Introduction
Low back pain (LBP) causes a lot of misery, is painful for the individual suffering from it, and is costly to employers and society [1]. Various interventions have been tried both to prevent [2] and to treat [3] LBP. Several specific reviews about LBP interventions in the workplace have been published, e.g. ergonomic interventions [4],physical activity [5,6], back belts [6,7] and education [6,8], in addition to occupational health guidelines for the man- agement of LBP at work [9,10]. The aim of this review is to summarize the evidence from a broad spectrum of
workplace interventions trying to prevent and/or treat LBP. LBP is one of the most common subjective health complaints in Western populations [11]. In Britain, the 1 year prevalence was 49% [12] and in the Nordic countries the 1 month prevalence of LBP was 35% [11]. It is also one of the most common causes of sick leave and disability pension in Norway and the Western world [13]. In Norway, 15% of the total amount of sick leave in 1999 was due to LBP [14]. Consequently, the cost for society and the workplace is large and seems to be steadily increasing [1]. Sick leave and costs were chosen as outcome measures due to their importance to organ- izations and society [13]. Since the number of new episodes of LBP and level of pain are important to the individual, these were chosen as additional outcome measures.
Occupational Medicine, Vol. 54 No. 1 © Society of Occupational Medicine 2004; all rights reserved 3
Department of Biological and Medical Psychology, University of Bergen, Norway.
Corresponding author: Torill H. Tveito, Department of Biological and Medical Psychology, University of Bergen, Jonas Liesvei 91, N-5009 Bergen, Norway. Tel: +47 55 58 62 33; fax: +47 55 58 98 72; e-mail: Torill.Tveito@psych.uib.no
Occupational Medicine 2004;54:3–13 DOI: 10.1093/occmed/kqg109
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Because most of the adult population is employed, worksite interventions enable contact with large parts of this population [15]. In addition, musculoskeletal problems are often believed to be work related [16]. Interventions carried out at the workplace will keep employees on sick leave in contact with work and colleagues, which is something believed to make return to work easier [17,18]. However, employees on sick leave with LBP may not benefit from an intervention carried out at the workplace unless they are specifically invited to participate.The prognosis of acute LBP is very good if left to its natural course [19]. After 6 weeks, 90% of cases have recovered and are back at work [13,20,21]. The prognosis deteriorates with the length of the sick leave. Half of the patients treated by primary health care in Norway will not return to work if they have been on sick leave for >8 weeks [22–24]. In recent years, there has been much focus on the importance of psychosocial factors at work for LBP [25]. However, psychosocial factors seem to be most important as LBP progresses to disability, whereas physical factors play a more prominent role in the early stages [26]. In a recent study of occupational factors related to LBP heavy physical workload, low influence over working conditions and poor social relations at work were among the variables most commonly associated with LBP [27]. These findings imply that psychosocial factors are important, but traditional ergonomic factors are not to be forgotten in the process of acknowledging the newer information. The aim of this review was to assess if controlled workplace interventions have a positive effect on LBP, and which interventions are most effective.
Method
Inclusion criteria
Controlled workplace interventions with employees as participants, aiming to prevent or treat LBP were included. One of the following outcome measures had to be used: lost work days or sick leave due to LBP, cost or cost-effectiveness, new episodes of LBP, or level of pain. Studies published in English from 1980 through June 2002 were included. The search was ended in November 2002.
Search strategy
One author searched the databases Medline Advanced, PsycINFO, the ISI base and the Cochrane Controlled Trials Register, and reference lists of relevant publica- tions. The sensitive search strategy used in the Cochrane back reviews [28] was used for searching Medline and
PsycINFO. The search strategy used for the other databases was as close to the sensitive strategy as possible.
Methodological quality assessment
Two of the authors assessed the methodological quality of the studies independently, and later used a consensus method to reach agreement on scoring the articles, with consultation of the third author if disagreement persisted. Using the guidelines of van Tulder et al. [8], the methodological quality of the studies was assessed, and the studies were graded as high, medium or low methodological quality. Blinding of providers and participants was not used as a criterion because of the nature of these interventions. Internal validity was assessed using four criteria: concealment of allocation, withdrawal/drop-out rate, blinded outcome assessment and intention-to-treat analysis [28] (see Table 3). The criteria were rated ‘positive’, ‘unclear’, ‘negative’ or ‘not relevant’. Overall assessment of internal validity was based on a summary of these four criteria. Low risk for bias meant that all criteria were positive, medium risk for bias meant that one or more of the criteria were unclear, and high risk for bias meant that one or more of the criteria were negative.
Evidence assessment
Many studies presented the data in a way not suitable for statistical pooling, and the studies were also heterogeneous regarding study populations, interventions and outcomes. Consequently, we decided not to perform a quantitative meta-analysis, but to summarize the results qualitatively. A qualitative assessment—evidence score— based on design, quality and outcome of the studies was used [29]. The evidence score consisted of four levels: • Strong evidence: evidence from multiple methodo- logically strong studies. • Moderate evidence: evidence from one methodo- logically strong and at least one weak study. • Limited evidence: evidence from one methodologically strong or multiple weak studies. • No evidence: evidence from one methodologically weak study or contradictory outcomes.
Description of the studies
The search in Medline retrieved 60 studies, the search in PsychLIT/PsycINFO added two studies and the search in the Cochrane Controlled Trials Register added 13 studies. Twenty-eight interventions were included in the review, three of them having two publications each, to give a total of 31 publications. Twenty-four studies were preventive interventions, covering 25 publications in total, and four studies were treatment interventions, with six publications in total. The excluded studies either did
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not have a control group, were not workplace inter- ventions or did not use any of the outcome measures. The 24 preventive interventions were split into five subcategories: • educational (10 interventions, 11 publications) • exercise (six interventions) • back belts (five interventions) • multidisciplinary (two interventions) • pamphlet (one intervention) Back schools dominated the preventive interventions in the education subcategory. Back schools were introduced in Sweden in 1970, and the programme involved instruc- tions in proper lifting techniques and body mechanics [30]. Since then, several back schools have been developed, differing in approach, content, length and delivery [30]. Exercise interventions involved specific exercises for strengthening back muscles or for flexibility, or exercises to increase strength and fitness generally. They varied from high to low intensity, were mandatory or voluntary, were performed within or out of working hours, and were of varying duration. Back belts interventions varied in duration and number of subjects, control interventions varied from none to exercise and education. Multi- disciplinary interventions were comprehensive, based on the notion that LBP is multicausal [31]. Interventions aiming to treat employees with LBP were comprehensive, usually combining medical, psychosocial and ergonomic interventions for employees on sick leave with LBP.
Results
For a summary of the results, see Table 1.
Educational interventions
A total of 10 educational interventions were reported in 11 publications, thus being the largest group of inter- ventions [32–42] (see Tables 2 and 3).
Sick leave
The effect of educational interventions on sick leave due to LBP was reported in six studies [32–34,37,39,40].Two studies [32,40] reported a positive effect on sick leave in the intervention group, but there was no significant difference between the intervention and control groups. One study [32] had a risk of selection bias and other methodological weaknesses.The other study [40] was one of the methodologically strongest studies in this group. The rest of the studies did not report significant effects on sick leave. There is no evidence of effect on sick leave from educational interventions.
Costs
In four studies [32,33,39,40], the economic savings to the organizations from educational interventions were assessed. Three studies reported a positive effect; only Daltroy et al. [33] did not find any significant effect on costs. Two studies reported significant effects with important impact for the organizations [32,40]. The study by Brown et al. [32] showed a positive effect from pre- to post-intervention in the intervention group, but the difference between the intervention and control groups was not significant. Selection bias may be a problem in the studies by Brown et al. [32] and Tuchin and Pollard [39]. In the latter, the