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- Coenen, Pieter, et al.
(författare)
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Bias and power in group-based epidemiologic studies of low-back pain exposure and outcome : effects of study size and exposure measurement efforts
- 2015
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 0003-4878 .- 1475-3162. ; 59:4, s. 439-454
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Exposure-outcome studies, for instance on work-related low-back pain (LBP), often classify workers into groups for which exposures are estimated from measurements on a sample of workers within or outside the specific study. The present study investigated the influence on bias and power in exposure-outcome associations of the sizes of the total study population and the sample used to estimate exposures.Methods: At baseline, lifting, trunk flexion, and trunk rotation were observed for 371 of 1131 workers allocated to 19 a-priori defined occupational groups. LBP (dichotomous) was reported by all workers during three years of follow-up. All three exposures were associated with LBP in this parent study (p<0.01).All 21 combinations of n=10,20,30 workers per group with an outcome, and k=1,2,3,5,10,15,20 workers actually being observed were investigated using bootstrapping, repeating each combination 10,000 times. Odds ratios (OR) with p-values were determined for each of these virtual studies. Average OR and statistical power (p<0.05 and p<0.01) was determined from the bootstrap distributions at each (n,k) combination.Results: For lifting and flexed trunk, studies including n≥20 workers, with k≥5 observed, led to an almost unbiased OR and a power >0.80 (p-level 0.05). A similar performance required n≥30 workers for rotated trunk. Small numbers of observed workers (k) resulted in biased OR, while power was, in general, more sensitive to the total number of workers (n).Conclusions: In epidemiologic studies using a group-based exposure assessment strategy, statistical performance may be sufficient if outcome is obtained from a reasonably large number of workers, even if exposure is estimated from only few workers per group.
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| 2. |
- Coenen, Pieter, et al.
(författare)
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Group-based exposuremeasurement strategies and their effects on trunk rotation and low-back pain exposure-outcome associations
- 2013
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Ingår i: Occupational & Environmental Medicine. - : BMJ Journals. ; , s. A101-A102
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Konferensbidrag (refereegranskat)abstract
- Objectives In epidemiological studies of occupational exposures (e.g. lifting) and low-back pain (LBP), group-based exposure measurement strategies are common. Workers are classified into exposure groups; exposure is measured only in a selection of workers in each group, and their mean exposure is assigned to all workers in the group. Exposure-outcome relationships are then determined by regression, relating exposure estimates with individual LBP data from all subjects. The objective of this study was to assess the effect of different group-based measurement strategies on exposure-outcome associations.Methods 1122 workers, classified into 19 groups on the basis of job-related exposure, participated in this study. In each group, videos were collected from ~25% of the workers (in total, 370 workers), and percentage of the work day spent in trunk rotation was estimated by observation of the videos. This estimate of trunk rotation was significantly associated with self-reported LBP during three years of follow-up (OR:1.43 (1.06–1.93)).Using a bootstrap simulation, workers per group (n = 10, 20, 30, 40) and percentage of observed workers (k = 10, 20, 30, 40, 50%) were varied. For each combination, (nk) workers were selected with replacement in each job group among those observed, and n (100-k) workers among those not observed. The mean exposure of the observed workers was assigned to all group members which was related to individual LBP data. ORs and accompanying p-level was estimated using logistic-regression.Results A group-based measurement protocol led to significant (p < 0.05) ORs when the total number of workers was larger than n = 30 in each job group, and ≥20% was actually observed.Conclusions The proportion of observed workers did have an effect on p-values, but it appeared weaker than that of changing the total group size. These results suggest that it may be sufficient to observe only a minor proportion of workers if the overall size of the population is reasonably large.
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| 4. |
- Coenen, Pieter, et al.
(författare)
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The effect of the presence and characteristics of an outlying group on exposure-outcome associations
- 2015
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Ingår i: Scandinavian Journal of Work, Environment and Health. - : Scandinavian Journal of Work, Environment and Health. - 0355-3140 .- 1795-990X. ; 41:1, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Main, Chris J., et al.
(författare)
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Implementation Science and Employer Disability Practices : Embedding Implementation Factors in Research Designs
- 2016
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Ingår i: Journal of occupational rehabilitation. - : Springer-Verlag New York. - 1053-0487 .- 1573-3688. ; 26:4, s. 448-464
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: For work disability research to have an impact on employer policies and practices it is important for such research to acknowledge and incorporate relevant aspects of the workplace. The goal of this article is to summarize recent theoretical and methodological advances in the field of Implementation Science, relate these to research of employer disability management practices, and recommend future research priorities.Methods: The authors participated in a year-long collaboration culminating in an invited 3-day conference, “Improving Research of Employer Practices to Prevent Disability”, held October 14–16, 2015, in Hopkinton, MA, USA. The collaboration included a topical review of the literature, group conference calls to identify key areas and challenges, drafting of initial documents, review of industry publications, and a conference presentation that included feedback from peer researchers and a question/answer session with a special panel of knowledge experts with direct employer experience.Results: A 4-phase implementation model including both outer and inner contexts was adopted as the most appropriate conceptual framework, and aligned well with the set of process evaluation factors described in both the work disability prevention literature and the grey literature. Innovative interventions involving disability risk screening and psychologically-based interventions have been slow to gain traction among employers and insurers. Research recommendations to address this are : (1) to assess organizational culture and readiness for change in addition to individual factors; (2) to conduct process evaluations alongside controlled trials; (3) to analyze decision-making factors among stakeholders; and (4) to solicit input from employers and insurers during early phases of study design.Conclusions: Future research interventions involving workplace support and involvement to prevent disability may be more feasible for implementation if organizational decision-making factors are imbedded in research designs and interventions are developed to take account of these influences.
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| 7. |
- Young, Amanda E., et al.
(författare)
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Workplace Outcomes in Work-Disability Prevention Research : A Review with Recommendations for Future Research
- 2016
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Ingår i: Journal of occupational rehabilitation. - New York, USA : Springer. - 1053-0487 .- 1573-3688. ; 26:4, s. 434-447
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Forskningsöversikt (refereegranskat)abstract
- Introduction: Outcome assessment is a central issue in work disability prevention research. The goal of this paper was to (1) ascertain the most salient workplace outcomes; (2) evaluate the congruence between business and science perspectives; (3) illustrate new perspectives on assessing longitudinal outcomes; and (4) provide recommendations for advancing outcome evaluation in this area of research.Methods: The authors participated in a year-long collaboration that culminated in a sponsored 3-day conference, "Improving Research of Employer Practices to Prevent Disability", held October 14-16, 2015, in Hopkinton, MA, USA. The collaboration included a topical review of the literature, group conference calls to identify key areas and challenges, drafting of initial documents, review of industry publications, and a conference presentation that included feedback from peer researchers and a question/answer session with a special panel of knowledge experts with direct employer experience.Results: Numerous workplace work-disability prevention outcome measures were identified. Analysis indicated that their applicability varied depending on the type of work disability the worker was experiencing. For those who were working, but with health-related work limitations (Type 1), predominant outcomes were measures of productivity, presenteeism, and work-related limitations. For those who were off work due to a health condition (Type 2), predominant outcomes were measures of time off work, supervisor/employee interactions, and return-to-work (RTW) preparation. For those who had returned to work (Type 3), predominant outcomes were measures of presenteeism, time until RTW, percentage of work resumption, employment characteristics, stigma, work engagement, co-worker interactions, and sustained or durable RTW. For those who had withdrawn from the labor force (Type 4), predominant outcomes were cost and vocational status.Discussion: Currently available measures provide a good basis to use more consistent outcomes in disability prevention in the future. The research area would also benefit from more involvement of employers as stakeholders, and multilevel conceptualizations of disability outcomes.
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