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] |