| 1. |
- Dalbøge, Annett, et al.
(författare)
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Upper arm elevation and repetitive shoulder movements : A general population job exposure matrix based on expert ratings and technical measurements
- 2016
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Ingår i: Occupational and Environmental Medicine. - : BMJ. - 1351-0711 .- 1470-7926. ; 73:8, s. 553-560
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Tidskriftsartikel (refereegranskat)abstract
- Objectives We recently constructed a general population job exposure matrix (JEM), The Shoulder JEM, based on expert ratings. The overall aim of this study was to convert expert-rated job exposures for upper arm elevation and repetitive shoulder movements to measurement scales. Methods The Shoulder JEM covers all Danish occupational titles, divided into 172 job groups. For 36 of these job groups, we obtained technical measurements (inclinometry) of upper arm elevation and repetitive shoulder movements. To validate the expert-rated job exposures against the measured job exposures, we used Spearman rank correlations and the explained variance according to linear regression analyses (36 job groups). We used the linear regression equations to convert the expert-rated job exposures for all 172 job groups into predicted measured job exposures. Bland-Altman analyses were used to assess the agreement between the predicted and measured job exposures. Results The Spearman rank correlations were 0.63 for upper arm elevation and 0.64 for repetitive shoulder movements. The expert-rated job exposures explained 64% and 41% of the variance of the measured job exposures, respectively. The corresponding calibration equations were y=0.5%time+0.16×expert rating and y=27°/s+0.47×expert rating. The mean differences between predicted and measured job exposures were zero due to calibration; the 95% limits of agreement were ±2.9% time for upper arm elevation >90° and ±33°/s for repetitive shoulder movements. Conclusions The updated Shoulder JEM can be used to present exposure-response relationships on measurement scales.
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| 2. |
- Heilskov-Hansen, Thomas, et al.
(författare)
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Exposure-response relationships between movements and postures of the wrist and carpal tunnel syndrome among male and female house painters : a retrospective cohort study
- 2016
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Ingår i: Occupational and Environmental Medicine. - : BMJ. - 1470-7926 .- 1351-0711. ; 73:6, s. 401-408
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To investigate exposure-response relationships between measured movements and postures of the wrist and the incidence of carpal tunnel syndrome (CTS), and any modifications by sex.METHODS: In 2011, we established a historical cohort of 9364 members of the Painters' Union in Denmark. Self-reported task distributions were obtained by questionnaire (53% responded) and combined with sex-specific task exposure matrices to get individual estimates of exposure intensity, that is, velocity of wrist flexion/extension, mean power frequency (MPF) and non-neutral wrist postures. Exposure duration was assessed from yearly working proportions. Registered first-time hospital discharge CTS diagnoses and CTS surgery were collected as outcomes. The cohort was followed from 1994 to 2010. Log-linear Poisson regression was used.RESULTS: For CTS diagnoses, the adjusted incidence rate ratios (IRRs) increased with increasing wrist velocity (IRR=1.37 (95% CI 1.10 to 1.71) per °/s) and MPF (IRR=1.53 (95% CI 1.21 to 1.91) per 0.01 Hz). For CTS surgery, the results were similar. The outcomes were not related to non-neutral postures or exposure duration. The adjusted IRRs for women were higher than those for men. There were no multiplicative interaction effects between exposure intensity, exposure duration and sex. However, the absolute incidence rates (IRs) increased at a steeper rate for women than for men, indicating an additive interaction.CONCLUSIONS: The incidence of CTS increased with increasing velocity of wrist flexion/extension and MPF of wrist movements. The relative increase in incidence rates was the same for women and men, but the absolute incidence rates increased at a steeper rate for women than for men.
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| 3. |
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| 4. |
- Liv, Per, et al.
(författare)
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Accuracy and precision of variance components in occupational posture recordings : a simulation study of different data collection strategies
- 2012
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Ingår i: BMC Medical Research Methodology. - : Springer Science and Business Media LLC. - 1471-2288. ; 12:1, s. 58-58
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Tidskriftsartikel (refereegranskat)abstract
- Background. Information on exposure variability, expressed as exposure variance components, is of vital use in occupational epidemiology, including informed risk control and efficient study design. While accurate and precise estimates of the variance components are desirable in such cases, very little research has been devoted to understanding the performance of data sampling strategies designed specifically to determine the size and structure of exposure variability. The aim of this study was to investigate the accuracy and precision of estimators of betweensubjects, between-days and within-day variance components obtained by sampling strategies differing with respect to number of subjects, total sampling time per subject, number of days per subject and the size of individual sampling periods. Methods. Minute-by-minute values of average elevation, percentage time above 90degrees and percentage time below 15degrees were calculated in a data set consisting of measurements of right upper arm elevation during four full shifts from each of 23 car mechanics. Based on this parent data, bootstrapping was used to simulate sampling with 80 different combinations of the number of subjects (10, 20), total sampling time per subject (60, 120, 240, 480 minutes), number of days per subject (2, 4), and size of sampling periods (blocks) within days (1, 15, 60, 240 minutes). Accuracy (absence of bias) and precision (prediction intervals) of the variance component estimators were assessed for each simulated sampling strategy. Results. Sampling in small blocks within days resulted in essentially unbiased variance components. For a specific total sampling time per subject, and in particular if this time was small, increasing the block size resulted in an increasing bias, primarily of the between-days and the within-days variance components. Prediction intervals were in general wide, and even more so at larger block sizes. Distributing sampling time across more days gave in general more precise variance component estimates, but also reduced accuracy in some cases. Conclusions. Variance components estimated from small samples of exposure data within working days may be both inaccurate and imprecise, in particular if sampling is laid out in large consecutive time blocks. In order to estimate variance components with a satisfying accuracy and precision, for instance for arriving at trustworthy power calculations in a planned intervention study, larger samples of data will be required than for estimating an exposure mean value with a corresponding certainty
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| 5. |
- Liv, Per, 1979-, et al.
(författare)
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Theoretical and empirical efficiency of sampling strategies for estimating upper arm elevation
- 2011
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 0003-4878 .- 1475-3162. ; 55:4, s. 436-449
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To investigate the statistical efficiency of strategies for sampling upper arm elevation data, which differed with respect to sample sizes and sample allocations within and across measurement days. The study was also designed to compare standard theoretical predictions of sampling efficiency, which rely on several assumptions about the data structure, with 'true' efficiency as determined by bootstrap simulations.METHODS: Sixty-five sampling strategies were investigated using a data set containing minute-by-minute values of average right upper arm elevation, percentage of time with an arm elevated <15°, and percentage of time with an arm elevated >90° in a population of 23 house painters, 23 car mechanics, and 26 machinists, all followed for four full working days. Total sample times per subject between 30 and 240 min were subdivided into continuous time blocks between 1 and 240 min long, allocated to 1 or 4 days per subject. Within day(s), blocks were distributed using either a random or a fixed-interval principle. Sampling efficiency was expressed in terms of the variance of estimated mean exposure values of 20 subjects and assessed using standard theoretical models assuming independence between variables and homoscedasticity. Theoretical performance was compared to empirical efficiencies obtained by a nonparametric bootstrapping procedure.RESULTS: We found the assumptions of independence and homoscedasticity in the theoretical model to be violated, most notably expressed through an autocorrelation between measurement units within working days. The empirical variance of the mean exposure estimates decreased, i.e. sampling efficiency increased, for sampling strategies where measurements were distributed widely across time. Thus, the most efficient allocation strategy was to organize a sample into 1-min block collected at fixed time intervals across 4 days. Theoretical estimates of efficiency generally agreed with empirical variances if the sample was allocated into small blocks, while for larger block sizes, the empirical 'true' variance was considerably larger than predicted by theory. Theory overestimated efficiency in particular for strategies with short total sample times per subject.CONCLUSIONS: This study demonstrates that when exposure data are autocorrelated within days-which we argue is the major reason why theory overestimates sampling performance-sampling efficiency can be improved by distributing the sample widely across the day or across days, preferably using a fixed-interval strategy. While this guidance is particularly valid when small proportions of working days are assessed, we generally recommend collecting more data than suggested by theory if a certain precision of the resulting exposure estimate is needed. More data per se give a better precision and sampling larger proportion(s) of the working day(s) also alleviate the negative effects of possible autocorrelation in data.
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| 6. |
- Meyland, Jacob, et al.
(författare)
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Sex differences in muscular load among house painters performing identical work tasks
- 2014
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 114:9, s. 1901-1911
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Tidskriftsartikel (refereegranskat)abstract
- The present study aimed to estimate possible differences in upper body muscular load between male and female house painters performing identical work tasks. Sex-related differences in muscular load may help explain why women, in general, have more musculoskeletal complaints than men. In a laboratory setting, 16 male and 16 female house painters performed nine standardised work tasks common to house painters. Unilateral electromyography (EMG) recordings were obtained from the supraspinatus muscle by intramuscular electrodes and from the trapezius, extensor and flexor carpi radialis muscles by surface electrodes. Relative muscular loads in %EMG(max) as well as exerted force in Newton, based on ramp calibrations, were assessed. Sex differences were tested using a mixed model approach. Women worked at about 50 % higher relative muscular loads than men in the supraspinatus and forearm muscles at all percentiles and in all tasks. Women exerted about 30 % less force in the trapezius muscle at the 50th percentile. Female house painters had a higher relative muscular load than their male colleagues without exerting more force. The effects of a higher relative muscular load accumulated over years of work may in part explain why musculoskeletal complaints in the upper body occur more frequently among women than men.
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| 7. |
- Svendsen, Susanne Wulff, et al.
(författare)
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Work above shoulder level and degenerative alterations of the rotator cuff tendons : a magnetic resonance imaging study.
- 2004
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Ingår i: Arthritis and rheumatism. - : Wiley. - 0004-3591 .- 1529-0131. ; 50:10, s. 3314-22
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To determine whether work performed with the arms in a highly elevated position is associated with alterations in the rotator cuff tendons as assessed by magnetic resonance imaging (MRI). METHODS: A cross-sectional study was performed in a historical cohort of male machinists, car mechanics, and house painters. The participants were right-handed, ages 40-50 years, and had been employed in their trades for not less than 10 years. Seventy-one percent of invited subjects participated (136 of 192). Lifetime upper arm elevation was assessed by direct measurements combined with individual work histories obtained by questionnaire and from registry data. Supraspinatus tendinopathy was evidenced by MRI signal intensity changes and morphologic alterations. Infraspinatus and subscapularis tendinopathy were also assessed. Additional outcomes were acromioclavicular joint degeneration and humeral head cysts. The MRI findings were evaluated by radiologists who were blinded to exposure status and symptoms. RESULTS: An exposure-response relationship was found between lifetime upper arm elevation and supraspinatus tendinopathy, with an age-adjusted odds ratio of 1.27 (95% confidence interval 1.02-1.60) for a 5-month increase in the total number of full-time working months spent with the arm elevated >90 degrees . CONCLUSION: Work with the arms in a highly elevated position is associated with MRI-diagnosed alterations in the supraspinatus tendon. By demonstrating the first part of a possible biologic pathway, the study corroborates the work-relatedness of rotator cuff disorders.
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| 8. |
- Tabatabaeifar, Sorosh, et al.
(författare)
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Reversible median nerve impairment after three weeks of repetitive work
- 2017
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Ingår i: Scandinavian Journal of Work, Environment and Health. - : Scandinavian Journal of Work, Environment and Health. - 0355-3140 .- 1795-990X. ; 43:2, s. 163-170
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Tidskriftsartikel (refereegranskat)abstract
- Objectives The aim of this study was to evaluate the development of impaired median nerve function in relation to hand-intensive seasonal work. We hypothesized that at end-season, median nerve conduction would be impaired and then recover within weeks. Methods Using nerve conduction studies (NCS), we examined median nerve conduction before, during, and after engaging in 22 days of mink skinning. For a subgroup, we used goniometry and surface electromyography to characterize occupational mechanical exposures. Questionnaire information on symptoms, disability, and lifestyle factors was obtained. Results The study comprised 11 male mink skinners with normal median nerve conduction at pre-season (mean age 35.7 years, mean number of seasons with skinning 8.9 years). Mink skinning was characterized by a median angle of wrist flexion/extension of 16º extension, a median velocity of wrist flexion/extension of 22 °/s, and force exertions of 11% of maximal voluntary electrical activity. At end-season, mean distal motor latency (DML) had increased 0.41 ms (P<0.001), mean sensory nerve conduction velocity (SNCV) digit 2 had decreased 6.3 m/s (P=0.004), and mean SNCV digit 3 had decreased 6.2 m/s (P=0.01); 9 mink skinners had decreases in nerve conduction, 5 fulfilled electrodiagnostic criteria and 4 fulfilled electrodiagnostic and clinical criteria (a positive Katz hand diagram) for carpal tunnel syndrome (CTS). Three to six weeks post-season, the changes had reverted to normal. Symptom and disability scores showed corresponding changes. Conclusions In this natural experiment, impaired median nerve conduction developed during 22 days of repetitive industrial work with moderate wrist postures and limited force exertion. Recovery occurred within 3–6 weeks post-season.
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