Table 6

Size and statistical significance of treatment–variable interactions (unadjusted and adjusted results) on important global recovery in pain or functional outcome (dichotomous) at follow-up closest to 3 months*

VariableUnadjustedAdjusted
Studies (n)Participants (n)Interaction
OR (95% CI)
P valueStudies (n)Participants (n)Interaction
OR (95% CI)
P value
Age (years)2529951.01 (0.99 to 1.02)0.432529951.01 (0.99 to 1.02)0.43
Sex252995252995
 Male
 Female1.33 (0.91 to 1.94)0.151.32 (0.90 to 1.93)0.16
High school education101204101202
 High school or less
 Beyond high school1.32 (0.73 to 2.40)0.361.32 (0.72 to 2.40)0.37
Current smoker9142191417
 No
 Yes0.98 (0.54 to 1.80)0.961.04 (0.56 to 1.93)0.90
Regular physical activity121758121756
 No
 Yes0.94 (0.56 to 1.57)0.800.90 (0.54 to 1.52)0.70
BMI1519860.95 (0.89 to 1.00)0.0671519830.95 (0.89 to 1.00)0.054
History of LBP88308830
 No
 Yes1.05 (0.40 to 2.79)0.921.05 (0.39 to 2.78)0.93
Sick leave (past 12 months)131450131447
 No
 Yes1.33 (0.61 to 2.92)0.481.26 (0.57 to 2.80)0.56
Work status172319172317
 Unemployed
 Employed0.93 (0.56 to 1.55)0.780.94 (0.56 to 1.58)0.82
Heavy physical demands8139381391
 No
 Yes0.56 (0.26 to 1.21)0.140.55 (0.26 to 1.19)0.13
General health (0–100)1013351.00 (0.98 to 1.03)0.881013321.00 (0.98 to 1.03)0.92
Mental health (0–100)79540.99 (0.97 to 1.02)0.5579510.99 (0.97 to 1.01)0.46
Fear avoidance beliefs (0–100)911061.00 (0.98 to 1.01)0.69911051.00 (0.98 to 1.01)0.71
Social support9138091379
 No
 Yes1.14 (0.66 to 1.97)0.641.17 (0.67 to 2.02)0.58
Episode duration (months)1315751.00 (1.00 to 1.01)0.411315721.00 (1.00 to 1.01)0.43
Functional limitations (0–100)2529991.01 (1.00 to 1.02)0.282529951.01 (0.99 to 1.02)0.32
Pain intensity (0–100)2429251.00 (0.99 to 1.01)0.792429211.00 (0.99 to 1.01)0.81
Any leg pain151950151946
 No
 Yes0.98 (0.54 to 1.78)0.951.01 (0.55 to 1.86)0.97
Any LBP medication use131795131793
 No
 Yes1.72 (1.03 to 2.85)0.0371.68 (1.01 to 2.81)0.046
  • An interaction coefficient above 1 indicates increased likelihood of recovery 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 functional limitations, 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.