Risk factors for sickness absence because of low back pain among scaffolders: a 3-year follow-up study

Assessing the Feasibility of EMG Biofeedback to Reduce the Upper Trapezius Muscle Excitation during a Seated Row Exercise, a Non-randomized Comparative Study

The upper trapezius muscle is often excessively excited during resistance training exercises, increasing the shoulder's liability to musculoskeletal disorders of individuals participating in overhead sports or throwing activities. Different approaches have been proposed for reducing the potentially harmful loading of the upper trapezius. None, however, has been devised to deal directly with the main culprit: the muscle excitation. This non-randomized comparative study explores the feasibility of biofeedback based on surface electromyograms (EMGs) in suppressing undue excitation of the upper trapezius during a seated row exercise. Eight male volunteers were instructed to perform the wide-grip seated row exercise without and with the EMG biofeedback of the upper trapezius. Surface EMGs from the three portions of the trapezius and the serratus anterior were sampled with pairs of surface electrodes. A triaxial accelerometer was positioned on the weight stack for the identification of the exercise phase and repetition. This study showed that during the "with biofeedback" condition, the participants were able to activate the upper trapezius and serratus anterior to a lower degree (~ 10%) compared to the "without biofeedback" condition. Future studies should explore if this can lead to greater gains in muscle performance and/or reduce the risk of shoulder injury.

A Lower-Back Exoskeleton with a Four-bar Linkage Structure for Providing Extensor Moment and Lumbar Traction Force

Lower back pain and related injuries are prevalent and serious problems in various industries, and high compression force to the lumbosacral (L5/S1) region has been known as one of the key factors. Previous research on passive lower back exoskeletons focused on reducing lumbar muscle activation by providing an extensor moment. Additionally, lumbar traction forces can reduce the compression force, and is a common treatment method for lower back pain in clinics. In this paper, we propose a novel passive lower back exoskeleton that provides both extensor moment and lumbar traction force. The working principle of the exoskeleton, extending the coil springs during lumbar flexion, and its design criteria regarding the amount of each force element were provided. The kinematic model explained its operation, and the dynamic simulation estimated its performance and validated its satisfaction with the design criteria. The biomechanical model provided a brief insight into the expected exoskeleton's effect on the reduced lower back compression force. Ten subjects performed static holding and dynamic lifting tasks, and the generated force elements in two directions, parallel and perpendicular to the trunk, were evaluated using a force sensor and electromyography sensors, respectively. The experiment demonstrated a pulling force opposite to the direction of intradiscal pressure and reduced erector spinae activation. This implies the effect of wearing the exoskeleton to decrease the intervertebral pressure during static back bending or heavy lifting tasks.

Changes in the distribution of muscle activity when using a passive trunk exoskeleton depend on the type of working task: A high-density surface EMG study

Exoskeleton effectiveness in reducing muscle efforts has been usually assessed from surface electromyograms (EMGs) collected locally. It has been demonstrated, however, muscle activity redistributes within the low back muscles during static and dynamic contractions, suggesting the need of detecting surface EMGs from a large muscle region to reliably investigate changes in global muscle activation. This study used high-density surface EMG to assess the effects of a passive trunk exoskeleton on the distribution of low back muscles' activity during different working tasks. Ten, male volunteers performed a static and a dynamic task with and without the exoskeleton. Multiple EMGs were sampled bilaterally from the lumbar erector spinae muscles while the hip and knee angles were measured unilaterally. Key results revealed for the static task exoskeleton led to a decrease in the average root mean square (RMS) amplitude (∼10%) concomitantly with a stable mean frequency and a redistribution of muscle activity (∼0.5 cm) in the caudal direction toward the end of the task. For the dynamic task, the exoskeleton reduced the RMS amplitude (∼5%) at the beginning of the task and the variability in the muscle activity distribution during the task. Moreover, a reduced range of motion in the lower limb was observed when using the exoskeleton during the dynamic task. Current results support the notion the passive exoskeleton has the potential to alleviate muscular loading at low back level especially for the static task.

Investigating the effect of a passive trunk exoskeleton on local discomfort, perceived effort and spatial distribution of back muscles activity

This study aimed at determining the effect of a passive exoskeleton on local perceived discomfort, perceived effort and low back muscles' activity. Thirteen volunteers performed two simulated working tasks with and without the exoskeleton. In the static task, the exoskeleton decreased the lumbar perceived discomfort, the perceived effort and the level of low back muscles' activity (∼10%) while increasing discomfort in the chest and feet. The percent decrease in EMG amplitude was correlated with the percent increase in perceived effort with exoskeleton. For the dynamic task, the exoskeleton increased the discomfort in the chest and decreased the level of back muscle activity (∼5%). Current findings suggest exoskeleton is effective in reducing the back load while increasing the perceived discomfort at non-targeted body regions in both working tasks. The concurrent increase of discomfort in non-targeted areas probably led to a higher perceived effort despite the reduction of low back muscle activity. Practitioner summary: This study provided insights into exoskeleton effects on local discomfort, perceived effort and muscle activity. Overall, the potential benefits of passive exoskeleton should be considered alongside its adverse effects on the non-targeted body regions that can lead to an increase of perceived effort despite the reduction of back muscle activity.

Technically measured compositional physical work demands and prospective register-based sickness absence (PODESA): a study protocol

BACKGROUND

Various physical work demands are shown to be associated with sickness absence. However, these studies have: (a) predominantly used self-reported data on physical work demands that have been shown to be inaccurate compared with technical measurements, (b) principally focused on various physical work demands in 'isolation', i.e. ignoring their co-dependency - compositional nature -, and (c) mainly used register data on long-term sickness absence. The present article describes the protocol of a study with the objective of investigating the association between technically measured compositional data on physical work demands and prospective long- and short-term register-based data on sickness absence.

METHODS

'The technically measured compositional Physical wOrk DEmands and prospective association with register-based Sickness Absence study (PODESA)' comprises data from two Danish cohorts (NOMAD and DPhacto) primarily on blue-collar workers. In the PODESA cohort, data on 1108 workers were collected at baseline (between 2011 and 2014). The cohort data comprise, e.g., self-reported information on descriptives, lifestyle, workday, and health, as well as accelerometer-based measurements of physical work demands (physical activity, movements, and postures). These baseline measurements are linked with prospective register-based data on sickness absence for up to four years after baseline. The prospective association between physical work demands and sickness absence will be analysed using a Compositional Data Analysis approach.

DISCUSSION

PODESA provides a unique possibility of unravelling which combinations of physical work demands are associated with prospective sickness absence. PODESA employs technically measured information on physical work demands (taking into account the compositionality of physical work demand data) and prospective sickness absence data. The findings from PODESA can be used to develop strengthened preventive interventions for sickness absence. Results are expected in 2019-2021.

Prevalence of back pain in a group of elite athletes exposed to repetitive overhead activity

Background

The prevalence of back pain in athletes has been investigated in several studies, but there are still under- or uninvestigated sports discipline like sports exposed to repetitive overhead activity. Elite athletes spend much time in training and competition and, because of the nature of their disciplines, subject their bodies to a great deal of mechanical strain, which puts a high level of stress on their musculoskeletal systems. From this it is hypothesized that elite athletes who engage in repetitive overhead motions experience a higher strain on their spine and thus possibly a higher prevalence of back pain compared with an active control group.

Objectives

To examine the prevalence of back pain and the exact location of pain in a cohort of elite athletes with repetitive overhead activity and in a control group of physically active sport students. Additionally, to examine different characteristics of pain, and to evaluate the influence of confounders on back pain.

Methods

A standardized and validated online back pain questionnaire was sent by the German Olympic Sports Confederation to German national and international elite athletes, and a control group of physically active but non-elite sports students.

Results

The final sample comprised 181 elite athletes of the sports disciplines badminton, beach volleyball, handball, tennis and volleyball and 166 physically active controls. In elite athletes, lifetime prevalence of back pain was 85%, 12-month prevalence was 75%, 3-month prevalence was 58% and point prevalence was 38%; for the physically active control group, these prevalences were 81%, 70%, 59% and 43%, respectively. There was no significant group difference in prevalence over all time periods. The lower back was the main location of back pain in elite athletes across all disciplines and in controls; additionally a distinct problem of upper back pain was found among volleyball players.

Conclusion

Despite the high mechanical load inherent in the sport disciplines included in this study, the elite athletes who engaged in repetitive overhead activities did not suffer more from back pain than the physically active controls. This suggests that other mechanisms may be influencing back pain prevalences in a positive way in these athletes. Furthermore, these disciplines may practice preventive factors for back pain that outweigh their detrimental factors. Therefore, we posit that extensive prevention work is already being implemented in these sports and that there are additional individual protection factors in play. More research is required to explore these suppositions, and should include investigations into which preventive training programs are being used. Nevertheless, in volleyball particularly, a focus on stabilization/preventive training should be applied to the upper back and neck.

Risk Factors Linked to Psychological Distress, Productivity Losses, and Sick Leave in Low-Back-Pain Employees: A Three-Year Longitudinal Cohort Study

Background. Low back pain (LBP) is one of the most common health problems worldwide. Purpose. To investigate the link between baseline demographic and occupational, medical, and lifestyle data with following psychological and occupational outcomes in a large sample of employees with LBP over a 3-year period. Study Design. Three-year prospective cohort study. Methods. Italian-speaking employees (N = 4492) with a diagnosis of LBP were included. Screening at Time 1 was done in order to collect information about severity and classification of LBP, demographic, lifestyle, and occupational status data. Psychological distress (PGWBI) and occupational burden were assessed after 3 years. Results. After 3 years, employees with LBP not due to organic causes had an increased risk of psychological distress. Gender appears to be an important variable for following occupational burden. Indeed, being a white-collar man with a LBP without organic causes seems to be a protective factor for following work outcomes, while being a white-collar woman with a LBP not due to organic causes appears to be a risk factor for subsequent sick leave. Moreover, LBP severity affects psychological and occupational outcomes. Conclusion. Our findings have several implications that could be considered in preventive and supportive programs for LBP employees.

Low back pain and physical activity--A 6.5 year follow-up among young adults in their transition from school to working life

BACKGROUND

The association between leisure time physical activity and low back pain in young adults is unclear and is in the need of prospectively obtained evidence. This study examined the course of low back pain and the association between low back pain and leisure time physical activity in a cohort of young adults in their transition from school to working life.

METHODS

Both low back pain and leisure time physical activity was monitored over a 6.5 year period in 420 subjects starting out as students within hairdressing, electrical installation and media/design. The association between physical activity and low back pain was investigated through the follow-up period by using linear mixed models analysis.

RESULTS

Low back pain was significantly influenced by time and overall there was a decreasing trend of low back pain prevalence throughout the follow-up. Analysis showed a weak trend of decreasing low back pain with moderate/high physical activity levels, but this association was not significant.

CONCLUSIONS

Low back pain decreased during follow-up with baseline as reference. Findings in our study did show non-significant trends of reduced low back pain with increased leisure time physical activity. Still, we could not support the theory of moderate/high levels of physical activity acting protective against low back pain in young adults entering working life. Our results, in combination with previous relevant research, cannot support a clear relationship between physical activity and low back pain for young adults. Thus, recommendations regarding effect of physical activity on reducing low back pain for this group are not clear.

[Sick leave benefits for workers in the Brazilian meat and fish industries in 2008]

This study aims to analyze factors associated with sick leave rates among workers in the meat, fish, and seafood industries in Brazil. The study analyzed all sick leave benefits granted by the country's social security system to workers in these industries in 2008. Incidence of sick leave per 10 thousand jobs was stratified by sex, age, diagnosis, job position, State, and nature and length of benefits. The study analyzed 31,913 sick leaves, with an annual incidence of 788.7. Meat processing and packaging showed the highest incidence, and fish and seafood processing and packaging showed the longest mean length of sick leave. Women showed a higher sick leave incidence, while men received longer average sick leaves. Injuries, musculoskeletal disorders, and mental disorders accounted for 67.2% of sick leaves. The most common diagnoses were lower back pain, first-trimester bleeding in pregnancy, and depression. The data suggest poor job protection and adverse working conditions in these industries.

L4-L5 compression and anterior/posterior joint shear forces in cabin attendants during the initial push/pull actions of airplane meal carts

The aim of the present study was to assess the acute low back load of cabin attendants during cart handling and to identify working situations which present the highest strain on the worker. In a setup, 17 cabin attendants (ten females and seven males) pushed, pulled and turned a 20 kg standard meal cart (L: 0.5m × W: 0.3 m × H: 0.92 m) loaded with extra 20 kg and 40 kg, respectively on two different surfaces (carpet and linoleum) and at three floor inclinations (-2°, 0° and +2°). Two force transducers were mounted as handles. Two-dimensional movement analysis was performed and a 4D WATBAK modelling tool was used to calculate the acute L4-L5 load. No working situations created loads greater than the accepted values for single exertions, however compression and anterior/posterior shear forces during pulling and turning were much higher when compared with pushing. There were significant effects of handling the cart on different floor types, at the varying inclinations and with different cart weights. Additionally, when external forces were reduced, the cabin attendants did not decrease push/pull force proportionally and thus the L4-L5 load did not decrease as much as expected.

[Inability to work: analysis of sickness benefits granted in the State of Rondônia]

This is a descriptive epidemiological study aiming to o estimate the prevalence and duration of sickness benefits granted by the Brazilian Social Security Institute, as well as the clinical causes of inability to work among employees in Rondonia in 2008. The prevalence was submitted by 10,000 workers and stratified by sex, age, diagnosis, economic activity, and type and duration of benefits. Men had a higher prevalence and duration of benefits. Social security benefits were found to be 2,5 times more prevalent than accident benefits and both increased with age. Labor accidents were more prevalent in the age group ranging between 50-59 years, and Forestry, construction and manpower leasing: had the highest prevalence. The main diagnostic groups were injuries, musculoskeletal system disorders and digestive diseases. The duration of the sickness benefits was higher among men, =40 years and in the social security category. The economic activity is an important risk factor for Inability to work, and it needs to be further explored in order to improve sickness prevention and reduce the impact on workers' health arising from environmental conditions and working processes.

Psychosocial work stressors as antecedents of musculoskeletal problems: a systematic review and meta-analysis of stability-adjusted longitudinal studies

Although the relationship between psychosocial workplace conditions and musculoskeletal problems has been extensively studied, the causal impact of psychosocial workplace factors in the development of musculoskeletal problems remains unclear. The purpose of the present study was to conduct a systematic review of baseline-adjusted prospective longitudinal studies estimating the lagged effect of psychosocial risk factors on musculoskeletal problems in industrialized work settings. A literature review was conducted by searching the MEDLINE, EMBASE, and PsychINFO databases dated until August 2009. The authors classified studies into categories of psychological work stressors and musculoskeletal problems. Available effect sizes were converted to odds ratios (OR). ORs were then pooled for each stressor-problem relationship using a random-effects model. Additionally, the possibility of publication bias was assessed with the Duval and Tweedie nonparametric "trim and fill" procedure. In total, 50 primary studies fulfilled inclusion criteria. Within these studies at least five effect sizes were available for 23 of the 45 possible psychosocial work stress-musculoskeletal problems relationships, leaving 9 psychosocial variables and four musculoskeletal problem areas for analyses. Of these 23 relationships, pooled OR estimates were positive and significant ranging from 1.15 to 1.66 with the largest pooled OR estimating the relationship between highly monotonous work and lower back pain. The lagged effect of low social support on lower limb problems was the only effect size for which the statistical test for bias was significant. Most psychosocial stressors had small but significant lagged effects on the development of musculoskeletal problems. Thus, organizational interventions to minimize these stressors may be promising in reducing one risk factor for the development of employee musculoskeletal problems.

VIP in construction: systematic development and evaluation of a multifaceted health programme aiming to improve physical activity levels and dietary patterns among construction workers

BACKGROUND

The prevalence of both overweight and musculoskeletal disorders (MSD) in the construction industry is high. Many interventions in the occupational setting aim at the prevention and reduction of these health problems, but it is still unclear how these programmes should be designed. To determine the effectiveness of interventions on these health outcomes randomised controlled trials (RCTs) are needed. The aim of this study is to systematically develop a tailored intervention for prevention and reduction of overweight and MSD among construction workers and to describe the evaluation study regarding its (cost-)effectiveness.

METHODS/DESIGN

The Intervention Mapping (IM) protocol was applied to develop and implement a tailored programme aimed at the prevention and reduction of overweight and MSD. The (cost-) effectiveness of the intervention programme will be evaluated using an RCT. Furthermore, a process evaluation will be conducted. The research population will consist of blue collar workers of a large construction company in the Netherlands.

INTERVENTION

The intervention programme will be aimed at improving (vigorous) physical activity levels and healthy dietary behaviour and will consist of tailored information, face-to-face and telephone counselling, training instruction (a fitness "card" to be used for exercises), and materials designed for the intervention (overview of the company health promoting facilities, waist circumference measuring tape, pedometer, BMI card, calorie guide, recipes, and knowledge test). MAIN STUDY PARAMETERS/ENDPOINTS: The intervention effect on body weight and waist circumference (primary outcome measures), as well as on lifestyle behaviour, MSD, fitness, CVD risk indicators, and work-related outcomes (i.e. productivity, sick leave) (secondary outcome measures) will be assessed.

DISCUSSION

The development of the VIP in construction intervention led to a health programme tailored to the needs of construction workers. This programme, if proven effective, can be directly implemented.

TRIAL REGISTRATION

Netherlands Trial Register (NTR): NTR2095.

Individual participant data meta-analysis of mechanical workplace risk factors and low back pain

OBJECTIVES

We used individual participant data from multiple studies to conduct a comprehensive meta-analysis of mechanical exposures in the workplace and low back pain.

METHODS

We conducted a systematic literature search and contacted an author of each study to request their individual participant data. Because outcome definitions and exposure measures were not uniform across studies, we conducted 2 substudies: (1) to identify sets of outcome definitions that could be combined in a meta-analysis and (2) to develop methods to translate mechanical exposure onto a common metric. We used generalized estimating equation regression to analyze the data.

RESULTS

The odds ratios (ORs) for posture exposures ranged from 1.1 to 2.0. Force exposure ORs ranged from 1.4 to 2.1. The magnitudes of the ORs differed according to the definition of low back pain, and heterogeneity was associated with both study-level and individual-level characteristics.

CONCLUSIONS

We found small to moderate ORs for the association of mechanical exposures and low back pain, although the relationships were complex. The presence of individual-level OR modifiers in such an area can be best understood by conducting a meta-analysis of individual participant data.

Risk factors for illness absence due to musculoskeletal disorders in a 4-year prospective study of a petroleum-manufacturing population

OBJECTIVES

To quantify risk factors for nonoccupational absence from musculoskeletal disorders (MSD) among petroleum-manufacturing employees.

METHODS

We conducted a 4-year follow-up study including 860 employees with an MSD illness absence of 4 days or longer and 5691 employees with no MSD absence. Odds ratios were calculated using logistic regression.

RESULTS

Risk of MSD absence from low back and non-low back disorders was significantly associated with physically demanding job, overweight/obesity, prior absence from MSD, and absence from cardiovascular, respiratory, or mental illness, or accidents during the study period. Smoking also increased risk of low back disorders.

CONCLUSIONS

Results suggest it is possible to reduce the impact of MSD through integrated safety prevention and health promotion programs including traditional elements of job factor evaluation, training, and ergonomics, but also health counseling and support for weight reduction, smoking cessation, and personal fitness programs.

Physical activity and low back pain: a systematic review of recent literature

The objective of the study is to systematically evaluate the available evidence on the association between physical activity (i.e. occupational load and non-occupational physical activities) and low back pain (LBP). A systematic approach was used to explore the literature between 1999 and 2009. Studies were selected for inclusion following a comprehensive search of Medline, Embase and CINAHL. The methodological quality of each study was assessed. Studies were considered to be of 'high quality' if they met the cut-off criterion of 60% of the maximum available quality score. Thirty-six cohort or case-control studies were retrieved. Heavy workload and the accumulation of loads or frequency of lifts were moderate to strong risk factors for LBP. Strong associations were found for flexed, rotated and the awkward positions of the lumbar spine. Inconsistent results were found for leisure time physical activities, sports and physical exercise. Studies focusing on daily habitual physical activities (e.g. domestic activities and commuting) in association with LBP are lacking. In conclusion, the occurrence of LBP is related to the nature and intensity of the physical activities undertaken. However, physical activities can be subdivided into separate types and intensities and the ultimate physical load is the sum of all these activities. This makes it difficult to designate one particular activity as the cause of LBP.

Correlating the anatomical site of injury and work-related factors with sick leave duration following minor musculoskeletal injuries

Many factors are associated with long sick leaves and therefore, reliance solely on disease-related factors can potentially underestimate sick leave durations. Here, we wanted to assess the association between the injury sites, work-related factors, and the length of sick leaves. Comprehensive medical legal reports of workers with pure minor musculoskeletal injuries were reviewed. 2029 reports of workers were included. 32.8% had sick leaves of less than a week in duration. Lower limb injuries were associated with longer sick leaves only in patients performing strenuous jobs. Public sector workers sustaining an injury at work and performing strenuous jobs were associated with longer sick leaves. Senior workers returned earlier to work, but age and gender were not strongly correlated with long sick leaves. There was a weak but significant association between sick leave duration and the period spent refraining from hobby activities, and almost all patients returned to their work before their hobbies.

Causal assessment of workplace manual handling or assisting patients and low back pain: results of a systematic review

BACKGROUND CONTEXT

Low back pain (LBP) is a common musculoskeletal disorder associated with a considerable social and economic burden within the working-age population. Despite an unclear etiology, numerous physical activities are suspected of leading to LBP. Declaring a causal relationship between occupational activities and LBP remains challenging and requires a methodologically rigorous approach.

PURPOSE

To conduct a systematic review focused on assessing the potentially causal relationship between workplace manual handling or assisting patients and LBP.

STUDY DESIGN

Systematic review of the literature.

SAMPLES

Studies reporting an association between workplace manual handling or assisting patients and LBP.

OUTCOME MEASURES

Numerical association between different levels of exposure to manual handling or assisting patients, and the presence or severity of LBP.

METHODS

A systematic review was conducted using Medline, EMBASE, CINAHL, Cochrane Library, and Occupational Safety and Health database, gray literature, hand-searching occupational health journals, reference lists of included studies, and content experts. The methodological quality of each study was assessed using a modified Newcastle-Ottawa Scale (NOS) for observational studies. The overall level of evidence supporting various Bradford-Hill criteria for causality for each category of manual handling or assisting patients and type of LBP was then evaluated. Studies were deemed of higher quality if they received a score of five or more on the modified NOS and used appropriate statistical analysis methods.

RESULTS

This search yielded 2,766 citations, and 32 studies met the eligibility criteria. Three high-quality studies reported on manual handling and LBP, including two prospective cohorts and one cross-sectional design. None demonstrated a significant association in most of their multivariate risk estimates. One study was able to assess dose-response and temporality, but its results did not support these criteria. Only one study discussed the biological plausibility of this association. Four high-quality studies evaluated assisting patients and LBP, including two case-controls, one cross-sectional, and one prospective cohort design. These studies were consistent in reporting no significant association. Two studies demonstrated a nonsignificant dose-response trend, and two studies discussed the biological plausibility of this association. No studies were able to demonstrate the temporality or experiment criteria.

CONCLUSIONS

The studies reviewed did not support a causal association between workplace manual handling or assisting patients and LBP in a Bradford-Hill framework. Conflicting evidence in specific subcategories of assisting patients was identified, suggesting that tasks such as assisting patients with ambulation may possibly contribute to LBP. It appears unlikely that workplace manual handling or assisting patients is independently causative of LBP in the populations of workers studied.

Causal assessment of awkward occupational postures and low back pain: results of a systematic review

BACKGROUND CONTEXT

Low back pain (LBP) is a prevalent and costly musculoskeletal disorder that often occurs in the working-age population. Although numerous physical activities have been implicated in its complex etiology, determining causation remains challenging and requires a methodologically rigorous approach.

PURPOSE

To conduct a systematic review of the scientific literature focused on establishing a causal relationship between awkward occupational postures and LBP.

STUDY DESIGN

Systematic review of the literature using MEDLINE, EMBASE, CINAHL, Cochrane Library, and Occupational Safety and Health database, gray literature, hand-searching occupational health journals, reference lists of included studies, and experts. Evaluation of methodological quality using a modified Newcastle-Ottawa Scale for observational studies. Summary levels of evidence for each of the Bradford Hill criteria for causality for each category of awkward occupational posture and type of LBP.

SAMPLE

Studies reporting an association between awkward occupational postures and LBP.

OUTCOME MEASURES

Numerical association between different levels of exposure to awkward occupational postures and the presence or severity of LBP.

METHODS

A systematic review was performed to identify, evaluate, and summarize the literature related to establishing a causal relationship, according to Bradford Hill criteria, between awkward occupational postures and LBP.

RESULTS

This search yielded 2,766 citations. Eight high-quality studies reported on awkward occupational postures and LBP. Three were case-control studies, one was cross-sectional, and four were prospective cohort studies. There was strong evidence for consistency of no association between awkward occupational postures and LBP, with only two studies demonstrating significant associations in most of their risk estimates compared with six studies reported mainly nonsignificant associations. Two studies assessed dose response, with one study demonstrating a nonsignificant dose-response trend. Three studies were able to assess temporality, but all demonstrated nonsignificant risk estimates. Biological plausibility was discussed by two studies. There was no available evidence to assess the experiment criterion for causality.

CONCLUSIONS

There was strong evidence from six high-quality studies that there was no association between awkward postures and LBP. Similarly, there was strong evidence from three high-quality studies that there was no temporal relationship. Moreover, subgroup analyses identified only a handful of studies that demonstrated only weak associations and no evidence for other aspects of causality in certain specific subcategories. It is therefore unlikely that awkward occupational postures are independently causative of LBP in the populations of workers studied.

Estimating investment worthiness of an ergonomic intervention for preventing low back pain from a firm's perspective

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.

Place of residence as a correlate of sickness absence in Sweden

A postal questionnaire was sent to 1500 randomly selected men and women aged 20-64 years living in three sparsely populated municipalities in northern Sweden with high rates of sickness absence, and to 1000 corresponding inhabitants in the Swedish capital Stockholm with a low rate of sickness absence. The proportion of participants aged >or=45 years was higher and incomes were lower in municipalities with high rates of sickness absence. In multiple logistic regression analyses with age, education, income, somatic health, mental health, pain and place of residence as independent variables, significant correlates of sick listing in men were: age >or=45 years (odds ratio 5.0; 95% confidence interval 2.4-10.3), poor somatic health (5.4; 2.6-11.0) and severe musculoskeletal pain (4.7; 2.4-9.1); and in women: age >or=45 years (2.6; 1.5-4.8), poor somatic health (12.2; 6.1-24.4), poor mental health (4.5; 2.0-10.1) and severe musculoskeletal pain (5.4; 2.7-10.5). Mental health was deleted by the logistic model for men, and income, education and place of residence for both sexes. We conclude that no support was found for the assumption that factors attributable to place of residence could explain the regional differences in sickness absence.

Reduced work capacity after lumbar disc surgery: The role of cognitive-behavioral and work-related risk factors

A significant number of patients who have had surgery for lumbosacral radicular syndrome still have a reduced work capacity several months later. In a prospective cohort study of 182 people who underwent lumbar disc surgery, we determined the predictive value of preoperatively measured cognitive-behavioral and work-related factors on work capacity 6 months after surgery. Logistic regression analyses indicated that these factors independently predicted work capacity 6 months after surgery. Specifically, fear of movement/(re)injury, more passive pain coping, and higher physical work-load predicted reduced work capacity in multiple logistic regression analyses, taking into account the role of a wide range of control variables including demographic variables, preoperative disability and pain intensity, neurological deficits, intake of analgesics, duration of complaints, and pain intensity 3 days postoperatively. The study supports the need to develop and evaluate preoperative risk screening measures that include both cognitive-behavioral and work-related factors and to evaluate the effectiveness of cognitive-behavioral and work-related interventions in patients at risk of reduced work capacity after surgery for LRS.

Risk factors for new episodes of sick leave due to neck or back pain in a working population. A prospective study with an 18-month and a three-year follow-up

OBJECTIVES

To identify risk factors for new episodes of sick leave due to neck or back pain.

METHODS

This prospective study comprised an industrial population of 2187 employees who were followed up at 18 months and 3 years after a comprehensive baseline measurement. The potential risk factors comprised physical and psychosocial work factors, health-related and pain-related characteristics and lifestyle and demographic factors. The response rate at both follow-ups was close to 73%.

RESULTS

At the 18-month follow-up, 151 participants reported at least one episode of sick-listing due to neck or back pain during the previous year. Risk factors assessed at baseline for sick leave due to neck or back pain at the follow-up were blue-collar work, back pain one or several times during the previous year, 1-99 days of cumulative sickness absence during the previous year (all causes except neck or back pain), uncertainty of one's own working ability in 2 years' time and the experience of few positive challenges at work. After 3 years, 127 participants reported at least one episode of sick leave due to back or neck pain during the year previous to follow-up. The risk factors for this pain-related sick leave were blue-collar work, several earlier episodes of neck pain, no everyday physical activities during leisure time (cleaning, gardening and so on), lower physical functioning and, for blue-collar workers separately, repetitive work procedures.

CONCLUSION

The most consistent risk factors for new episodes of sick leave due to neck or back pain found during both the follow-ups were blue-collar work and several earlier episodes of neck or back pain assessed at baseline. Preventive efforts to decrease sick leave due to neck or back pain may include measures to increase the occurrence of positive challenges at work and to minimise repetitive work procedures. An evidence-based secondary prevention of neck and back pain including advice to stay active is also warranted.

Predicting the long term course of low back pain and its consequences for sickness absence and associated work disability

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

The differential role of pain, work characteristics and pain-related fear in explaining back pain and sick leave in occupational settings

This cross-sectional questionnaire study investigated the role of pain (pain severity, radiating pain), work characteristics (physical workload, job stressors, job satisfaction), negative affect and pain-related fear in accounting for low back pain (LBP) and sick leave (SL) in 1294 employees from 10 companies in Belgium and the Netherlands. An increased risk for short-term LBP (1-30 days during the last year) was observed for workers reporting high physical workload (OR=2.39), high task exertion (OR=1.63) and high negative affect (OR=1.03). For prolonged LBP (>30 days during the last year) severe pain (OR=13.03), radiating pain (OR=2.37) and fear of work-related activities (OR=3.17) were significant risk factors. A lack of decision latitude decreased the risk of long-term LBP (OR=0.39). Short-term SL (1-30 days during the last year) was associated with severe pain (OR=2.83), high physical workload (OR=2.99) and high fear of movement/(re)injury (OR=1.88). A lack of decision latitude increased the risk of short-term SL (OR=1.92). Long-term SL (>30 days during the last year) was associated with radiating pain (OR=3.80) and high fear of movement/(re)injury (OR=6.35). A lack of co-worker support reduced the risk of long-term SL (OR=0.27). These results suggest that physical load factors are relatively more important in the process leading to short-term LBP and short-term SL, whereas job stressors, severe pain, radiation, and pain-related fear are more important in determining the further course and maintenance of the inability to work. The potential implications of these findings for primary and secondary prevention, and occupational rehabilitation are discussed.