Objectives: Physical exposures (e.g., lifting or bending) are believed to be risk factors for low-back pain (LBP), but the literature is inconsistent. Exposure and LBP prevalence differ considerably between occupations, and so exposure-outcome associations could be severely modified by the presence of particular occupational groups. We aimed at investigating the influence of such outlying groups on the properties of associations between exposure and LBP.

Methods: Lifting and trunk flexion were observed for 371 of 1131 workers within 19 groups. LBP was obtained from all workers during three follow-up years. Both exposure variables were associated with LBP (p<0.01) in this parent dataset.

By removing the 19 groups one-by-one and performing logistic regressions analysis on the 18 remaining groups, we demonstrated that one group, mainly road workers, with outlying exposures and LBP prevalence substantially affected the exposure-outcome association in the total population. In order to further examine this phenomenon, we assessed, by simulation, the influence of realistic sizes (n=4, 8, 16, 32, 64, 128), mean exposures (e=2000, 3000, 4000 lifts and e=30, 40, 50% trunk flexion time) and LBP prevalences (p=70, 80, 90, 100%) of the outlying group on the strength and certainty of the eventual relationship between exposure and LBP. For each combination of n, e and p, 3000 virtual studies were constructed, including the simulated group together with the other 18 original groups from the parent data-set. Average OR, OR confidence limits, and power (p<0.05) were calculated across these 3,000 studies as measures of the properties of each virtual study design.

Results: ORs were attenuated more towards 1 and power decreased with smaller values of n, e and p in the outlying group. Changes in group size and prevalence had a larger influence on OR and power than changes in mean exposure.

Conclusions: The size and characteristics of a single group with high exposure and outcome prevalence can strongly influence both the OR point estimate and the likelihood of obtaining significant exposure-outcome associations in studies of large populations. These findings can guide interpretations of prior epidemiological studies and support informed design of future studies.

Objective: Emerging evidence suggests that excessive sitting has negative health effects. However, this evidence largely relies on research using self-reported sitting time, which is known to be biased. To correct this bias, we aimed at developing a calibration model estimating "true" sitting from self-reported sitting.

Methods: Occupational sitting time was estimated by self-reports (the International Physical Activity Questionnaire) and objective measurements (thigh-worn accelerometer) among 99 Swedish office workers at a governmental agency, at baseline and 3 and 12 months afterwards. Following compositional data analysis procedures, both sitting estimates were transformed into isometric log-ratios (ILR). This effectively addresses that times spent in various activities are inherently dependent and can be presented as values of only 0−100%. Linear regression was used to develop a simple calibration model estimating objectively measured "true" sitting ILR (dependent variable) from self-reported sitting ILR (independent variable). Additional self-reported variables were then added to construct a full calibration model. Performance of the models was assessed by root-mean-square (RMS) differences between estimated and objectively measured values. Models developed on baseline data were validated using the follow-up datasets.

Results: Uncalibrated self-reported sitting ILR showed an RMS error of 0.767. Simple and full calibration models (incorporating body mass index, office type, and gender) reduced this error to 0.422 (55%) and 0.398 (52%), respectively. In the validations, model performance decreased to 57%/62% (simple models) and 57%/62% (full models) for the two follow-up data sets, respectively.

Conclusions: Calibration adjusting for errors in self-reported sitting led to substantially more correct estimates of "true" sitting than uncalibrated self-reports. Validation indicated that model performance would change somewhat in new datasets and that full models perform no better than simple models, but calibration remained effective.

Objectives: Many current jobs are characterized by sedentary behaviour (SB) and lack of physical activity (PA). Interventions addressing SB and PA at the workplace may benefit workers’ health. The present review is the first to focus on the effectiveness of interventions implemented during productive work with the intention to change workers’ SB and/or PA while working.

Methods: Scopus was searched for articles published from 1992 until March 12, 2015. Relevant studies were evaluated using the Quality Assessment Tool for Quantitative Studies and summarized in a best-evidence synthesis.

Results: 40 studies describing 41 interventions were included and organized into three categories: alternative workstations (20), interventions promoting stair use (11) and personalized behavioural interventions (10). Strong evidence was found for alternative workstations leading to positive effects on overall SB, while evidence was conflicting for effects on SB and PA at work, overall PA, and work performance. Evidence was moderate for alternative workstations to have no effect on hemodynamics and cardiorespiratory fitness. Stair use promotion interventions were found to increase PA at work, while personalized behavioural interventions increased overall PA; both with moderate evidence. Personalized behavioural interventions were found to have no effect on anthropometric measures (moderate evidence). Regarding work performance and lipid and metabolic profiles, evidence was either conflicting or insufficient.

Conclusions: Current evidence supports that introduction of alternative workstations may have positive effects on overall PA and SB, likely without reducing work performance, while the long-term health effects of all three reviewed categories of interventions remain to be established.

This paper reviews three computer mouse studies in our laboratory where our emphasis was on mechanisms behind computer related disorders. Our approach was sequentially (i) to determine validity of a laboratory model of computer mouse use (painting rectangles) for studying musculoskeletal disorders; to use this model (ii) to study time pressure and precision demands on position sense and muscular oxygenation; and (iii) to determine the effect of pauses (active vs passive) on these parameters. (i) Kinematic data for the painting model showed constrained movements of the wrist similar to CAD work; a support for its validity for a real life situation. (ii) Changes in forearm oxygenation were associated with time pressure and precision demands; a potential for insight into the underlying pathophysiological mechanisms. (iii) Increasing trends in oxygenation and blood volume were associated with pauses, especially active; possible explanation for the alleviating effect of discomfort experienced in real life situations when a pause is implemented.

This systematic review summarizes the evidence on associations between physical and psychosocial work-related exposures and the development of carpal tunnel syndrome (CTS). Relevant databases were searched up to January 2020 for cohort studies reporting associations between work-related physical or psychosocial risk factors and the incidence of CTS. Two independent reviewers selected eligible studies, extracted relevant data, and assessed risk of bias (RoB). We identified fourteen articles for inclusion which reported data from nine cohort studies. Eight reported associations between physical exposure and the incidence of CTS and five reported associations between psychosocial exposures and the incidence of CTS. Quality items were generally rated as unclear or low RoB. Work-related physical exposure factors including high levels of repetition, velocity, and a combination of multiple physical exposures were associated with an increased risk of developing CTS. No other consistent associations were observed for physical or psychosocial exposures at work and CTS incidence.

Objective:  This study systematically summarizes biochemical biomarker research in non-traumatic musculoskeletal disorders (MSDs).  Two research questions guided the review:  1) Are there biochemical markers associated with neck and upper extremity MSDs? and, 2) Are there biochemical markers associated with the severity of neck and upper extremity MSDs? 

Methods:  A literature search was conducted in PubMed and SCOPUS.  Eighty-seven studies met primary inclusion criteria.  Following a quality screen, data were extracted from 44 sufficient quality articles.

Results:  Most of the 87 studies were cross-sectional and utilized convenience samples of patients as both cases and controls.  A response rate was explicitly stated in only 11 (13%) studies.  Less than half of the studies controlled for potential confounding through restriction or in the analysis.  Most sufficient quality studies were conducted in older populations (mean age in one or more analysis group > 50 yrs).

In sufficient quality articles, 82% demonstrated at least one statistically significant association between the MSD(s) and biomarker(s) studied.  Evidence suggested that: a) the collagen repair marker TIMP-1 is decreased in fibroproliferative disorders, b) 5-HT (serotonin) is increased in trapezius myalgia, and c) triglycerides are increased in a variety of MSDs.  Only five studies showed an association between a biochemical marker and MSD severity.

Conclusion: While some MSD biomarkers were identified, limitations in the articles examined included possible selection bias, confounding, spectrum effect (potentially heterogeneous biomarker associations in populations according to symptom severity or duration) and insufficient attention to co-morbid conditions. A list of recommendations for future studies is provided.

Objective Poor cardiorespiratory fitness and health is common among childcare workers. We designed “Goldilocks-games” according to the Goldilocks Work principle to provide high-intensity physical activity for childcare workers. We investigated the effectiveness of this Goldilocks Work intervention in increasing occupational high-intensity physical activity and improving work-related health.

Methods In a two-arm cluster randomized trial, 16 childcare institutions with 142 workers were randomly allocated to either an 8-week Goldilocks Work intervention or a control group. The primary outcome was occupational time in high-intensity physical activity. Secondary outcomes were occupational time in active physical behaviors, heart rate during sleep, pain, physical exhaustion, energy at work, work productivity, and need for recovery. 

Results The intervention was successfully delivered and received. Both groups had a low amount of occupational high-intensity physical activity at baseline, and the intervention group reported playing the games 3.1 (SD 1.5) times/week for a duration of 112.2 (SD 175.0) min/week. However, the intervention did not increase high-intensity physical activity or the secondary outcomes, except for energy at work, measured on a scale from 0-10, increasing 0.65 (95% CI, 0.08-1.21), and need for recovery, measured on a scale from 1-5, decreasing -0.32 (95% CI, -0.54- -0.09).

Conclusion The intervention was successfully delivered and received, but did not increase high-intensity physical activity. The intervention group increased their energy at work and decreased their need for recovery, but not the other health-related outcomes. Research on how to design and implement health-promoting work environment interventions in childcare are needed.

Objectives We aimed at determining the extent to which age, gender, BMI and low back pain (LBP) influence bias in self-reported sedentary behavior and moderate-to-vigorous physical activity (MVPA) among blue-collar workers. 

Methods 147 workers wore an Actigraph accelerometer on the thigh for 2-4 consecutive working days. Proportional time spent sedentary and in MVPA was determined using the Acti4 software. The same variables were also self-reported in a questionnaire. The difference between self-reported and accelerometer-based sedentary time and MVPA was calculated and linearly regressed against age, gender, BMI, and self-reported LBP intensity as main effects, as well as interaction terms combining each of these factors with objectively measured exposure.   

Results Workers objectively spent 64% of their time sedentary and 9% in MVPA. On average, self-reports underestimated sedentary time by 1.5 time percentage points and overestimated MVPA by 5.5%. Workers with mild/no LBP appeared to have the same size of self-report bias in MVPA regardless of how much MVPA they actually had, while workers with high LBP overestimated MVPA to an increasing extent with increasing exposure (interaction: B 0.29, 95%CI 0.05 to 0.53). Age was positively associated with self-report bias in sedentary time (B=0.31, 95%CI=0.09 - 0.54, P=0.008) regardless of actual sedentary time.

Conclusions LBP and age, but not BMI and gender, introduced differential bias in self-reported information on sedentary behavior and MVPA among blue-collar workers. This result suggests that bias correction in future studies based on self-reports of sedentary time and MVPA should account for LBP and age.

Objectives We aimed at developing and evaluating statistical models predicting objectively measured occupational time spent sedentary or in physical activity from self-reported information available in large epidemiological studies and surveys.

Methods Two-hundred-and-fourteen blue-collar workers responded to a questionnaire containing information about personal and work related variables, available in most large epidemiological studies and surveys. Workers also wore accelerometers for 1-4 days measuring time spent sedentary and in physical activity, defined as non-sedentary time.Least-squares linear regression models were developed, predicting objectively measured exposures from selected predictors in the questionnaire.

Results A full prediction model based on age, gender, BMI, job group, self-reported occupational physical activity, and self-reported occupational sedentary time explained 63% (R² adjusted) of the variance of both objectively measured occupational sedentary time and physical activity time since these two exposures were complementary. Single-predictor models based only on self-reported information about either occupational physical activity or occupational sedentary time explained21% and 38%, respectively, of the variance of the objectively measured exposures. Internal validation using bootstrapping suggested that the full and single-predictor models would show almost the same performance in new data sets as in that used for modelling.

Conclusions Both full and single-predictor models based on self-reported information typically available in most large epidemiological studies and surveys were able to predict objectively measured occupational time spent sedentary or in physical activity, with explained variances ranging from 21% to 63%.

Objectives

The aims of this study were to (i) identify trajectories of neck-shoulder pain (NSP) over one year in an occupational population and (ii) determine whether these trajectories are predicted by NSP characteristics as well as personal and occupational factors at baseline.

Methods

This longitudinal study was conducted among Danish workers (N=748) from 2012-2014. Text messages were used to collect frequent data on NSP over one year (14 waves in total). Peak NSP intensity in the past month was rated on a 0-10 numeric scale. A baseline questionnaire covered NSP characteristics (pain intensity, duration, comorbidity, pain medication, and pain interference) as well as personal (age, gender, body mass index) and occupational (seniority, work type, physical strain at work) factors. Latent class growth analysis was used to distinguish trajectories of NSP. Multivariate regression models with odds ratios (OR) were constructed to predict trajectories of NSP.

Results

Six distinct trajectories of NSP were identified (asymptomatic 11%, very low NSP 10%, low recovering NSP 18%, moderate recovering NSP 28%, strong fluctuating NSP 24% and severe persistent NSP 9% of the workers). Female gender, age, physical strain at work, NSP intensity and duration, pain medication, and pain interference in daily work at baseline were positively associated with severe persistent NSP and strong fluctuating NSP (all P<0.05). Altogether, personal and occupational factors accounted for 14% of the variance, while NSP characteristics accounted for 54%.

Conclusions

In an occupational sample, six distinct trajectories of NSP were identified. Physical strain at work appears to be a pertinent occupational factor predicting strong fluctuating and severe persistent NSP.

Objectives The aim of this study was to examine the association between long-term sickness absence (LTSA) due to mental disorders and musculoskeletal disorders and all-cause disability pension (DP) among blue- and white-collar workers. A secondary objective was to examine the influence of familial factors on the associations. Methods This was a prospective twin cohort study of 42 984 individuals (21-64 years at baseline), 3017 of whom had a new LTSA spell (>14 days) due to mental or musculoskeletal disorders in 2005-2006. Average follow-up time was 5.4 years. Survey data on occupational class and register data on LTSA and DP were used. Cox proportional hazards regression was applied to calculate hazards ratios (HR) with 95% confidence intervals (CI). Results During follow-up, 989 participants went on disability. LTSA due to mental disorders and musculoskeletal disorders led to similar HR for DP among both white- and blue-collar workers when compared to white-collar workers not on LTSA (reference group). LTSA >= 6 months due to musculoskeletal disorders was associated with a higher risk of DP for white-collar (HR 31.50, 95% CI 20.45-48.52) than blue-collar (HR 17.64, 95% CI 13.08-23.78) workers when compared to the reference group. HR were lower in the discordant twin pair models for LTSA due to mental disorders than in the whole cohort. Conclusions White-collar workers on LTSA due to musculoskeletal disorders are especially vulnerable to all-cause DP. This pattern was not present for LTSA due to mental disorders. Familial factors seem to influence the association between LTSA due to mental disorders and all-cause DP.

Objectives

In spite of preventive efforts, organizations and employees face several challenges related to working life and occupational health, such as a substantial prevalence of musculoskeletal disorders, social inequality in health and physical capacity, multi-morbidity, an obesity epidemic and an aging workforce. We argue that a new approach for occupational ergonomics and health is required, going beyond prevention of harm caused by work. We propose the ´Goldilocks Principle´ as a new approach of how productive work can be designed to literally promote health and physical capacity.

Methods                 

Physical (in)activity profoundly influences health and physical capacity, with effects depending on the extent and temporal structure of the (in)activity. Like the porridge, chair and bed that needed to be ‘just right’ for Goldilocks in the fairy-tale of ´The Three Bears´, physical activity during productive work needs to be ‘just right’ for promoting rather than deteriorating health and capacity. In many jobs, physical activity is, however, either ’too much/high/frequent’ or ’too little/low/infrequent’ to give positive biomechanical and cardiometabolic stimuli.

Results

The paper presents the rationale, concept, development, application and prospects of the Goldilocks Principle for how productive work can be designed to promote health and physical capacity.

Conclusions

We envision a great potential to promote health and physical capacity by designing productive work according to the Goldilocks Principle, thus leading to benefits with respect to the current challenges related to working life and occupational health for society, organizations and employees.

Objectives We aimed to identify eldercare wards with different types of resident handling characteristics (‘phenotypes’) and determine the prospective association between these characteristics and musculoskeletal pain and sickness absence among workers during a one-year follow-up.

Methods Our study was based on the DOSES cohort, including 467 workers at 103 eldercare wards. At baseline, resident handlings were assessed using onsite observations. Workers’ self-reported musculoskeletal pain and sickness absence were assessed during the following year using text messages. Observations of the frequency of handlings per shift, use of assistive devices, assistance from others, and barriers (interruptions and impediments) were estimated for each worker, aggregated at ward level, and entered into a latent profile analysis, identifying ward phenotypes. We then used generalized estimating equations to determine associations between ward phenotypes, musculoskeletal pain and sickness absence.

Results We identified four ward phenotypes: ‘turbulent’ (many handlings with devices and assistance, many barriers), ‘strained’ (many handlings without devices or assistance, some barriers), ‘unpressured’ (few handlings, yet without devices or assistance, few barriers) and ‘balanced’ (some handlings with devices and assistance, some barriers). Compared to workers in balanced wards, workers in turbulent wards had more days with neck-shoulder and low-back pain (LBP); and those working in strained wards had more days with LBP and higher pain intensities.

Conclusion We found that ward phenotypes based on resident handling characteristics were predictive of musculoskeletal pain and sickness absence over one year. This shows that organizational factors related to resident handling are important determinants of musculoskeletal health among eldercare workers.

Sitting at work is suggested to increase risk for low-back pain (LBP). Thus, an association between temporal patterns of sitting and time course of LBP, across 12 months, among 665 participants from the DPhacto cohort was conducted. We found that longer durations of total and temporal sitting periods at work were significantly associated with a favorable time course of LBP.

Objectives. Low back pain (LBP) is a substantial health challenge, due to the risk for long term sickness absence and early retirement. Several biomechanical exposures at work, including sitting, have been suggested to increase the risk for LBP. The objective of this study was to determine the extent to which temporal patterns and total amount of objectively measured sitting is associated with LBP intensity, and whether selected modifiers influence these associations.

Methods. This cross sectional study uses baseline data from the Danish PHysical ACTivity cohort with objective measurements of physical activities in the cleaning, transport and manufacturing sectors. Peak intensity of LBP was collected by questionnaire on a 0-10 scale and sitting was expressed in terms of total duration and temporal pattern, i.e. time spent in brief bursts (≤5 minutes), moderate periods (>5 – ≤20 minutes) and prolonged periods of sitting (>20 minutes); both during work and whole day (waking hours only). Associations were determined using linear regression in models accounting for moderation and confounding. Factors evaluated as moderators or confounders were assessed by questionnaire.

Results. The population consisted of 704 participants. No significant associations were found between total duration or temporal patterns of sitting and LBP intensity, neither during work nor for the whole day. Body Mass Index significantly moderated the association between sitting and LBP; participants with a high and low BMI showing a negative and positive association, respectively.

Conclusion. Sitting was not independently associated with peak LBP intensity, suggesting other exposures to be more powerful risk factors for LBP.

Objectives

Contrary to leisure-time physical activity, occupational physical activity (OPA) may have harmful health effects, called the physical activity paradox. A proposed mechanism is that OPA can elevate the heart rate (HR) for several hours per day. We aimed to investigate the association between the mean intensity of OPA and HR variability (HRV) indices the following night.

Methods

Three cohorts (NOMAD, DPhacto, and Physical Workload and Fitness) involving blue-collar workers front different sectors were merged in this study. HR monitors (Actiheart) recorded 24-hour inter-beat intervals (IBI) for up to four consecutive days. The relative intensity of the mean HR during work was estimated by HR reserve (%HRR), and time-domain indices of HRV were analyzed during the following night. Data were analyzed using a multilevel growth model to test the association between mean %HRR during work and HRV indices at night in a day-by-day analysis adjusted for age, BMI, alcohol consumption, smoking, and occupation.

Results

The dataset included a sample of 878 Danish blue-collar workers, with a mean %HRR during work of 31%, and 42% worked at an intensity >= 30%HRR. The multilevel model showed negative within- and between-subject associations between %HRR during work and HRV indices at night.

Conclusions

Our results indicate a higher %HRR during work to associate with lower HRV indices the following night and a higher HR, reflecting an imbalanced autonomic cardiac modulation. This finding supports a high mean HR during work to be a potential underlying mechanism for the harmful health effect of OPA.

OBJECTIVES - The goal of this study was to examine the effect of rotating three-shift work on the circadian distribution of dietary intake and to investigate the relationships between displaced eating and nutritional status variables [blood lipids, blood glucose, body mass index (BMI)]. METHODS - Dietary data were collected by 147 replicate 24-h dietary recalls from 22 male industrial workers in rotating three-shift work. The intakes of energy and nutrients were estimated by the use of a nutrient data base. The BMI was calculated, and blood glucose, serum triglycerides, high-density lipoprotein (HDL) cholesterol and low-density lipoprotein (LDL) cholesterol were measured once. RESULTS - The dietary intakes of energy, protein, total fat, saturated fat, total carbohydrates, sucrose, and dietary fibre did not differ between 24-h periods but did differ between work shifts and were lowest during the night. Correlation analyses between dietary intakes and nutritional status parameters showed that those who redistributed their eating most to the night shift had higher levels of serum total cholesterol and LDL and a higher LDL:HDL ratio; 63% of the LDL cholesterol level was explained by carbohydrate intake during night shifts. In contrast, the total intake for whole 24-h periods or across entire shift cycles was not related to serum variables or BMI. CONCLUSIONS - Dietary intake is lower during night shifts (34-37% of 24-h intake of various nutrients) than during morning shifts (43-47%) and afternoon shifts (47-59%). The redistribution of food intake to the night may be associated with metabolic disturbances in lipid metabolism.

Objective. The aim of this study was to assess the association between occupational biomechanical exposures and the occurrence of surgical treatment for subacromial impingement syndrome (SIS).

Methods. A cohort of 220 295 male constructions workers who participated in a national occupational health surveillance program (1971–1993) were examined prospectively over a 16-year follow-up period (2001–2016) for surgically treated SIS. Worker job title, smoking status, height, weight, and age were registered on health examination. Job titles were mapped to 21 occupational groups based on tasks and training. A job exposure matrix (JEM) was developed with exposure estimates for each occupational group. Surgical cases were determined through linkage with the Swedish national in- and outpatient registers. Poisson regression was used to assess the relative risks (RR) for each biomechanical exposure.

Results. The total incidence rate of surgically treated SIS over the 16-year observation period was 201.1 cases per 100 000 person-years. Increased risk was evident for workers exposed to upper-extremity loading (push/pull/lift) (RR 1.45–2.30), high hand grip force (RR 1.47–2.23), using handheld tools (RR 1.52–2.09), frequent work with hands above shoulders (RR 1.62–2.11), static work (RR 1.77–2.26), and hand-arm vibration (RR 1.78–2.13). There was an increased risk for SIS surgery for all occupational groups (construction trades) compared with white-collar workers (RR 1.56–2.61).

Conclusions. Occupational upper-extremity load and posture exposures were associated with increased risk for surgical treatment of SIS, which underlines the need for reducing workplace exposures and early symptom detection in highly exposed occupational groups.

Compared to individuals who work during the day, shift workers are at higher risk of a range of metabolic disorders and diseases (eg, obesity, cardiovascular disease, peptic ulcers, gastrointestinal problems, failure to control blood sugar levels, and metabolic syndrome). At least some of these complaints may be linked to the quality of the diet and irregular timing of eating, however other factors that affect metabolism are likely to play a part, including psychosocial stress, disrupted circadian rhythms, sleep debt, physical inactivity, and insufficient time for rest and revitalization. In this overview, we examine studies on food and nutrition among shift workers [ie, dietary assessment (designs, methods, variables) and the factors that might influence eating habits and metabolic parameters]. The discussion focuses on the quality of existing dietary assessment data, nutritional status parameters (particularly in obesity), the effect of circadian disruptions, and the possible implications for performance at work. We conclude with some dietary guidelines as a basis for managing the nutrition of shift workers.

OBJECTIVES: This study examined the validity of a common belief in epidemiology with respect to work-related musculoskeletal disorders, that individual mechanical job exposure is better estimated from tasks performed in the job than from the mean exposure of the occupational group. METHODS: Whole-day recordings of upper trapezius electromyography were obtained from 24 cleaners and 23 office workers. Trapezius activity was analyzed in the level (gap time) and frequency (jerk time) dimensions. On the same day, the job of each person was divided into periods of active work and breaks by means of continuous observations. The bootstrap re-sampling technique was used with this database to compare task-based job exposure estimates with estimates based on the occupational mean. For a particular person, the task-based estimate was obtained by combining the average work and break exposures in the occupation with the personal time proportions of the two tasks in the job. RESULTS: The task-based estimates were, in general, equivalent to, or less correct than, occupation-based estimates for both exposure parameters in both occupations and for individual exposures, as well as for group means. This was the result in spite of significant and consistent exposure differences between work and breaks, in particular among the cleaners. CONCLUSIONS: Even if task exposure contrasts are large, task-based estimates of job exposures can be less correct than estimates based on the occupational mean. Since collecting and processing task information is costly, it is recommended that task-based modeling of mechanical exposure be implemented in studies only after careful examination of its possible benefits.

Objectives This experimental pilot study assessed the effects of sustained low-level accommodative vergence loads on oculomotor performance, eyestrain, and musculoskeletal functioning.

Methods A high-contrast fixation-point stimulus [light-emitting diode (LED)] was introduced into the optical axis of the viewing eye or into the midline in case of binocular viewing. The participants (N=6) were asked to compensate for the blur incurred by adjusting the strength of their eye lens. The participants performed in the following three standardized sequential viewing tasks: (i) resting with eyes open in darkness, (ii) accommodating alternately on a near versus a far LED illuminated sequentially (near–far response), and (iii) sustained fixation upon a LED at near. After the third task, the first and second tasks were repeated once.

Results The main effects of the third task were to decrease the overall rate of binocular accommodative relaxation time (diopters/s) in the repetition of the second task trial. The baseline shifts in individual response times also correlated with changes in the response amplitudes under the binocular stimulus conditions, which required contraction of the ciliary muscle.

Conclusions The results taken as a whole validate a technique of essential interest to applied vision research.

Objectives

The aim of this study was to investigate associations between psychosocial working conditions, occupational groups defined by sector, and disability pension (DP) with mental diagnoses while accounting for familial confounding.

Methods

A prospective population-based cohort study was conducted, including all Swedish twins who, in January 1993, were living and working in Sweden and not on old-age pension or DP (N=42 715). The twins were followed from 1993–2008 regarding DP. Data on DP, exposures, and covariates were obtained from national registries. Cox proportional hazards regression models with hazard ratios (HR) and 95% confidence intervals (95% CI) were constructed for the whole cohort, and for discordant twin pairs.

Results

The associations for the whole cohort between DP with mental diagnoses and (i) job demands (HR 1.23, 95% CI 1.06–1.43), (ii) job control (HR 0.91, 95% CI 0.83–0.99), (iii) healthcare and social work (HR 1.41, 95% CI 1.04–1.92), and (iv) service and military work (HR 2.07, 95% CI 1.37–3.14) remained after accounting for possible confounders, including familial factors, while the associations between DP and (i) social support, (ii) type of jobs, and (iii) some of the occupational groups were attenuated, becoming non-significant. In the discordant twin pair analyses, commercial work was significantly associated with lower risk of DP (HR 0.55, 95% CI 0.32–0.95).

Conclusions

One unit increase in job demands and working in the occupational groups healthcare and social work or service and military work seem to be risk factors of DP with mental diagnoses, independent from various background factors including familial ones. However, one unit increase in job control or working in commercial work seem to be protective factors of such DP, accounting for confounding factors of this study.

Objectives: This systematic review aimed to identify published observational methods assessing biomechanical exposures in occupational settings and evaluate them with reference to the needs of different users.

Methods: We searched scientific databases and the internet for material from 1965 to September 2008. Methods were included if they were primarily based on the systematic observation of work, the observation target was the human body, and the method was clearly described in the literature. A systematic evaluation procedure was developed to assess concurrent and predictive validity, repeatability, and aspects related to utility. At least two evaluators independently carried out this evaluation.

Results: We identified 30 eligible observational methods. Of these, 19 had been compared with some other method(s), varying from expert evaluation to data obtained from video recordings or through the use of technical instruments. Generally, the observations showed moderate-to-good agreement with the corresponding assessments made from video recordings; agreement was the best for large-scale body postures and work actions. Postures of wrist and hand as well as trunk rotation seemed to be more difficult to observe correctly. Intra- and inter-observer repeatability were reported for 7 and 17 methods, respectively, and were judged mostly to be moderate or good.

Conclusions: With training, observers can reach consistent results on clearly visible body postures and work activities. Many observational tools exist, but none evaluated in this study appeared to be generally superior. When selecting a method, users should define their needs and assess how results will influence decision-making

Objectives: This study compared the cost-efficiency of observation and inclinometer assessment of trunk and upper arm inclination in a population of flight baggage handlers, as an illustration of a general procedure for addressing the trade-off between resource consumption and statistical performance in occupational epidemiology.

Methods:  Trunk and upper arm inclination with respect to the line of gravity were assessed for 3 days on each of 27 airport baggage handlers using simultaneous recordings by inclinometers and video.  Labour and equipment costs associated with data collection and data processing were tracked throughout.  Statistical performance, in terms of the inverse of the standard deviation and root mean squared error of the group mean exposure, was computed from the variance components within and between workers, and bias (with inclinometer assumed to produce ‘correct’ inclination angles).  The behavior of the trade-off between cost and efficiency with changed sample size, as well as with changed logistics for data collection and processing, was investigated using simulations.

Results:  At similar total costs, time spent at trunk and arm inclination angles greater than 60 degrees as well as 90^th percentile arm inclination were estimated at higher precision using inclinometers, while median inclination and 90^th percentile trunk inclination was determined more precisely using observation.  This hierarchy persisted in a scenario where the study was immediately reproduced in another population, while inclinometry was more cost-efficient than observation for all three posture variables in a scenario where data were already collected and only needed to be processed. Observations showed to be biased relative to the –assumed to be correct – inclinometer data, and so inclinometry became the most cost-efficient option for all posture variables and irrespective of scenario when statistical performance was measured by bias and precision combined.

Conclusions: Inclinometers were more cost-efficient in use than observation for two out of three posture metrics investigated when statistical performance was measured only in terms of precision. Since observations were biased, inclinometers consistently outperformed observation when both bias and precision were included in statistical performance. The presented general model for assessing cost-efficiency may be used for designing exposure assessment strategies with considerations not only to statistical criteria, but even to costs. The empirical data provide a specific basis for planning assessments of working postures in occupational groups.

Objectives: Work-related musculoskeletal disorders (MSD) are highly prevalent and put a large burden on the (working) society. Primary prevention of work-related MSD focuses often on physical risk factors (such as on manual lifting and awkward postures), but has not been too successful in reducing the MSD burden. This may partly be caused by insufficient knowledge of etiological mechanisms and/or a lack of adequately feasible interventions (theory failure and program failure, respectively), possibly due to limited integration of research disciplines. A research framework could link research disciplines thereby strengthening the development and implementation of preventive interventions. Our objective was to define and describe such a framework for multi-disciplinary research on work-related MSD prevention.

Methods: We described a framework for MSD prevention research, partly based on frameworks from other research fields (i.e., sports injury prevention and public health).

Results: The framework is composed of a repeated sequence of six steps comprising the assessment of 1) incidence and severity of MSD, 2) risk factors for MSD, and 3) underlying mechanisms; and the 4) development, 5) evaluation, and 6) implementation of preventive intervention(s).

Conclusions: In the present framework for optimal work-related MSD prevention, research disciplines are linked. This framework can thereby help to improve theories and strengthen the development and implementation of prevention strategies for work-related MSD.

Objective In contrast to several previous papers dealing with the structure and effects of ergonomics interventions, this systematic literature review focuses on the theories concerning change processes upon which these interventions – implicitly or explicitly – have been based.

Methods In a systematic search of 13 literature databases, 30 peer-reviewed intervention studies published between 2000–2007 were identified that provided sufficient information for the change process theory to be identified.

Results Thirteen studies referred to an explicit theory of change, the most common being participatory theory, while in 17 studies, the change theory could only be discerned indirectly from the described intervention strategy. Twenty-five studies explained the reason for choosing their strategy, with a clear reference to theory or previous research, whereas five provided only a weak background. Four categories of intervention strategies for change were identified: (i) changes targeting the individual, (ii) changes focusing on the work environment, (iii) changes relying on interactions between people, and (iv) structural and organizational changes.

Conclusions A strikingly small proportion of ergonomics intervention studies have explained the theory behind the expected change process. A better awareness of the assumptions about change processes embedded in intervention strategies – whether implicit or explicit – may help in identifying and examining those ideas and processes that promote or restrict successful implementation. Such knowledge, in turn, can contribute to the development of interventions that are thoughtfully designed and effectively implemented.