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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
Curtin University, Perth, Australia; VU University Amsterdam, the Netherlands; Body@Work, Research Center on Physical Activity, Work and Health, the Netherlands.
University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences. University of Gävle, Centre for Musculoskeletal Research.ORCID iD: 0000-0003-1443-6211
VU University Amsterdam, the Netherlands; Body@Work, Research Center on Physical Activity, Work and Health, the Netherlands.
Body@Work, Research Center on Physical Activity, Work and Health, the Netherlands; EMGO Institute, VU University Medical Center, Amsterdam, the Netherlands.
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2015 (English)In: Annals of Occupational Hygiene, ISSN 0003-4878, E-ISSN 1475-3162, Vol. 59, no 4, 439-454 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2015. Vol. 59, no 4, 439-454 p.
Keyword [en]
epidemiology, ergonomics, exposure, exposure assessment, group-based measurement strategy, low-back pain, musculoskeletal injury, precision
National Category
Environmental Health and Occupational Health
Identifiers
URN: urn:nbn:se:hig:diva-14246DOI: 10.1093/annhyg/meu102ISI: 000355625800004PubMedID: 25433002Scopus ID: 2-s2.0-84929454897OAI: oai:DiVA.org:hig-14246DiVA: diva2:620188
Funder
Forte, Swedish Research Council for Health, Working Life and Welfare, 2009-1761
Available from: 2013-05-07 Created: 2013-05-07 Last updated: 2016-03-22Bibliographically approved

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CiteExportLink to record
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