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*
| Variable | Unadjusted | Adjusted | ||||||
| Studies | Participants | Interaction MD (95% CI) | P value | Studies | Participants | Interaction MD (95% CI) | P value | |
| Age (years) | 26 | 3091 | 0.09 (−0.05 to 0.23) | 0.22 | 26 | 3091 | 0.09 (−0.05 to 0.23) | 0.22 |
| Sex | 26 | 3095 | 26 | 3091 | ||||
| Male | − | − | − | − | ||||
| Female | −0.98 (−4.49 to 2.53) | 0.59 | −0.96 (−4.39 to 2.46) | 0.58 | ||||
| High school education | 12 | 1401 | 12 | 1399 | ||||
| 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 smoker | 9 | 1411 | 9 | 1407 | ||||
| No | − | − | − | − | ||||
| Yes | 2.07 (−3.15 to 7.29) | 0.44 | 1.38 (−3.86 to 6.63) | 0.61 | ||||
| Regular physical activity | 11 | 1695 | 11 | 1693 | ||||
| No | − | − | − | − | ||||
| Yes | −1.05 (−5.79 to 3.68) | 0.66 | −0.67 (−5.4 to 4.06) | 0.78 | ||||
| BMI | 17 | 2173 | 0.23 (−0.27 to 0.74) | 0.37 | 17 | 2170 | 0.22 (−0.27 to 0.71) | 0.38 |
| History of LBP | 8 | 827 | 8 | 827 | ||||
| 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) | 14 | 1578 | 14 | 1575 | ||||
| No | − | − | − | − | ||||
| Yes | −2.27 (−9.15 to 4.61) | 0.52 | −2.15 (−8.92 to 4.62) | 0.53 | ||||
| Work status | 18 | 2446 | 18 | 2444 | ||||
| Unemployed | − | − | − | − | ||||
| Employed | −3.81 (−9.07 to 1.45) | 0.16 | −4.22 (−9.26 to 0.82) | 0.10 | ||||
| Heavy physical demands | 8 | 1388 | 8 | 1386 | ||||
| No | − | − | − | − | ||||
| Yes | 4.45 (−1.84 to 10.74) | 0.17 | 4.92 (−1.35 to 11.19) | 0.12 | ||||
| General health (0–100) | 10 | 1319 | 0.05 (−0.11 to 0.20) | 0.54 | 10 | 1316 | 0.05 (−0.11 to 0.21) | 0.55 |
| Mental health (0–100) | 6 | 877 | −0.05 (−0.19 to 0.10) | 0.54 | 6 | 874 | −0.04 (−0.18 to 0.11) | 0.61 |
| Fear avoidance beliefs (0–100) | 8 | 1012 | 0.08 (−0.03 to 0.20) | 0.16 | 8 | 1011 | 0.09 (−0.03 to 0.20) | 0.15 |
| Social support | 10 | 1451 | 10 | 1450 | ||||
| No | − | − | − | − | ||||
| Yes | −1.05 (−5.65 to 3.55) | 0.66 | −1.38 (−5.97 to 3.20) | 0.55 | ||||
| Episode duration (months) | 13 | 1572 | 0.02 (−0.03 to 0.07) | 0.37 | 13 | 1569 | 0.02 (−0.04 to 0.08) | 0.58 |
| Functional limitations (0–100) | 24 | 2880 | 0.01 (−0.08 to 0.11) | 0.81 | 24 | 2876 | 0.02 (−0.07 to 0.12) | 0.66 |
| Pain intensity (0–100) | 26 | 3095 | −0.06 (−0.15 to 0.03) | 0.23 | 26 | 3091 | −0.05 (−0.14 to 0.04) | 0.26 |
| Any leg pain | 14 | 1837 | 14 | 1833 | ||||
| No | − | − | − | − | ||||
| Yes | 1.60 (−3.57 to 6.77) | 0.54 | 1.46 (−3.73 to 6.64) | 0.58 | ||||
| Any LBP medication use | 13 | 1776 | 13 | 1774 | ||||
| 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.