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1.  The role of physical workload and pain related fear in the development of low back pain in young workers: evidence from the BelCoBack Study; results after one year of follow up 
To study the influence of work related physical and psychosocial factors and individual characteristics on the occurrence of low back pain among young and pain free workers.
The Belgian Cohort Back Study was designed as a prospective cohort study. The study population of this paper consisted of 716 young healthcare or distribution workers without low back pain lasting seven or more consecutive days during the year before inclusion. The median age was 26 years with an interquartile range between 24 and 29 years. At baseline, these workers filled in a questionnaire with physical exposures, work related psychosocial factors and individual characteristics. One year later, the occurrence of low back pain lasting seven or more consecutive days and some of its characteristics were registered by means of a questionnaire. To assess the respective role of predictors at baseline on the occurrence of low back pain in the following year, Cox regression with a constant risk period for all subjects was applied.
After one year of follow up, 12.6% (95% CI 10.1 to 15.0) of the 716 workers had developed low back pain lasting seven or more consecutive days. An increased risk was observed for working with the trunk in a bent and twisted position for more than two hours a day (RR 2.2, 95% CI 1.2 to 4.1), inability to change posture regularly (RR 2.1, 95% CI 1.3 to 3.5), back complaints in the year before inclusion (RR 1.7, 95% CI 1.1 to 2.8), and high scores of pain related fear (RR 1.8, 95% CI 1.0 to 3.1). Work related psychosocial factors and physical factors during leisure time were not predictive.
This study highlighted the importance of physical work factors and revealed the importance of high scores of pain related fear in the development of low back pain among young workers.
PMCID: PMC2078035  PMID: 16361405
low back pain; pain related fear; physical work factors; prospective; young workers
2.  Study protocol title: a prospective cohort study of low back pain 
Few prospective cohort studies of workplace low back pain (LBP) with quantified job physical exposure have been performed. There are few prospective epidemiological studies for LBP occupational risk factors and reported data generally have few adjustments for many personal and psychosocial factors.
A multi-center prospective cohort study has been incepted to quantify risk factors for LBP and potentially develop improved methods for designing and analyzing jobs. Due to the subjectivity of LBP, six measures of LBP are captured: 1) any LBP, 2) LBP ≥ 5/10 pain rating, 3) LBP with medication use, 4) LBP with healthcare provider visits, 5) LBP necessitating modified work duties and 6) LBP with lost work time. Workers have thus far been enrolled from 30 different employment settings in 4 diverse US states and performed widely varying work. At baseline, workers undergo laptop-administered questionnaires, structured interviews, and two standardized physical examinations to ascertain demographics, medical history, psychosocial factors, hobbies and physical activities, and current musculoskeletal disorders. All workers’ jobs are individually measured for physical factors and are videotaped. Workers are followed monthly for the development of low back pain. Changes in jobs necessitate re-measure and re-videotaping of job physical factors. The lifetime cumulative incidence of low back pain will also include those with a past history of low back pain. Incident cases will exclude prevalent cases at baseline. Statistical methods planned include survival analyses and logistic regression.
Data analysis of a prospective cohort study of low back pain is underway and has successfully enrolled over 800 workers to date.
PMCID: PMC3599364  PMID: 23497211
Epidemiology; Ergonomics; Cohort; Low back pain; NIOSH lifting equation
3.  High physical work load and low job satisfaction increase the risk of sickness absence due to low back pain: results of a prospective cohort study 
Objective: To determine whether physical and psychosocial load at work influence sickness absence due to low back pain.
Methods: The research was a part of the study on musculoskeletal disorders, absenteeism, stress, and health (SMASH), a 3 year prospective cohort study on risk factors for musculoskeletal disorders. Workers from 21 companies located throughout The Netherlands participated in the part of this study on sickness absence due to low back pain. The study population consisted of 732 workers with no sickness absences of 3 days or longer due to low back pain in the 3 months before the baseline survey and complete data on the reasons for absences during the follow up period. The mean (range) period of follow up in this group was 37 (7–44) months. Physical load at work was assessed by analyses of video recordings. Baseline information on psychosocial work characteristics was obtained by a questionnaire. Data on sickness absence were collected from company records. The main outcome measure was the rate of sickness absences of 3 days or longer due to low back pain during the follow up period.
Results: After adjustment of the work related physical and psychosocial factors for each other and for other potential determinants, significant rate ratios ranging from 2.0 to 3.2 were found for trunk flexion, trunk rotation, lifting, and low job satisfaction. A dose-response relation was found for trunk flexion, but not for trunk rotation or lifting. Non-significant rate ratios of about 1.4 were found for low supervisor support and low coworker support. Quantitative job demands, conflicting demands, decision authority, and skill discretion showed no relation with sickness absence due to low back pain.
Conclusions: Flexion and rotation of the trunk, lifting, and low job satisfaction are risk factors for sickness absence due to low back pain. Some indications of a relation between low social support, either from supervisors or coworkers, and sickness absence due to low back pain are also present.
PMCID: PMC1740286  PMID: 11983847
4.  Predicting the long term course of low back pain and its consequences for sickness absence and associated work disability 
Low back pain is characterised by a dynamic pattern of episodes and recovery but little is known about the long term course of back pain due to lack of cohort studies with sufficiently long follow up periods.
A cohort of 523 workers in nursing homes and homes for the elderly was followed for two years. Physical load was measured by observations at the workplace. Psychosocial factors at work, individual characteristics, and low back pain were determined by questionnaire once a year. The effect of work load on low back pain and the transition of low back pain into sickness absence was calculated with logistic regression analysis. A Markov model was used to construct a hypothetical cohort of workers with follow up of 40 years (40 cycles of 1 year) with transitional probabilities between no complaints, low back pain, and sickness due to low back pain. Permanent disability was used as end state of health.
The transitional probability from no complaints to low back pain varied between p = 0.25 and p = 0.29, from low back pain to sickness absence between p = 0.09 and p = 0.25, and recurrence of sickness absence varied between p = 0.27 and p = 0.50, depending on the level of physical load. During a 40 year career, total sickness absence due to low back pain was approximately 140 weeks (6.6%) among workers with high physical load and about 30 weeks (1.4%) among those with low physical load.
The Markov approach illustrated the potential impact of physical load on (permanent) disability due to low back pain among workers with exposure to physical load. These consequences may go unnoticed in cohort studies with follow up periods of a few years.
PMCID: PMC2078120  PMID: 16849528
low back pain; Markov model; work disability; sickness absence
5.  The greatest risk for low-back pain among newly educated female health care workers; body weight or physical work load? 
Low back pain (LBP) represents a major socioeconomic burden for the Western societies. Both life-style and work-related factors may cause low back pain. Prospective cohort studies assessing risk factors among individuals without prior history of low back pain are lacking. This aim of this study was to determine risk factors for developing low back pain (LBP) among health care workers.
Prospective cohort study with 2,235 newly educated female health care workers without prior history of LBP. Risk factors and incidence of LBP were assessed at one and two years after graduation.
Multinomial logistic regression analyses adjusted for age, smoking, and psychosocial factors showed that workers with high physical work load had higher risk for developing LBP than workers with low physical work load (OR 1.8; 95% CI 1.1–2.8). In contrast, workers with high BMI were not at a higher risk for developing LBP than workers with a normal BMI.
Preventive initiatives for LBP among health care workers ought to focus on reducing high physical work loads rather than lowering excessive body weight.
PMCID: PMC3404961  PMID: 22672781
Prospective cohort study; Low back pain; Physical work load; Health care work; Musculoskeletal disorders; Body mass index
6.  Cost effectiveness of a multi-stage return to work program for workers on sick leave due to low back pain, design of a population based controlled trial [ISRCTN60233560] 
To describe the design of a population based randomized controlled trial (RCT), including a cost-effectiveness analysis, comparing participative ergonomics interventions between 2–8 weeks of sick leave and Graded Activity after 8 weeks of sick leave with usual care, in occupational back pain management.
An RCT and cost-effectiveness evaluation in employees sick-listed for a period of 2 to 6 weeks due to low back pain. Interventions used are 1. Communication between general practitioner and occupational physician plus Participative Ergonomics protocol performed by an ergonomist. 2. Graded Activity based on cognitive behavioural principles by a physiotherapist. 3. Usual care, provided by an occupational physician according to the Dutch guidelines for the occupational health management of workers with low back pain. The primary outcome measure is return to work. Secondary outcome measures are pain intensity, functional status and general improvement. Intermediate variables are kinesiophobia and pain coping. The cost-effectiveness analysis includes the direct and indirect costs due to low back pain. The outcome measures are assessed before randomization (after 2–6 weeks on sick leave) and 12 weeks, 26 weeks and 52 weeks after first day of sick leave.
The combination of these interventions has been subject of earlier research in Canada. The results of the current RCT will: 1. crossvalidate the Canadian findings in an different sociocultural environment; 2. add to the cost-effectiveness on treatment options for workers in the sub acute phase of low back pain. Results might lead to alterations of existing (inter)national guidelines.
PMCID: PMC317323  PMID: 14629775
Low back pain; Graded Activity; Participative Ergonomics; Return to work; Randomized Controlled Trial; Cost-effectiveness; Occupational health
7.  Threshold of Musculoskeletal Pain Intensity for Increased Risk of Long-Term Sickness Absence among Female Healthcare Workers in Eldercare 
PLoS ONE  2012;7(7):e41287.
Musculoskeletal disorders increase the risk for absenteeism and work disability. However, the threshold when musculoskeletal pain intensity significantly increases the risk of sickness absence among different occupations is unknown. This study estimates the risk for long-term sickness absence (LTSA) from different pain intensities in the low back, neck/shoulder and knees among female healthcare workers in eldercare.
Prospective cohort study among 8,732 Danish female healthcare workers responding to a questionnaire in 2004–2005, and subsequently followed for one year in a national register of social transfer payments (DREAM). Using Cox regression hazard ratio (HR) analysis we modeled risk estimates of pain intensities on a scale from 0–9 (reference 0, where 0 is no pain and 9 is worst imaginable pain) in the low back, neck/shoulders and knees during the last three months for onset of LTSA (receiving sickness absence compensation for at least eight consecutive weeks) during one-year follow-up.
During follow-up, the 12-month prevalence of LTSA was 6.3%. With adjustment for age, BMI, smoking and leisure physical activity, the thresholds of pain intensities significantly increasing risk of LTSA for the low back (HR 1.44 [95%CI 1.07–1.93]), neck/shoulders (HR 1.47 [95%CI 1.10–1.96]) and knees (HR 1.43 [95%CI 1.06–1.93]) were 5, 4 and 3 (scale 0–9), respectively, referencing pain intensity of 0.
The threshold of pain intensity significantly increasing the risk for LTSA among female healthcare workers varies across body regions, with knee pain having the lowest threshold. This knowledge may be used in the prevention of LTSA among health care workers.
PMCID: PMC3401109  PMID: 22911772
8.  Low back pain in Hispanic residential carpenters☆ 
Low back pain (LBP) is a leading cause of lost work time and has been recognized as America's number one workplace safety challenge. Low back pain is occurring at epidemic proportions among construction workers, and minority populations have been underinvestigated for risk of back injury. This project investigated the multiple potential risk factors for occupational LBP among Hispanic residential carpenters.
This investigation evaluated 241 Hispanic residential framing carpenters. Data for this study were collected using a 91-question survey. End points of interest included point, annual, and lifetime prevalence of LBP.
Nineteen percent of respondents reported they had an episode of LBP in their lifetime.
Hispanic residential carpenters reported less than expected prevalence of LBP compared with non-Hispanic counterparts in the same trade and location. Job tasks and personal and workplace risk factors, including psychological and morphological characteristics, affect the prevalence of LBP among Hispanic framing carpenters.
PMCID: PMC2647077  PMID: 19674688
9.  Medical, psychological, and social factors associated with back abnormalities and self reported back pain: a cross sectional study of male employees in a Swedish pulp and paper industry. 
A medical, psychological, and sociological study of 391 male employees in a Swedish pulp and paper industry was performed in 1961. Factors associated with back pain and back abnormality were investigated. Univariate analyses showed associations of back pain with occupational status, low education, duration of employment, low performance on cognitive tests, and neuroticism. Back abnormalities evaluated on the basis of physical examination showed in principle the same associations but the strength as well as the significances were stronger. Multiple logistic regression analyses using data for manual workers showed that neuroticism and duration of employment were directly associated with back pain. The same two variables and low performance on one of the psychological tests were directly associated with back abnormalities. Age showed no direct association with back pain or back abnormalities. Strong associations between back pain and back abnormalities with both perceived health and general working capacity and the doctor's evaluation in the same areas were demonstrated.
PMCID: PMC1007830  PMID: 2954580
10.  Lower back pain in physically demanding college academic programs: a questionnaire based study 
Lower back pain (LBP) is ranked first as a cause of disability and inability to work, and is expected to affect up to 90% of the worlds population at some point in their lifetime. The annual first time incidence of LBP is 5%, and the annual prevalence (i.e. those suffering at time of questioning) is between 15 and 63%. Prospective studies demonstrate that low back problems do not display a six-week spontaneous recovery pattern, as was once believed. The condition is regularly seen to worsen over time, becoming a chronic disorder, influenced by both physical and psychosocial factors.
The current study assessed the level of LBP amongst students engaged in educational programs that were physically demanding, and its influence on lower back problems. A 1-year retrospective questionnaire consisting of 37 closed, open and multi-choice questions was designed to ascertain self-reported information on the occurrence, cause and type of LBP. Treatment, care seeking and general knowledge regarding LBP were also recorded. Students were enrolled in BSc Equine Science, BSc Physical Education and BSc Sports & Exercise Science degree programs and a total number of 188 valid questionnaires were collected.
The self reported, anthropometrical data for participants in this study are: age 20.9 ± 2.7 yrs; height 171.8 ± 9.3 cm; weight 66.7 ± 10.4 kg; female 64% (n = 120), male 36% (n = 68). The overall self reported prevalence of LBP was 32% (n = 61). Within the LBP population, 77% reported their problem as recurring. Two factors showed significance as having an influence on LBP. They were age (21.6 ± 3.5 yrs, p = 0.005) and hours of personal training physical activity (14.0 ± 8.2 hrs per week, p = 0.02). LBP sufferers also displayed poor management of their condition and an interest in education and treatment of their problem.
The current study revealed high prevalence of LBP consistent with that of the literature, and unveiled a recurrence rate and behavioral habits of sufferers, which are warning signs of a more chronic state to come. Novel data presented here offers strong support for the need for prospective injury tracking, plus educational intervention and treatment aimed at prevention of LBP.
PMCID: PMC1950501  PMID: 17631036
11.  Potential Risk Factors of Persistent Low Back Pain Developing from Mild Low Back Pain in Urban Japanese Workers 
PLoS ONE  2014;9(4):e93924.
Study Design
Two-year, prospective cohort data from the Japan epidemiological research of occupation-related back pain study in urban settings were used for this analysis.
To examine the association between aggravated low back pain and psychosocial factors among Japanese workers with mild low back pain.
Summary of Background Data
Although psychosocial factors are strongly indicated as yellow flags of low back pain (LBP) leading to disability, the association between aggravated LBP and psychosocial factors has not been well assessed in Japanese workers.
At baseline, 5,310 participants responded to a self-administered questionnaire including questions about individual characteristics, ergonomic work demands, and work-related psychosocial factors (response rate: 86.5%), with 3,811 respondents completing the 1-year follow-up questionnaire. The target outcome was aggravation of mild LBP into persistent LBP during the follow-up period. Incidence was calculated for the participants with mild LBP during the past year at baseline. Logistic regression was used to explore risk factors associated with persistent LBP.
Of 1,675 participants who had mild LBP during the preceding year, 43 (2.6%) developed persistent LBP during the follow-up year. Multivariate analyses adjusted for individual factors and an ergonomic factor found statistically significant or almost significant associations of the following psychosocial factors with persistent LBP: interpersonal stress at work [adjusted odds ratio (OR): 1.96 and 95% confidence interval (95%CI): 1.00–3.82], job satisfaction (OR: 2.34, 95%CI: 1.21–4.54), depression (OR: 1.92, 95%CI: 1.00–3.69), somatic symptoms (OR: 2.78, 95%CI: 1.44–5.40), support from supervisors (OR: 2.01, 95%CI: 1.05–3.85), previous sick-leave due to LBP (OR: 1.94, 95%CI: 0.98–3.86) and family history of LBP with disability (OR: 1.98, 95%CI: 1.04–3.78).
Psychosocial factors are important risk factors for persistent LBP in urban Japanese workers. It may be necessary to take psychosocial factors into account, along with physical work demands, to reduce LBP related disability.
PMCID: PMC3979726  PMID: 24714616
12.  Development of a risk score for low back pain in office workers - a cross-sectional study 
Low back pain (LBP) is common among office workers and is the most common cause of work-related disability in people under 45 years of age. The aetiology of LBP is widely accepted to be multi-factorial. Prognostic research into office workers at risk of developing LBP has received limited attention. The aims of this study were to develop a risk score to identify office workers likely to have LBP and to evaluate its predictive power.
397 office workers filled out a self-administered questionnaire and underwent physical examination. The questionnaire gathered data on individual, work-related physical and psychosocial data as well as the presence of low back pain in the previous 4 weeks. The physical examination included measurement of body weight, height, waist circumference, hamstrings length, spinal scoliosis, spinal curve, Backache Index and lumbar stability. Logistic regression was used to select significant factors associated with LBP to build a risk score. The coefficients from the logistic regression model were transformed into the components of a risk score.
The model included six items: previous history of working as an office worker, years of work experience, continuous standing for >2 hrs/d, frequency of forward bending during work day, chair having lumbar support and Backache Index outcome. The risk score for LBP in office workers (The Back pain Risk score for Office Workers: The BROW) was built with a risk score ranging from 0 to 9. A cut-off score of ≥4 had a sensitivity of 80% and a specificity of 58%. The positive predictive value and negative predictive values were 70% each.
The BROW is easy and quick to administer. It appears to have reasonable sensitivity, specificity, positive predictive value and negative predictive values for the cut-off point of ≥4. The BROW is a promising tool for use to identify office workers in need of early interventions. Further prospective study is needed to validate the predictive performance of the BROW.
PMCID: PMC3036671  PMID: 21261997
13.  Cumulative Low Back Load at Work as a Risk Factor of Low Back Pain: A Prospective Cohort Study 
Purpose Much research has been performed on physical exposures during work (e.g. lifting, trunk flexion or body vibrations) as risk factors for low back pain (LBP), however results are inconsistent. Information on the effect of doses (e.g. spinal force or low back moments) on LBP may be more reliable but is lacking yet. The aim of the present study was to investigate the prospective relationship of cumulative low back loads (CLBL) with LBP and to compare the association of this mechanical load measure to exposure measures used previously. Methods The current study was part of the Study on Musculoskeletal disorders, Absenteeism and Health (SMASH) study in which 1,745 workers completed questionnaires. Physical load at the workplace was assessed by video-observations and force measurements. These measures were used to calculate CLBL. Furthermore, a 3-year follow-up was conducted to assess the occurrence of LBP. Logistic regressions were performed to assess associations of CLBL and physical risk factors established earlier (i.e. lifting and working in a flexed posture) with LBP. Furthermore, CLBL and the risk factors combined were assessed as predictors in logistic regression analyses to assess the association with LBP. Results Results showed that CLBL is a significant risk factor for LBP (OR: 2.06 (1.32–3.20)). Furthermore, CLBL had a more consistent association with LBP than two of the three risk factors reported earlier. Conclusions From these results it can be concluded that CLBL is a risk factor for the occurrence of LBP, having a more consistent association with LBP compared to most risk factors reported earlier.
PMCID: PMC3563950  PMID: 22718286
Low back loading; Ergonomics; Workers; Longitudinal studies; Observational studies
14.  Prognostic factors for duration of sick leave in patients sick listed with acute low back pain: a systematic review of the literature 
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.
PMCID: PMC1740930  PMID: 16299094
15.  Association between sitting and occupational LBP 
European Spine Journal  2006;16(2):283-298.
Low back pain (LBP) has been identified as one of the most costly disorders among the worldwide working population. Sitting has been associated with risk of developing LBP. The purpose of this literature review is to assemble and describe evidence of research on the association between sitting and the presence of LBP. The systematic literature review was restricted to those occupations that require sitting for more than half of working time and where workers have physical co-exposure factors such as whole body vibration (WBV) and/or awkward postures. Twenty-five studies were carefully selected and critically reviewed, and a model was developed to describe the relationships between these factors. Sitting alone was not associated with the risk of developing LBP. However, when the co-exposure factors of WBV and awkward postures were added to the analysis, the risk of LBP increased fourfold. The occupational group that showed the strongest association with LBP was Helicopter Pilots (OR=9.0, 90% CI 4.9–16.4). For all studied occupations, the odds ratio (OR) increased when WBV and/or awkward postures were analyzed as co-exposure factors. WBV while sitting was also independently associated with non-specific LBP and sciatica. Vibration dose, as well as vibration magnitude and duration of exposure, were associated with LBP in all occupations. Exposure duration was associated with LBP to a greater extent than vibration magnitude. However, for the presence of sciatica, this difference was not found. Awkward posture was also independently associated with the presence of LBP and/or sciatica. The risk effect of prolonged sitting increased significantly when the factors of WBV and awkward postures were combined. Sitting by itself does not increase the risk of LBP. However, sitting for more than half a workday, in combination with WBV and/or awkward postures, does increase the likelihood of having LBP and/or sciatica, and it is the combination of those risk factors, which leads to the greatest increase in LBP.
PMCID: PMC2200681  PMID: 16736200
Sitting; LBP; Sciatica; Epidemiology; Review
16.  Using a psychosocial subgroup assignment to predict sickness absence in a working population with neck and back pain 
The overall objective was to evaluate the predictive validity of a subgroup classification based on the Swedish version of the MPI, the MPI-S, among gainfully employed workers with neck pain (NP) and/or low back pain (LBP) during a follow-up period of 18 and 36 months.
This is a prospective cohort study that is part of a larger longitudinal multi-centre study entitled Work and Health in the Process and Engineering Industries (AHA). The attempt was to classify individuals at risk for developing chronic disabling NP and LBP. This is the first study using the MPI-questionnaire in a working population with NP and LBP.
Dysfunctional individuals (DYS) demonstrated more statistically significant sickness absence compared to adaptive copers (AC) after 36 months. DYS also had a threefold increase in the risk ratio of long-term sickness absence at 18 months. Interpersonally distressed (ID) subgroup showed overall more sickness absence compared to the AC subgroup at the 36-month follow-up and had a twofold increase in the risk ratio of long-term sickness absence at 18 months. There was a significant difference in bodily pain, mental and physical health for ID and DYS subgroups compared to the AC group at both follow-ups.
The present study shows that this multidimensional approach to the classification of individuals based on psychological and psychosocial characteristics can distinguish different groups in gainfully employed working population with NP/LBP. The results in this study confirm the predictive validity of the MPI-S subgroup classification system.
PMCID: PMC3097013  PMID: 21521502
17.  Comparison of two different approaches for the analysis of data from a prospective cohort study: an application to work related risk factors for low back pain 
Aims: To compare the results of a traditional approach using standard regression for the analysis of data from a prospective cohort study with the results of generalised estimating equations (GEE) analysis.
Methods: The research was part of a three year prospective cohort study on work related risk factors for low back pain. The study population consisted of a cohort of 1192 workers with no low back pain at baseline. Information on work related physical and psychosocial factors and the occurrence of low back pain was obtained by means of questionnaires at baseline and at the three annual follow up measurements. In a traditional standard logistic regression model, physical and psychosocial risk factors at baseline were related to the cumulative incidence of low back pain during the three year follow up period. In a GEE logistic model, repeated measurements of the physical and psychosocial risk factors were related to low back pain reported at one measurement point later.
Results: The traditional standard regression model showed a significant effect of flexion and/or rotation of the upper part of the body (OR = 1.8; 95% CI: 1.2 to 3.0), but not of moving heavy loads (OR = 1.4; 95% CI: 0.7 to 3.1). The GEE model showed a significant effect of both flexion and/or rotation of the upper part of the body (OR = 2.2; 95% CI: 1.5 to 3.3) and moving heavy loads (OR = 1.5; 95% CI: 1.0 to 2.4). No significant associations with low back pain were found for the psychosocial work characteristics with either method, but the GEE model showed weaker odds ratios for these variables than the traditional standard regression model.
Conclusions: Results show that there are differences between the two analytical approaches in both the magnitude and the precision of the observed odds ratios.
PMCID: PMC1740320  PMID: 12107294
18.  Low back pain around retirement age and physical occupational exposure during working life 
BMC Public Health  2011;11:268.
Physical occupational exposure is a risk factor for low back pain in workers but the long term effects of exposure remain unclear. As several countries consider increasing the retirement age, further information on this topic is relevant. This study aimed to describe the prevalence of low back pain among middle aged and aging individuals in the general French population according to physical occupational exposure and retirement status.
The study population originated from the French national survey 'Enquête décennale santé 2002'. Low back pain for more than 30 days within the previous twelve months (LBP) was assessed using a French version of the Nordic questionnaire. Occupational exposure was self assessed. Subjects were classified as "exposed" if they were currently or had previously been exposed to handling of heavy loads and/or to tiring postures. The weighted prevalence of LBP was computed separately for men and women, for active (aged 45-59) and retiree (aged 55-74), according to 5-year age group and past/present occupational exposure.
For active men, the prevalence of LBP was significantly higher in those currently or previously exposed (n = 1051) compared with those never exposed (n = 1183), respectively over 20% versus less than 11%. Among retired men, the prevalence of LBP tended towards equivalence with increasing age among those previously exposed (n = 748) and those unexposed (n = 599).
Patterns were quite similar for women with a higher prevalence in exposed active women (n = 741) compared to unexposed (n = 1260): around 25% versus 15%. Similarly, differences between previously exposed (n = 430) and unexposed (n = 489) retired women tended to reduce with age.
The prevalence of LBP in active workers was associated with occupational exposure. The link with past exposure among retirees decreased with age. These results should be considered for policies dealing with prevention at the workplace and retirement.
PMCID: PMC3103456  PMID: 21526996
19.  The effect of insoles on the incidence and severity of low back pain among workers whose job involves long-distance walking 
European Spine Journal  2005;14(6):546-550.
The prevalence and incidence of low back pain in general society is high. Workers whose job involves walking long distances have an even higher tendency to suffer from low back pain. A positive effect of insoles in reducing low back pain was found in professional sports players. This was not examined on people whose job involves walking long distances. In this double blind prospective study we examined the effectiveness of insoles constructed in a computerized method to placebo insoles in 58 employees whose work entailed extensive walking and who suffered from low back pain. The evaluation was performed by the MILLION questionnaire, which is considered as a valid questionnaire for evaluation of low back pain. We calculated the differences of the pain intensity before and after the intervention, in the employees using the insoles manufactured by computer in comparison to the users of the placebo insoles. In each group, the analysis was performed in comparison to the baseline. A total of 81% of the employees preferred the real insoles as effective and comfortable in comparison to 19% of the users of the placebo insoles (P<0.05). The results of this study indicate a substantial improvement in the low back pain after the use of the true insoles. The average pain intensity according to the MILLION questionnaire before the use of the insoles was 5.46. However, after the use of the real insoles and the placebo insoles, the average pain intensity decreased to 3.96 and 5.11, respectively. The difference of the average pain intensity at the start of the study and after the use of the real insoles was significant: −1.49 (P=0.0001), whereas this difference after the use of the placebo insoles was not significant: −0.31 (P=0.1189). The reported severity of pain also decreased significantly: a level 5 pain and above was reported by 77% of the subjects at the start of the study. After the use of the real insoles only 37.9% of the subjects reported a similar degree of pain severity, and 50% of the subjects did so after the use of the placebo insoles (P< 0.05). We did not find a link between low back pain and other variables such as gender, age, number of offspring, work seniority, smoking, previous use of insoles and previous medication. This study demonstrates that the low back pain decreased significantly after the use of real insoles compared to placebo ones.
PMCID: PMC3489231  PMID: 15668775
Low back pain; Workers; Insoles; Long distance walking
20.  Estimating investment worthiness of an ergonomic intervention for preventing low back pain from a firm's perspective 
Applied ergonomics  2008;40(3):457-463.
A mathematical model was developed for estimating the net present value (NPV) of the cash flow resulting from an investment in an intervention to prevent occupational low back pain (LBP). It combines biomechanics, epidemiology, and finance to give an integrated tool for a firm to use to estimate the investment worthiness of an intervention based on a biomechanical analysis of working postures and hand loads. The model can be used by an ergonomist to estimate the investment worthiness of a proposed intervention. The analysis would begin with a biomechanical evaluation of the current job design and post-intervention job. Economic factors such as hourly labor cost, overhead, workers' compensation costs of LBP claims, and discount rate are combined with the biomechanical analysis to estimate the investment worthiness of the proposed intervention. While this model is limited to low back pain, the simulation framework could be applied to other musculoskeletal disorders. The model uses Monte Carlo simulation to compute the statistical distribution of NPV, and it uses a discrete event simulation paradigm based on four states: (1) working and no history of lost time due to LBP, (2) working and history of lost time due to LBP, (3) lost time due to LBP, and (4) leave job. Probabilities of transitions are based on an extensive review of the epidemiologic review of the low back pain literature. An example is presented.
PMCID: PMC2765332  PMID: 19028380
spine; cost-benefit; investment; intervention
21.  Low back pain predict sickness absence among power plant workers 
Low back pain (LBP) remains the predominant occupational health problem in most industrialized countries and low-income countries. Both work characteristics and individual factors have been identified as risk factors. More knowledge about the predictors of sickness absence from LBP in the industry will be valuable in determining strategies for prevention.
The aim of this longitudinal study was to investigate whether individual, work-related physical risk factors were involved in the occurrence of LBP sickness absence.
A follow-up study was conducted among 489 workers, aged 18–65 years, at Kosovo Energetic Corporation in Kosovo. This cross-sectional study used a self-administered questionnaire to collect data on individual and work-related risk factors and the occurrence of LBP sickness absence. Logistic regression models were used to determine associations between risk factors and the occurrence of sickness absence due to LBP.
Individual factors did not influence sickness absence, whereas work-related physical factors showed strong associations with sickness absence. The main risk factors for sickness absence due to LBP among production workers were extreme trunk flexion (OR = 1.71, 95% CI = 1.05–2.78) as well as very extreme trunk flexion (OR = 6.04, 95% CI = 1.12–32.49) and exposure to whole-body vibration (OR = 1.75, 95% CI = 1.04–2.95).
Reducing sickness absence from LBP among power plant workers requires focusing on the working conditions of blue-collar workers and risk factors for LBP. Increasing social support in the work environment may have effects in reducing sickness absence from LBP.
PMCID: PMC2992865  PMID: 21120081
Low back pain; occupational; physical risk factors; sick leave
22.  The effectiveness of graded activity for low back pain in occupational healthcare 
Low back pain is a common medical and social problem associated with disability and absence from work. Knowledge on effective return to work (RTW) interventions is scarce.
To determine the effectiveness of graded activity as part of a multistage RTW programme.
Randomised controlled trial.
Occupational healthcare.
112 workers absent from work for more than eight weeks due to low back pain were randomised to either graded activity (n = 55) or usual care (n = 57).
Graded activity, a physical exercise programme aimed at RTW based on operant‐conditioning behavioural principles.
Main outcome measures
The number of days off work until first RTW for more then 28 days, total number of days on sick leave during follow up, functional status, and severity of pain. Follow up was 26 weeks.
Graded activity prolonged RTW. Median time until RTW was equal to the total number of days on sick leave and was 139 (IQR = 69) days in the graded activity group and 111 (IQR = 76) days in the usual care group (hazard ratio = 0.52, 95% CI 0.32 to 0.86). An interaction between a prior workplace intervention and graded activity, together with a delay in the start of the graded activity intervention, explained most of the delay in RTW (hazard ratio = 0.86, 95% CI 0.40 to 1.84 without prior intervention and 0.39, 95% CI 0.19 to 0.81 with prior intervention). Graded activity did not improve pain or functional status clinically significantly.
Graded activity was not effective for any of the outcome measures. Different interventions combined can lead to a delay in RTW. Delay in referral to graded activity delays RTW. In implementing graded activity special attention should be paid to the structure and process of care.
PMCID: PMC2077992  PMID: 16847036
low back pain; graded activity; randomised controlled trial; effectiveness; cognitive behavioural; return‐to‐work
23.  Low Back Pain in Underground Gold Miners in Ghana 
Ghana Medical Journal  2007;41(1):21-25.
Biomechanical lumbo-spinal strain and intense physical work are the characteristic hallmarks of mining work.
To determine the prevalence and predisposing factors for Low Back Pain (LBP) among male underground gold miners at the Obuasi gold mine in Ghana.
This is a cross sectional study on 280 male underground gold miners from June to October 2001 with a structured questionnaire administered through interviews.
The twelve months prevalence of low back pain among miners was 67%. The mean age of the workers was 40 years (± 5.6, ranging from 27 to 53 years). Increasing age was significantly associated with low back pain, (P=0.05) OR 2.07 (95% CI 0.99 to 4.34) after adjustment for smoking and occupation. Prevalence of LBP was highest among workers performing engineering (82%) duties. Heavy physical work (77%), was identified as a major cause of LBP, which could be prevented by the use of lifting aids (16%).
The prevalence of low back pain in this group is comparable with that obtained from other studies in Africa and Europe. Training and education as a means of reducing LBP was suggested by just a few of the respondents.
PMCID: PMC1890537  PMID: 17622335
Low Back Pain; prevalence; gold miners; occupation; cross-sectional
24.  Working hours spent on repeated activities and prevalence of back pain 
Background and Aims: Back pain is the most common reason for filing workers' compensation claims in the United States and affects large numbers of workers in many other countries. To evaluate the associations between working hours spent on repeated activities and back pain, data gathered through the 1988 National Health Interview Survey were analysed. The data were also used to identify high risk occupations.
Methods: A total of 30 074 workers participated in the survey. They were asked to provide information on their job, including the time spent on repeated strenuous physical activities (RSPA) and the time spent on repeated bending, twisting, or reaching (RBTR) on a typical job. A case of back pain was defined as a worker who had back pain every day for a week or more during the past 12 months. Each case was asked to report the cause of back pain. Those who attributed their back pain to repeated activities (RA) or a single accident or injury (AI) were asked to recall whether they performed RA or had the AI at work.
Results: Whereas the prevalence of back pain increased as the number of working hours spent on RSPA or RBTR increased, the dose–response relations were not linear for either factor, suggesting the involvement of other unmeasured factors. The estimated overall prevalence of RA back pain was 8.9% among male workers and 5.9% among female workers. "Carpenters" had the highest prevalence (19.2%) and most cases (338 000) among the major occupations of men, and "nursing aides, orderlies, and attendants" had the highest prevalence (15.2%) and most cases (217 000) among the major occupations of women.
Conclusions: The number of hours spent on repeated activities at work was associated with the prevalence of back pain. This study identified high risk occupations for future research and intervention.
PMCID: PMC1740219  PMID: 12356929
25.  A screening questionnaire to predict no return to work within 3 months for low back pain claimants 
European Spine Journal  2008;17(3):380-385.
The objective of the present study was to develop a short prediction questionnaire for estimating the risk of no return to work (RTW) within 3 months of sick leave to facilitate triage and management of a patient population of subacute low-back pain (LBP) sufferers. We conducted a prospective study with a 3-month follow-up on 186 patients with LBP introducing a claim for sickness benefits to the largest sickness fund in Belgium. Patients completed a screening questionnaire within 2 weeks after claim submission. All patients were invited for clinical assessment, at 6–8 weeks of sick leave, by the medical adviser. Patients’ work status was recorded by the sickness fund. About 20% of the patients did not resume work at 3 months’ sick leave. They were more likely to experience pain below the knee, to have an own previous prediction of a 100% no RTW and to have a severe interference of pain on daily activities. The screening tool based on these three items correctly classified 73.7% of the non-resumers and 78.4% of the resumers at a cut-off score of 0.22. The findings of this study provide evidence of the utility of a short screening questionnaire for future use in intervention studies in a social security setting.
PMCID: PMC2270393  PMID: 18172698
Low back pain; Return to work; Screening; Predictors; Outcomes

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