Table 4.

Between-group comparisons on primary and secondary outcomes at 24-month follow-up (ANCOVA)

		IG (N = 189) M+ (95% CI)	CG (N = 255) M+ (95% CI)	Between group
				p	Cohen’s d* [95% CI]
Primary outcomes
Back pain severity (CPGQ)	characteristic pain intensity (0–100)	38.7 (36.2–41.2)	41.5 (39.3–43.6)	0.110	−0.16 [− 0.34 to 0.03]
	disability points (0–6)	1.6 (1.4–1.8)	2.0 (1.8–2.2)	0.025	−0.24 [− 0.43 to − 0.05]
Health-related quality of life (SF-12)	physical component (0–100)	43.3 (42.0–44.5)	41.0 (39.9–42.0)	0.007	0.26 [0.07 to 0.45]
	mental component (0–100)	46.9 (45.5–48.3)	46.7 (45.5–48.0)	0.855	0.02 [−0.21 to 0.17]
Secondary outcomes
Psychological distress (PHQ-4)	sum score (0–12)	2.7 (2.4–3.1)	3.2 (2.9–3.4)	0.040	−0.24 [− 0.42 to − 0.05]
Risk of chronifi-cation (STarT-G)	total score (0–9)	2.6 (2.3–2.8)	3.0 (2.8–3.3)	0.009	− 0.25 [− 0.44 to − 0.07]
Physical activitya	days per week with at least 10 min physical activity (0–7)	2.7 (2.5–2.9)	2.4 (2.2–2.6)	0.028	0.21 [0.03 to 0.40]

IG intervention group, CG Control group, p significance value; M⁺: values of the group means adjusted for baseline-score, StarT-G total risk score and satisfaction with medical care of back pain at baseline, CI Confidence interval; CPGQ Chronic Pain Grade Questionnaire; SF-12: Short Form 12; PHQ-4: Patient Health Questionnaire 4; STarT-G: Keele STarT back Screening Tool, German Version

^aphysically active in a way that one starts to sweat or gets out of breath

Cohen’s d*: if higher scores of the outcome parameter describe worse health condition (e.g. GCPS-parameters), minus d means IG is superior to CG and plus d means IG is worse than CG; if higher scores describe better health conditions (e.g. SF-12 parameters), minus d signifies IG is inferior to CG and plus d means IG is better than CG