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STUDY DESIGN. Exploratory subgroup analysis in a randomized controlled trial (RCT). OBJECTIVE. To detect possible moderators in the effectiveness of a workplace intervention in a population of workers with sick leave due to sub acute nonspecific low back pain. SUMMARY OF BACKGROUND DATA. In a recently published RCT, a workplace intervention was effective on return to work, compared to usual care. Examining the heterogeneity of effect sizes within the population in this RCT (n = 196) can lead to information on the effectiveness of the intervention in subgroups of patients. METHODS. A subgroup analysis was performed by adding interaction terms to the statistical model. Before analysis the following possible moderators for treatment were identified: age, gender, pain, functional status, heavy work, and sick leave in the previous 12 months. Cox regression analyses were performed and survival curves were plotted. RESULTS. The interaction (P = 0.02) between age (dichotomized at the median value) and the workplace intervention indicates a modifying effect. The workplaceintervention is more effective for workers <44 years (HR, 95% CI = 2.5, [1.6, 4.1] vs. 1.2 [0.8, 1.8] for workers <44 years old). The interaction between sick leave in the previous 12 months and the workplace intervention is significant (P = 0.02). The intervention is more effective for workers with previous sick leave (HR, 95% CI = 2.8 [1.7, 4.9] vs. 1.3 [0.8, 2.0]). A modifying effect of gender, heavy work, and pain score and functional status on the effectiveness of this intervention was not found. CONCLUSION. The findings from these exploratory analyses should be tested in future RCTs. This workplace intervention seems very suitable for return to work of older workers and workers with previous sick leave. Gender, perceived heavy work, and baseline scores in pain and functional status should not be a basis for assignment to this intervention. © 2009 Lippincott Williams & Wilkins, Inc.

To assess the effectiveness of workplace intervention and graded activity, separately and combined, for multidisciplinary rehabilitation of low back pain (LBP). Summary of Background Data. Effective components for multidisciplinary rehabilitation of LBP are not yet established. Methods: Participants sick-listed 2 to 6 weeks due to nonspecific LBP were randomized to workplace intervention (n = 96) or usual care (n = 100). Workplace intervention consisted of workplace assessment, work modifications, and case management involving all stakeholders. Participants still sick-listed at 8 weeks were randomized for graded activity (n = 55) or usual care (n = 57). Graded activity comprised biweekly 1-hour exercise sessions based on operant-conditioning principles. Outcomes were lasting return to work, pain intensity and functional status, assessed at baseline, and at 12, 26, and 52 weeks after the start of sick leave. Results: Time until return to work for workers with workplace intervention was 77 versus 104 days (median) for workers without this intervention (P = 0.02). Workplace intervention was effective on return to work (hazard ratio = 1.7; 95% CI, 1.2-2.3; P = 0.002). Graded activity had a negative effect on return to work (hazard ratio = 0.4; 95% CI, 0.3-0.6; P < 0.001) and functional status. Combined intervention had no effect. Conclusion: Workplace intervention is advised for multidisciplinary rehabilitation of subacute LBP. Graded activity or combined intervention is not advised.

BACKGROUND: The percentages of patients with acute low back pain (LBP) that go on to a chronic state varies between studies from 2% to 34%. In some of these cases low back pain leads to great costs. AIMS: To evaluate the evidence for prognostic factors for return to work among workers sick listed with acute LBP. METHODS: Systematic literature search with a quality assessment of studies, assessment of levels of evidence for all factors, and pooling of effect sizes. RESULTS: Inclusion of studies in the review was restricted to inception cohort studies of workers with LBP on sick leave for less than six weeks, with the outcome measured in absolute terms, relative terms, survival curve, or duration of sick leave. Of the studies, 18 publications (14 cohorts) fulfilled all inclusion criteria. One low quality study, four moderate quality studies, and nine high quality studies were identified; 79 prognostic factors were studied and grouped in eight categories for which the evidence was assessed. CONCLUSIONS: Specific LBP, higher disability levels, older age, female gender, more social dysfunction and more social isolation, heavier work, and receiving higher compensation were identified as predictors for a longer duration of sick leave. A history of LBP, job satisfaction, educational level, marital status, number of dependants, smoking, working more than 8 hour shifts, occupation, and size of industry or company do not influence duration of sick leave due to LBP. Many different constructs were measured to identify psychosocial predictors of long term sick leave, which made it impossible to determine the role of these factors

BACKGROUND: The percentages of patients with acute low back pain (LBP) that go on to a chronic state varies between studies from 2% to 34%. In some of these cases low back pain leads to great costs. AIMS: To evaluate the evidence for prognostic factors for return to work among workers sick listed with acute LBP. METHODS: Systematic literature search with a quality assessment of studies, assessment of levels of evidence for all factors, and pooling of effect sizes. RESULTS: Inclusion of studies in the review was restricted to inception cohort studies of workers with LBP on sick leave for less than six weeks, with the outcome measured in absolute terms, relative terms, survival curve, or duration of sick leave. Of the studies, 18 publications (14 cohorts) fulfilled all inclusion criteria. One low quality study, four moderate quality studies, and nine high quality studies were identified; 79 prognostic factors were studied and grouped in eight categories for which the evidence was assessed. CONCLUSIONS: Specific LBP, higher disability levels, older age, female gender, more social dysfunction and more social isolation, heavier work, and receiving higher compensation were identified as predictors for a longer duration of sick leave. A history of LBP, job satisfaction, educational level, marital status, number of dependants, smoking, working more than 8 hour shifts, occupation, and size of industry or company do not influence duration of sick leave due to LBP. Many different constructs were measured to identify psychosocial predictors of long term sick leave, which made it impossible to determine the role of these factors