Registry for Pain Rehabilitation (SQRP)

Figures & data

Table 1 Gender, Born Outside Europe, University Education and High Health-care Seeking by Pain Spreading in Four Categories. Furthest to the Right is Shown Statistics (Chi-squared Test)

Variable	1–6 Regions	7–12 Regions	13–18 Regions	19–36 Regions	Statistics
Gender (male, %)	43.7	34.1	24.2	13.8	χ^2=2440.19, df=3, p<0.001
Born outside Europe (%)	11.5	12.7	14.0	16.9	χ^2=137.88, df= 3, p<0.001
University education (%)	25.7	26.1	23.8	20.7	χ^2=107.33, df= 3, p<0.001
High health-care seeking (≥4 times/year; %)	66.7	69.4	71.4	74.3	χ^2=156.71, df=6, p<0.001

Abbreviation: df, degrees of freedom.

Table 2 Age, Duration of Period Without Work/Studies, Pain Duration and the 22 Mandatory Outcome Variables at Baseline (Mean, SD and n) by the Four Pain Categories Based on Pain Spreading. Group Comparison (ANOVA, p-value) and Effect Size (Hedges’ g) for the Pairwise Comparison 1–6 Regions vs 19–36 Regions are to the Far Right

Category	1–6	Regions		7–12	Regions		13–18	Regions			19–36	Regions		Statistics
Variables	N	Mean	SD	N	Mean	SD	N	Mean	SD		N	Mean	SD	p-value	ES
Age (years)	8008	42.81	12.48	10,438	42.83	11.68	8554	43.50	11.02		11,884	43.26	10.55	<0.001	0.04
Days no work/studies	2636	1153	2572	3789	1168	2207	3385	1349	2296		5360	1570	2485	<0.001	0.17
Pain duration (days)	7339	2173	2963	9520	2637	3049	7628	3352	3332		10,407	3994	3513	<0.001	0.55^b
NRS-7days	7824	6.50	1.96	10,273	6.81	1.76	8426	7.10	1.64		11,739	7.55	1.57	<0.001	0.60^b
HAD-A	7882	7.74	4.75	10,274	8.77	4.77	8425	9.35	4.91		11,723	10.51	5.12	<0.001	0.56^b
HAD-D	7891	7.39	4.63	10,282	8.29	4.58	8432	8.90	4.61		11,720	9.79	4.71	<0.001	0.51^b
MPI-pain-sever	7882	4.18	1.08	10,274	4.35	0.94	8428	4.52	0.86		11,708	4.78	0.82	<0.001	0.64^b
MPI-pain interfer	7801	4.09	1.21	10,172	4.31	1.08	8363	4.47	1.01		11,596	4.71	0.94	<0.001	0.59^b
MPI-control	7846	2.96	1.18	10,237	2.77	1.14	8401	2.62	1.13		11,654	2.34	1.16	<0.001	0.53^b
MPI-distress	7849	3.17	1.37	10,253	3.41	1.30	8399	3.54	1.30		11,668	3.78	1.31	<0.001	0.46^a
MPI-socsupp	7829	4.28	1.37	10,217	4.19	1.37	8370	4.13	1.38		11,620	4.11	1.44	<0.001	0.12
MPI-punish	7075	1.57	1.32	9287	1.71	1.36	7705	1.80	1.40		10,720	1.94	1.48	<0.001	0.26^a
MPI-protect	7027	2.96	1.44	9237	3.00	1.43	7666	3.00	1.44		10,681	3.08	1.50	<0.001	0.08
MPI-distract	7064	2.52	1.23	9264	2.55	1.23	7688	2.56	1.22		10,712	2.60	1.27	0.001	0.06
MPI-GAI	7833	2.43	0.92	10,227	2.40	0.90	8395	2.35	0.88		11,672	2.25	0.91	<0.001	0.20^a
EQ-5D-index	7593	0.30	0.32	9915	0.26	0.31	8103	0.23	0.32		11,270	0.16	0.30	<0.001	0.45^a
EQ-VAS	7421	45.85	21.26	9759	42.22	19.87	7985	39.88	19.56		11,052	35.44	19.22	<0.001	0.52^b
sf36-pf	7708	58.13	23.15	10,015	54.22	21.91	8237	49.96	21.21		11,444	43.10	20.41	<0.001	0.70^b
sf36-rp	7543	18.64	30.57	9830	14.54	26.49	8092	12.30	24.34		11,198	9.32	21.01	<0.001	0.37^a
sf36-bp	7719	27.24	16.20	10,010	24.80	14.69	8249	22.71	13.80		11,459	19.51	13.61	<0.001	0.53^b
sf36-gh	7613	49.62	21.42	9884	43.66	20.37	8123	38.09	19.38		11,300	31.13	18.46	<0.001	0.94^c
sf36-vt	7693	33.21	20.90	9982	26.58	18.74	8215	21.96	17.49		11,426	17.11	16.34	<0.001	0.88^c
sf36-sf	7723	53.56	27.27	10,007	48.83	26.29	8229	45.27	25.40		11,451	39.89	24.52	<0.001	0.53^b
sf36-re	7446	48.50	43.93	9686	44.17	43.40	7965	41.80	43.23		11,047	36.25	42.21	<0.001	0.29^a
sf36-mh	7687	58.63	22.44	9976	55.40	22.06	8198	53.51	22.38		11,414	49.73	22.78	<0.001	0.39^a

Notes: ^aSmall effect ES. ^bMedium Effect ES. ^cLarge Effect ES.

Abbreviations: ES, effect size; NRS-7days, pain intensity previous seven days; HAD, Hospital Anxiety and Depression Scale; HAD-A, subscale anxiety; HAD-D, subscale depression; MPI, multidimensional pain inventory: MPI-pain-sever, subscale pain severity; MPI-pain-interfer, subscale pain related Interference; MPI-control, subscale life control; MPI-distress, subscale affective distress; MPI-socsupp, subscale social support; MPI-punish, subscale punishing responses; MPI-protect, subscale protective responses; MPI-distract, subscale distracting responses; MPI-GAI, subscale general activity index; EQ, European Quality of Life instrument; EQ-5D-index, index based on five dimensions; EQ-VAS, self-estimation of health; sf36, short form health survey; sf36-pf, physical functioning; sf36-rp, role limitations due to physical functioning; sf36-bp, bodily pain; sf36-gh, general health; sf36-vt, vitality; sf36-sf, social functioning; sf36-re, role limitations due to emotional problems; sf36-mh=mental health.

Table 3 OPLS Regression of Number of Pain Regions (1–36I) Using Background Variables and the 22 Mandatory Variables at Baseline as Regressors. Note that variable Days with no work or studies was not entered in the regression due to low N.

Variables	VIPpred	p(corr)
sf36-gh^*	1.83	−0.67
sf36-vt^*	1.60	−0.59
Gender^*	1.44	−0.53
sf36-pf^*	1.40	−0.51
MPI-pain-sever^*	1.34	0.49
NRS-7days^*	1.28	0.47
MPI-pain-interfer^*	1.23	0.45
Pain duration^*	1.20	0.43
sf36-bp^*	1.16	−0.43
MPI-control^*	1.11	−0.41
EQ-VAS^*	1.09	−0.40
sf36-sf^*	1.07	−0.40
HAD-A	1.07	0.39
HAD-D	1.04	0.38
MPI-distress	1.00	0.37
EQ-5D-index	0.99	−0.37
sf36-mh	0.96	−0.36
sf36-rp	0.67	−0.24
sf36-re	0.57	−0.21
MPI-punish	0.45	0.16
MPI-GAI	0.44	−0.16
Outside-Europe	0.39	0.14
MPI-protect	0.32	0.12
Health-care seeking	0.31	0.12
University	0.28	−0.10
MPI-distract	0.22	0.08
MPI-socsupp	0.12	−0.04
Age	0.06	0.02
R^2	0.26
Q^2	0.26
CV-ANOVA p-value	<0.001
N	38,369

Notes: VIP (VIP >1.0 is significant) and p(corr) are reported for each regressor ie, the loading of each variable scaled as a correlation coefficient and thus standardizing the range from −1 to +1. A variable/regressor was considered significant when VIP >1.0 and absolute p(corr) ≥0.40. The sign of p(corr) indicates the direction of the correlation with the dependent variable (+ = positive correlation; – = negative correlation). The four bottom rows report R², Q², p-value of the CV-ANOVA, and number of subjects included in the regression (N). *Significant variables.

Abbreviations: Gender, female=0 and male=1; NRS-7 days, pain intensity previous seven days; HAD, Hospital Anxiety and Depression Scale; HAD-A, subscale anxiety; HAD-D, subscale depression; MPI, multidimensional pain inventory: MPI-pain-sever, subscale pain severity; MPI-pain-interfer, subscale pain related interference; MPI-control, subscale life control; MPI-distress, subscale affective distress; MPI-socsupp, subscale social support; MPI-punish, subscale punishing responses; MPI-protect, subscale protective responses; MPI-distract, subscale distracting responses; MPI-GAI, subscale general activity index; EQ, European Quality of Life instrument; EQ-5D-index, index based on five dimensions; EQ-VAS, self-estimation of health; sf36, short form health survey; sf36-pf, physical functioning; sf36-rp, role limitations due to physical functioning; sf36-bp, bodily pain; sf36-gh, general health; sf36-vt, vitality; sf36-sf, social functioning; sf36-re, role limitations due to emotional problems; sf36-mh, mental health; University, education level dichotomized, ie university vs lower levels; Outside-Europe, country of birth dichotomized ie outside Europe vs other areas; Health-care seeking, number of visits to a physician in recent 12 months in three categories.

Table 4 Changes in the 22 Mandatory Outcome Variables Pre vs 12-month Follow-up (Mean and Standard Deviation; a Positive Value Indicates Improvement) by the Four Categories Based on Spreading of Pain. Group Comparison (ANOVA, p-value) are to the Far Right

Category	1–6	Regions		7–12	Regions		13–18	Regions		19–36	Regions		Statistics
Variables	N	Mean	SD	N	Mean	SD	N	Mean	SD	N	Mean	SD	p-value
NRS-7days	1671	1.36	2.39	2378	1.16	2.32	1977	0.96	2.15	2498	0.84	2.04	<0.001
HAD-A	1717	1.22	3.89	2445	1.30	4.00	2040	1.38	4.18	2590	1.47	4.19	0.203
HAD-D	1719	1.48	4.08	2448	1.45	4.03	2039	1.48	4.09	2588	1.41	4.17	0.924
MPI-pain-sever	1719	0.86	1.33	2457	0.69	1.21	2056	0.63	1.12	2602	0.52	1.03	<0.001
MPI-pain-interfer	1699	0.83	1.26	2440	0.64	1.16	2037	0.59	1.13	2588	0.46	1.03	<0.001
MPI-control	1710	0.53	1.33	2447	0.51	1.26	2048	0.51	1.27	2595	0.49	1.28	0.814
MPI-distress	1717	0.54	1.47	2451	0.53	1.41	2052	0.49	1.46	2599	0.43	1.40	0.030
MPI-socsupp	1700	−0.51	1.18	2433	−0.43	1.15	2041	−0.36	1.14	2587	−0.35	1.16	<0.001
MPI-punish	1499	0.01	1.19	2128	0.00	1.13	1816	0.05	1.26	2327	−0.02	1.32	0.442
MPI-protect	1496	−0.17	1.15	2118	−0.23	1.16	1806	−0.17	1.15	2310	−0.15	1.22	0.113
MPI-distract	1498	−0.05	1.05	2126	−0.13	1.08	1811	−0.03	1.06	2322	−0.05	1.11	0.020
MPI-GAI	1712	0.24	0.87	2442	0.17	0.80	2051	0.13	0.80	2585	0.13	0.78	<0.001
EQ-5D-index	1770	0.23	0.35	2486	0.19	0.37	2005	0.16	0.36	2482	0.13	0.35	<0.001
EQ-VAS	1712	12.98	24.32	2420	11.79	23.78	1950	10.42	23.58	2426	9.36	23.68	<0.001
sf36-pf	1659	9.52	19.28	2334	7.07	18.13	1947	5.30	18.72	2454	5.47	18.09	<0.001
sf36-rp	1630	21.94	42.28	2294	15.05	39.25	1905	14.25	36.44	2408	9.77	32.81	<0.001
sf36-bp	1659	14.68	21.37	2328	11.50	20.07	1946	9.66	18.27	2460	8.60	17.48	<0.001
sf36-gh	1636	4.70	19.63	2304	4.63	19.42	1907	5.26	19.21	2433	4.60	18.73	0.663
sf36-vt	1653	9.93	22.96	2329	10.72	23.28	1937	9.42	22.84	2458	8.03	22.18	0.001
sf36-sf	1658	11.26	27.78	2333	9.37	26.93	1940	8.68	27.04	2463	6.47	26.72	<0.001
sf36-re	1594	12.11	51.16	2257	12.44	50.13	1874	10.38	49.39	2374	9.00	48.08	0.078
sf36-mh	1653	6.56	21.44	2327	7.08	20.98	1934	6.14	21.69	2458	5.79	21.26	0.190

Abbreviations: NRS-7d, pain intensity previous seven days; HAD, Hospital Anxiety and Depression Scale; HAD-A, subscale anxiety; HAD-D, subscale depression; MPI, multidimensional pain inventory: MPI-pain-sever, subscale pain severity; MPI-pain-interfer, subscale pain related interference; MPI-control, subscale life control; MPI-distress, subscale affective distress; MPI-socsupp, subscale social support; MPI-punish, subscale punishing responses; MPI-protect, subscale protective responses; MPI-distract, subscale distracting responses; MPI-GAI, subscale general activity index; EQ, European Quality of Life instrument; EQ-5D-index, index based on five dimensions; EQ-VAS, self-estimation of health; sf36, short form health survey; sf36-pf, physical functioning; sf36-rp, role limitations due to physical functioning; sf36-bp, bodily pain; sf36-gh, general health; sf36-vt, vitality; sf36-sf, social functioning; sf36-re, role limitations due to emotional problems; sf36-mh, mental health.