Table 4

Size and statistical significance of treatment–variable interactions (unadjusted and adjusted results) on continuous pain outcome (0–100) at follow-up closest to 3 months*

VariableUnadjustedAdjusted
StudiesParticipantsInteraction
MD (95% CI)
P valueStudiesParticipantsInteraction
MD (95% CI)
P value
Age (years)2630910.09 (−0.05 to 0.23)0.222630910.09 (−0.05 to 0.23)0.22
Sex263095263091
 Male
 Female−0.98 (−4.49 to 2.53)0.59−0.96 (−4.39 to 2.46)0.58
High school education121401121399
 High school or less
 Beyond high school−3.94 (−8.90 to 1.02)0.12−3.69 (−8.65 to 1.27)0.15
Current smoker9141191407
 No
 Yes2.07 (−3.15 to 7.29)0.441.38 (−3.86 to 6.63)0.61
Regular physical activity111695111693
 No
 Yes−1.05 (−5.79 to 3.68)0.66−0.67 (−5.4 to 4.06)0.78
BMI1721730.23 (−0.27 to 0.74)0.371721700.22 (−0.27 to 0.71)0.38
History of LBP88278827
 No
 Yes−4.03 (−13.88 to 5.82)0.42−3.92 (−13.76 to 5.92)0.44
Sick leave (past 12 months)141578141575
 No
 Yes−2.27 (−9.15 to 4.61)0.52−2.15 (−8.92 to 4.62)0.53
Work status182446182444
 Unemployed
 Employed−3.81 (−9.07 to 1.45)0.16−4.22 (−9.26 to 0.82)0.10
Heavy physical demands8138881386
 No
 Yes4.45 (−1.84 to 10.74)0.174.92 (−1.35 to 11.19)0.12
General health (0–100)1013190.05 (−0.11 to 0.20)0.541013160.05 (−0.11 to 0.21)0.55
Mental health (0–100)6877−0.05 (−0.19 to 0.10)0.546874−0.04 (−0.18 to 0.11)0.61
Fear avoidance beliefs (0–100)810120.08 (−0.03 to 0.20)0.16810110.09 (−0.03 to 0.20)0.15
Social support101451101450
 No
 Yes−1.05 (−5.65 to 3.55)0.66−1.38 (−5.97 to 3.20)0.55
Episode duration (months)1315720.02 (−0.03 to 0.07)0.371315690.02 (−0.04 to 0.08)0.58
Functional limitations (0–100)2428800.01 (−0.08 to 0.11)0.812428760.02 (−0.07 to 0.12)0.66
Pain intensity (0–100)263095−0.06 (−0.15 to 0.03)0.23263091−0.05 (−0.14 to 0.04)0.26
Any leg pain141837141833
 No
 Yes1.60 (−3.57 to 6.77)0.541.46 (−3.73 to 6.64)0.58
Any LBP medication use131776131774
 No
 Yes−4.04 (−9.66 to 1.58)0.16−3.90 (−9.40 to 1.60)0.16
  • A negative interaction coefficient indicates decreased pain for the variable level (eg, female) with exercise vs any non-exercise comparison (ie, all other conservative and no treatment/usual care comparisons.

  • *Unadjusted models include baseline pain, potential treatment effect-modifying variable, treatment group (exercise or comparison treatment), and trial at the random-effects level and the variable–treatment group interaction at the fixed-effects level. Adjusted models add age and sex (at the random-effects level). All participant-level covariates are centred around their trial-specific means.

  • BMI, body mass index; LBP, low back pain; MD, mean difference.