Sex Differences in Predictors of Outcome in Selected Physical Therapy Interventions for Acute Low Back Pain

Abstract

Secondary analysis of pooled data from 3 randomized trials. This study investigated sex differences in response to physical therapy intervention for acute low back pain. Sex differences in experimental pain sensitivity have been consistently described in the literature. However, clinical consequences of these sex differences have not been widely reported. Subjects (n=165) were participants in 3 randomized trials of physical therapy interventions from outpatient physical therapy clinics in the general and military communities. Subjects were randomly assigned spinal manipulation with range-of-motion exercise, lumbar stabilization exercise, or directional-preference exercise. Outcomes were measured at 4 weeks through self-report of pain intensity and pain-related disability. Sex differences were investigated with independent t tests (baseline data), 2 x 3 analysis of variance (4-week reductions in pain and pain-related disability), and regression models (predictors of outcome). Men and women had similar reductions of pain intensity (raw mean difference, 0.5; 95% Cl, -1.4 to 0.4) and pain-related disability (raw mean difference, 5.3; 95% CI, -0.1 to 10.7) over 4 weeks. Baseline pain intensity, duration of symptoms, and baseline pain-related disability significantly predicted change in pain intensity for women (r2 = 26%, P < .01). Baseline pain intensity and stabilization exercise predicted change in pain intensity for men (r2 = 33%, P<.01). Baseline pain-related disability, duration of pain, and pain intensity predicted change in disability for women (r2 = 24%, P < .01). Baseline pain-related disability, fear-avoidance beliefs, stabilization exercise, and leg pain predicted change in disability for men (r2 = 32%, P < .01). For patients with acute low back pain, men and women had similar physical therapy outcomes for reductions in pain intensity and pain-related disability. However, men and women had different factors that predicted treatment outcome.