• Back disorders
• public health
• health and safety
• ergonomics
• intervention studies
• cancer
• hygiene/occupational hygiene
• epidemiology
• asthma
• PCBs
• dioxins
• urological
• low back pain
• secondary prevention
• RCT
• disability
• occupational setting

In most industrialised countries, the institutions managing the healthcare system are increasingly concerned by rising trends in disability and work loss due to low back pain (LBP). From a public health perspective, a health problem such as LBP, that affects 30%–45% of the adult population annually, would certainly demand primary prevention programs. Although such programs have proven helpful for other prevalent conditions such as cardiovascular diseases, they have not yet been shown to be effective for LBP in spite of a quarter of a century of effort and scientific trials.1 2 While these negative results are not a compelling reason to abandon well-designed multidimensional prevention programs, they do provide public health authorities and medical professionals with a strong incentive to focus preventive efforts on LBP prognostic factors through secondary prevention strategies.

The possible benefits to be gained from secondary prevention have long drawn interest from health professionals and researchers. Since the 1990s innovative rehabilitation programs for workers sicklisted due to LBP have been developed, notably the so-called Sherbrooke model which aims at an early return to work through integration of the workplace in the treatment program.3 Solid evidence is now available to show that this type of workplace-based intervention is more effective than usual healthcare interventions for reducing sick leave and preventing work disability among workers with musculoskeletal disorders.4

However, the effectiveness of a workplace component in these interventions raises many questions and the underlying mechanisms are far from being understood.5 Why in some studies did the intervention in the occupational setting have such an impressive effect on outcomes, while in other studies a workplace visit did not make any difference to the impact of the intervention? In view of their complex biopsychosocial natures, are such interventions easily replicable in any occupational setting?

In this issue of the journal, two randomised controlled trials (RCT) clearly expand our knowledge of the possible benefits of interventions targeting LBP in workers in occupational settings. Both studies have included workers with mild LBP symptoms, and in contrast to the return to work interventions mentioned above, have not selected the workers based on their sick leave status.

In the trial conducted by Jensen et al6 (See page 21), the source population were Danish patients with LBP referred for specialised evaluation at two outpatient rheumatology clinics. These patients had moderate to severe symptoms (about 50% had radiating pain below the knee) but had not been referred for surgery, had expressed concerns about their ability to maintain their current job and were willing to accept a visit at their workplace. The study evaluated the effectiveness of two counselling sessions given 3 months apart by an occupational health physician, with emphasis on experienced workplace barriers and moderate-intensity physical activity for a minimum of 3×45 min a week. In comparison to usual care (114 patients), the intervention group (110 patients) exhibited a reduction in bodily pain and an improvement in self-assessed (by SF-36) physical function and in maximum oxygen uptake; a significant reduction in self-reported sick leave was also observed. A workplace visit only took place in about 25% of cases. As stated by the authors, this could be related to the demographics of the worker population, only about 20% of whom were blue-collar workers with physically demanding tasks. It can be thus hypothesised that the key factor behind the effectiveness of the intervention was the emphasis on the patient's perspective, that is, the counselling which targeted elements that the patient themselves considered to be barriers, which resulted in adherence to defined goals and, in particular, an increase in physical activity. This RCT trial is of great interest as it used a low cost intervention and suggests that a well-trained occupational physician can deliver in a limited amount of time (45 min twice) worker-tailored counselling able to stimulate an increase in the patient's weekly physical activity. Nevertheless, it must be stressed that this intervention was delivered by a single specialised physician with broad experience in workplace-orientated occupational medicine, and that it was based on a carefully designed manual. It was conducted in a healthcare environment with good connections between the second line of care and occupational healthcare. Therefore, it might be that this low cost intervention may not be easily replicated in other settings or countries with the same effects.

The other RCT study is a pragmatic trial conducted in a large forestry company in Finland with 2-year and 4-year follow-ups. Rantonen et al7 (See page 12) conducted a three-armed RCT in 143 workers who screened positive for at least mild back pain and were identified on several other criteria as having symptoms potentially hampering work; about half of them had radiating pain below the knee. These subjects, 80% of whom were blue-collar workers, were randomly allocated to hospital outpatient rehabilitation, a graded activity program or self-care advice. The hospital-based rehabilitation program was an intensive, biopsychosocial and multidisciplinary program lasting 6.5 h per day, 5 days a week for three successive weeks. The graded activity program consisted of progressive back-specific exercises administered in a physiotherapy outpatient clinic in 1 h sessions twice or three times per week over a 12-week period. The third group were given a copy of the Back Book during their initial examination by the occupational physician who underlined the main messages of the booklet. In comparison to self-care advice, the two active interventions showed some effect on health-related quality of life, pain, disability, pain-related fear and sickness absence. However, the effect on pain was not sustained over the 2-year follow-up, the improvement in health-related quality of life was only achieved after the 1-year follow-up and the reduction in sick leave was minor and not always back specific. In addition, the most intensive and more expensive (hospital-based) intervention did not result in better outcomes than the less intensive intervention in an outpatient clinic.

The strength of this second study lies in its pragmatic approach: each intervention arm was based on existing validated tools or clinical practices and implemented within the usual occupational healthcare of a large company. It was a true prevention trial as the study focused on non-sicklisted employees with relatively mild LBP. The original inclusion criterion of not being sicklisted, however, resulted in low baseline levels of the outcome variables, which in turn could explain the modest effect sizes observed. However, these small effects might also be ascribed to the fact that the intervention did not include any action regarding the workplace environment.

These two studies seem to open up a new field of research by targeting non-sicklisted workers whose low back problems may endanger their ability to continue working. The studies should thus be considered by both researchers and occupational health practitioners who have to promote meaningful, effective and evidence-based prevention policies for LBP. In view of the mixed results of these studies, further research will obviously be needed to define the optimal strategies for secondary prevention of LBP, and the manner in which the workers who can best benefit from them, can be identified.