Risk and protective factors in the clinical rehabilitation of chronic back pain

Figures & data

Figure 1 Enrollment of CBP patients (t₁ = beginning of back pain rehabilitation, t₂ = 6 months after back pain rehabilitation).

Abbreviations: CBP, chronic back pain; n, number of participants

Figure 2 CFA using a two-factor model “disability due to pain” (CF-D) and “experience of pain” (CF-PE).

Abbreviations: CFA, confirmatory factor analysis; CPG, Chronic Pain Grade Questionnaire; SF-36, Short-Form Health Survey; WAI, Work Ability Index; BSI, Brief Symptom Inventory; SBL, Schmerzbeschreibungsliste (pain description list); CF-PE, chronification factor pain experience; CF-D, chronification factor disability.

Table 1 Descriptives of participants at baseline (n = 145)

Characteristics of participants	Value M (SD) or n (%)	Questionnaire	Value M (SD) or n (%)
Sociodemography		Pain-related cognition
Age (years)	48.46 (6.37)	FABQ – connection with physical activity	19.40 (6.08)
		FABQ – caused by work	14.41 (7.96)
Gender female	106 (73)	FABQ – prognosis of work resumption	16.28 (8.05)
Marital status (married or long-term relationship)	103 (71)
Health insurance	138 (95)
Education		Emotion
Lower secondary qualifications	19 (13)	HADS – depression	6.59 (4.06)
General secondary qualifications	96 (66)	HADS – anxiety	8.05 (3.70)
		Stress
Comprehensive secondary qualifications	30 (21)	LEs	9.93 (5.45)
		PSS – subjective stress	20.29 (6.13)
Substance abuse		Work stress
Smoking, yes	55 (38)	ERI – balance	0.12 (0.19)
Alcohol, yes	25 (17)	ERI – overcommitment	16.19 (4.35)
Medication, yes	112 (77)
General health behavior		SS (BSSS)
Regular physical activity, yes	55 (38)	BSSS – perceived emotional	3.63 (0.51)
Rehabilitation program, yes	145 (100)	BSSS – perceived instrumental	3.58 (0.59)
General sleep (range 0–10)	4.58 (2.25)
General health (range 0–10)	5.24 (2.8)
WAI	28.82 (7.63)	BSSS – received emotional	3.73 (0.37)
		BSSS – received instrumental	3.59 (0.60)
		BSSS – received informational	3.25 (0.73)
		BSSS – satisfaction with support	3.81 (0.545)

Abbreviations: ERI, Effort–Reward Imbalance questionnaire; FABQ, Fear-Avoidance Beliefs Questionnaire; HADS, Hospital Anxiety and Depression Scale; LE, life event; PSS, Perceived Stress Scale; SS, social support; WAI, Work Ability Index; BSSS, Berlin Social Support Scales.

Table 2 Prediction of CF-PE and CF-D at t₁ (beginning of back pain rehabilitation) using lifestyle/demography, medical care situation and profession

Model	Influencing factors	Disability (CF-D)			Experience of pain (CF-PE)
		β	R^2	Model fit	β	R^2	Model fit
M1	Gender (female)	−0.109	1.2%	F (1,72) = 0.867	−0.325*	10.5%	F (1,96) = 11.31*
M2	Clinic	0.418*	17.5%	F (1,72) = 15.29*	0.364*	13.3%	F (1,96) = 14.68*
M3	Income	−0.222	4.9%	F (1,69) = 3.564*	−0.252*	6.4%	F (1,90) = 6.107*
M4	Seated work	0.270	11.1%	F (2,59) = 3.673	0.238	6.4%	F (2,77) = 2.628
	Demanding physical work	0.404*			0.294*
M5	Smoking (dummy basis: yes)	−0.202	4.1%	F (1,71) = 3.012	−0.251*	6.3%	F (1,95) = 6.401*
M6	General Sleep	−0.259*	6.7%	F (1,70) = 5.033*	−0.327*	10.7%	F (1,91) = 10.92*
M7	PI (according to CPG questionnaire)	0.032	18.2%	F (2,70) = 7.806*	0.331*	15.6%	F (2,93) = 8.612*
	Pain disability (according to CPG questionnaire)	0.408*			0.097

Notes: Results from simple and multiple regression analyses, controlled for age.

* p < 0.05. Standardized regression coefficient (β), explained variance (R²) and the model fit for each tested model. M1–M7 indicate separate models. Influencing factors: gender, clinic, education, profession, income, type of health insurance, availability of medical care structure, duration of medical case history, therapies implemented up to now, seated work, demanding physical work, shift work, physical activity, alcohol intake, smoking, sports participation, general sleep and health, initial pain intensity and disability (operationalized by CPG questionnaire).

Abbreviations: PI, pain intensity; CPG, Chronic Pain Grade; CF-PE, chronification factor pain experience; CF-D, chronification factor disability.

Table 3 Prediction of CF-D and CF-PE at t₁ (beginning of back pain rehabilitation) using lifestyle/demography and profession

Influencing factors	Disability (CF-D)			Experience of pain (CF-PE)
	b	β	p	b	β	p
Intercept	–6.14		<0.01**	–0.97		0.51
Gender (dummy basis: female)	–	–	–	–0.92	–0.22	0.04*
Clinic (dummy basis: clinic 1)	3.67	0.39	<0.01**	2.10	0.36	<0.01**
Income	–	–	–	0.00	0.00	0.98
Demanding physical work	0.33	0.21	0.06+	0.27	0.24	0.02*
Smoking (dummy basis: yes)	–	–	–	–0.98	–0.23	0.02*
General sleep	–0.13	–0.12	0.30	–0.06	–0.08	0.47
PI (according to CPG questionnaire)	–	–		0.02	0.21	0.06+
Pain disability (according to CPG questionnaire)	0.04	0.32	<0.01**	–	–	–

Notes: Multiple regression models: pain experience (CF-PE): R² = 0.365, F (7,66) = 6.99; disability (CF-D): R² = 0.323, F (4,55) = 8.04**; controlled for initial PI and age (CF-PE) respectively initial DS and age (CF-D).

+ p < 0.10,

* p < 0.05,

** p < 0.01.

Abbreviations: PI, pain intensity; CPG, Chronic Pain Grade; CF-PE, chronification factor pain experience; CF-D, chronification factor disability.

Table 4 Results from separate multiple regression analyses predicting CF-PE and CF-D from established and often neglected risk factors of CBP

Model	Factors in models	Disability (CF-D)			Experience of pain (CF-PE)
		β	R^2	Model fit	β	R^2	Model fit
M1	Prognosis of returning to work	0.29*	0.34	F (6,53) = 6.10**	0.23#	0.41	F (8,70) = 7.87**
M2	Depression	0.31**	0.40	F (6,53) = 7.58**	0.18#	0.40	F (8,69) = 6.23**
M3	Perceived emotional support	–0.23#	0.34	F (6,54) = 6.11**	–	–	–
M4	Average intensity of LEs	0.27*	0.28	F (6,48) = 4.53**	0.31**	0.40	F (8, 62) = 6.88**
M5	Effort	–	–	–	0.22*	0.43	F (8,68) = 8.15**
M6	Overcommitment	–	–	–	0.27*	0.45	F (8,68) = 8.76**
M7	ERI	–	–	–	0.20#	0.40	F (8,82) = 6.75

Notes: Standardized regression coefficient (β), explained variance (R²) and the model fit for each tested model; M1–M7 indicate separate models. All analyses for CF-PE were controlled for the factors that had a significant influence on CF-PE in the second set of regression analyses for the time period between t₁ (beginning of back pain rehabilitation) and t₁ (6 months after back pain rehabilitation) (participants’ age, gender, clinic, PI at t₁, physical workload and smoking). All analyses for CF-D controlled for the factors that had a significant influence on CF-SE in the second set of regression analyses for the time period between t₁ and t₂ (participants’ age, clinic, demanding physical work and disability at t₁).

# p < 0.1,

* p < 0.05 and

** p < 0.01.

Abbreviations: CBP, chronic back pain; LE, life event; ERI, Effort–Reward Imbalance questionnaire; PI, pain intensity; CF-PE, chronification factor pain experience; CF-D, chronification factor disability.