Predictors of response to exercise therapy for chronic low back pain: result of a prospective study with one year follow-up.

BACKGROUND: Low back pain (LBP) management is a critical public health issue in all developed countries. Most approaches show evidence of effects only in the short term. AIM: To identify predictors of functional outcome on discharge and at 1 year.
DESIGN: Prospective cohort study.
SETTING: Outpatient rehabilitation department. POPULATION: Patients aged >18 addressed to exercise therapy for persisting LBP.
METHODS: The individually designed physiotherapy program provided 7 sessions (45'); patients were given advice to stay active and continue exercise program on discharge. Baseline (T0) assessment included: age, sex, time since onset, pain-related drug use, previous treatments, job, physical activity, pain (NRS) and Mental Health (SF36 sub-score); at follow-up (T2), we also enquired to on adherence to exercise prescription, physical activity, drugs. The primary outcome measure was the Roland and Morris Disability Questionnaire (RMDQ) patients scoring improvement >30% (minimal clinical important difference) were classified as respondent.
RESULTS: 211 completed follow-up (70% women; age 70.4±11.9). Average RMDQ score was reduced by 35% at T1 and by 31% at T2; NRS by 28% (T1) and 24% (T2); 125 patients (59%) were responders on discharge; 106 (50%) at follow-up. Only higher baseline NRS predicted poor response to treatment at T1 (OR=0.83, 95% CI: 0.71-0.95, P=0.012)). At T2, older age (OR=0.94, 95% CI: 0.91-0.98, P=0.003), drug use (OR=0.18, 95% CI: 0.08-4,69, P<0.001) and previous treatments (OR 0.33, 95% CI: 0.15 to 0.71, P=0.004) were significantly associated with poor response, while, baseline mental health (OR=1.1, 95% CI: 1.01-1.24, P=0.02) and adherence to exercises for LBP (OR=2.10, 95% CI: 1.03-4.42, P=0.04) predicted improved outcome.
CONCLUSIONS: The individually designed exercise therapy program for chronic LBP was associated to clinically significant functional improvement both on discharge and at 1 year. Only severe pain intensity predicted poor treatment response on discharge. At one year, younger age and better mental health predicted improved outcome, while use of drugs and previous LBP treatments were associated with worse response. Adherence to the exercise program almost doubled the probability of a favorable outcome. CLINICAL REHABILITATION IMPACT: Adherence to an extensive individually designed exercise therapy program improves long term functional outcome of chronic low back pain.