Bias in risk estimates from variability of exposure to postural load on the back in occupational groups.

Standing at work and progression of carotid atherosclerosis

“…Workers tend to underestimate the amount of standing, and this tendency would introduce a conservative bias (68). The potential for bias due to measurement error has been shown to be lowest for prospective studies (72). No direct job observations were available in this population-based study, but we had the opportunity to check current occupational titles for all the subjects and found that the occupational titles were consistent with reported work positions.…”

Predictors of disability retirement

“…Other studies suggest that the correlation between self-reports and direct observation is not always satisfactory and differs by the type of work condition examined (20)(21)(22)(23)(24). The potential for bias has been shown to be lowest for prospective studies (25). Fourth, the assessment of prevalent diseases was based on an extensive and elaborate medical history and examination including a wide range of laboratory tests performed over a 2-day period.…”

Positive and negative evidence of risk factors for back disorders

“…The 4th reason for not finding significant associations is the presence of substantial uondifferential misclassification in the work-related risk factors. Inaccuracies in exposure categorization would tend to reduce the apparent association between the risk factor and back disorder (10,64). All the studies with no apparent associations relied on exposure estimates derived from self-administered questionnaires, and none of these studies presented information on the reliability of the exposure questions.…”