A total of 1254 clinicians in the study region were identified and contacted. Of these, 170 (73 general medical practitioners, 77 physiotherapists, and 20 chiropractors) worked in primary care, agreed to participate, and were trained in the study protocol. The trained clinicians screened 3184 consecutive patients with low back pain from November 2003 to July 2005. Of these, 973 patients (mean age 43.3, 54.8% men) had non-specific low back pain of less than two weeks’ duration and were thus eligible to participate (fig 1). Figure 1 also shows reasons for ineligibility. Data on individual items of the baseline questionnaire were missing for four participants (0.4%). As few data were missing, we excluded participants with missing baseline data from all analyses. The follow-up rate remained above 97% over the 12 month period. Participants for whom we did not have complete follow-up data and who had not reported recovery from their low back pain were censored at the time of their last follow-up.
Fig 1 Flowchart of participants through study
Table 1 shows baseline demographic and clinical features of participants. We used the participant’s postcode and data from the Australian census to judge socioeconomic disadvantage: 21.4% fell in the most disadvantaged quarter, 8.4% in the second quarter, 14.8% in the third quarter, and 55.1% in the fourth quarter.
Table 1 Baseline characteristics of eligible participants. Figures are numbers (percentages) of patients unless stated otherwise
There were 770 (79.5%) participants who reported working before the onset of their episode of acute low back pain. Of these, 291 (37.8% of workers, 30.0% of the total cohort) reported changing their work status as a result of their low back pain. The median time to return to previous work hours and duties for these 291 participants was 14 days (95% confidence interval 11 to 17 days). Kaplan-Meier curves (see bmj.com) showed that the cumulative probability of returning to pre-back pain work hours and duties for those who reduced their work status at baseline because of low back pain was 74.6% at six weeks, 83.2% at 12 weeks, and 89.5% one year after consulting a primary care clinician for acute low back pain.
The median time to recovery in terms of disability was 31 days (25 to 37 days). By six weeks the cumulative probability of having no disability was 54.9%. This probability increased to 73.3% by 12 weeks, and 83.3% by one year. The median time to recovery in terms of pain after an episode of acute low back pain was 58 days (53 to 63 days). The cumulative probability of being pain-free was 39.9% by six weeks, 58.2% by 12 weeks, and 72.5% by one year. See bmj.com for further details.
Complete recovery from recent onset low back pain, determined by recovery on all three dimensions (return to work, no disability, and no pain) took a median time of 59 days (53 to 65 days). Six weeks after presentation to primary care, the cumulative probability of recovery was 39.0%. By 12 weeks the probability was 57.4%, and this increased to 71.8% by one year (fig 2).
Fig 2 Kaplan-Meier estimate of time to complete recovery, determined by phone follow-up at six weeks, three months, and 12 months. Participants were interviewed to establish if they had recovered (no pain for one month AND no disability for one month (more ...)
Table 2 shows pain, disability, and work status assessed at study entry and each follow-up. At six weeks, three months, and 12 months, 40%, 52%, and 57% of participants reported being pain-free; 60%, 71%, and 75% reported being disability-free. Immediately before the onset of the episode 77% were working full time and this reduced to 48% at baseline, rising to 69%, 72%, and 72% at six weeks, three months, and 12 months. At 12 months the participants’ responses to the question “If you had to live with the symptoms you have right now, how would you feel about it?” were generally positive, though 133 of the 969 participants reported feeling very dissatisfied and 106 somewhat dissatisfied.
Table 2 Pain, disability, and work status of 969 participants immediately before onset of episode and at study entry, six weeks, three months, and 12 months. Figures are numbers (percentages) of participants
Full results for the univariate Cox regression analyses are on bmj.com. Cultural variables were not significantly associated with time to recovery. After adjustment for age, sex, intensity of pain, and interference with function, psychological characteristics were most closely associated with time to recovery (χ2=81.51, P<0.001). Of the other factors, only factors related to current history further contributed significantly to the model (χ2=36.72, P≤0.001, table 3). Seven individual variables were independently associated with time to recovery: age, intensity of pain, feelings of depression, risk of persistence, low back pain in compensation cases, days of reduced activity, and duration of the episode.
Table 3 Cox regression model for time to complete recovery from acute low back pain (LBP) with hazard ratios (HR) and 95% confidence intervals