Demographic and clinical characteristics associated with failure of physical therapy in chronic low back pain: a secondary analysis from a randomized controlled trial

BACKGROUND: The effect of physical therapy on pain and disability alleviation in patients with chronic low back pain (cLBP) has been demonstrated, but the risk factors for treatment failure remain unknown. AIM: To explore the associations of baseline demographic and clinical characteristics with treatment failure after physical therapy intervention for cLBP. DESIGN: A secondary analysis of a single-blind randomized clinical trial. SETTING: A rehabilitation hospital. POPULATION: A total of 98 patients with cLBP completed the 12-month measurement. METHODS: Patients were randomly grouped into 3-month therapeutic aquatic exercise or physical therapy modalities. The primary outcome was treatment failure, which was defined as a decrease in the numeric rating scale to less than 2.0 points at 12-month follow-up. Associations between baseline demographic and clinical characteristics with risk of treatment failure were assessed by logistic regressions. RESULTS: The pain intensity in the failure cases was alleviated after 3-month intervention but continuously increased at 6- and 12-month followup (P<0.05). Old age was significantly associated with an increased risk of treatment failure (adjusted OR 3.26, 95% CI 1.11–9.60). Compared with those receiving physical therapy modalities, the patients receiving therapeutic aquatic exercise had less risk of treatment failure (adjusted OR 0.19, 95% CI 0.08–0.47), and age (P=0.022) was a modifier for this association. CONCLUSIONS: Compared with younger ones, older patients with cLBP had a higher risk of treatment failure after physical therapy and gained a stronger benefit of long-term pain alleviation from therapeutic aquatic exercise. CLINICAL REHABILITATION IMPACT: Therapeutic aquatic exercise is an effective therapy for cLBP and more helpful for preventing treatment failure than physical therapy modalities, especially for older patients.