Skip to main content

Currently Skimming:

Methodological Issues and Approaches
Pages 65-82

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 65...
... For example, there are highly controlled studies of soft tissue responses to specific exposures that are based on work with cadavers, animal models, and human biomechanics. There are also surveys and other observational epidemiologic studies that examine the associations between musculoskeletal disorders and physical work and organizational, social, and individual factors.
From page 66...
... and discussed below, has been used in an earlier National Research Council report (1995~; it is particularly useful when considering causal inferences across different fields of study. RESEARCH PERSPECTIVES Basic Sciences From the perspective of basic sciences, studies are designed and performed to isolate discrete events that are carefully engineered to deliver a set of exposures characterized by replicable frequency, dose, and duration.
From page 67...
... . A key feature of measurement in observational epidemiologic studies is that the results are generated from populations of humans.
From page 68...
... In fact, observational epidemiologic studies use techniques from biostatistics to evaluate the degree of differences in the extraneous variables between the two groups and to perform statistical adjustment that makes these other factors similar. The goal of these statistical techniques is to control for confounding.
From page 69...
... Interventions From the perspective of intervention studies, investigations of human populations are designed on the basis of data from basic sciences and observational epidemiologic studies, to formally test whether reduction (or enhancement) of an exposure results in a lower incidence of a disorder (and an elevation of a state of well-being)
From page 70...
... Probably more important for workplace studies is the consideration that there is constant change at work, independent of any planned intervention, that makes the laborious process of planning and implementing a randomized controlled trial challenging, if not impractical. In these situations, another design, variously termed "historical control study," "before/after design" study, and "time-series analysis," has been used.
From page 71...
... This information provides the basis for developing interventions, including job redesign, that are aimed at reducing the frequency or some other characteristic of repetitive lifting. The successful intervention studies with job redesign that show a reduction in repetitive job lifting and a resultant reduction in the incidence of back disorders provide evidence for instituting activities in practice and for confirming that the repetitive lifting and back disorder were truly related.
From page 72...
... In the example used in this chapter, the exposure has been repetitive lifting, but one could study trunk bending, trunk twisting, temperature, and so on. In public health literature, the outcome is usually a disease condition for which risk factors are being sought in order to find strategies to prevent the disease.
From page 73...
... Temporal ordering may be difficult to establish in cross-sectional surveys because information about exposure and outcome are obtained during the same interview. The survey approach, though operationally efficient, is less powerful for generating causal inferences than a prospective study (e.g., that follows individuals who vary in terms of performing repetitive lifting and who are then followed systematically for development of back disorder)
From page 74...
... In this circumstance, the investigation could then identify a combination of risk factors that contribute to the outcome, each of which is important both alone and additively. Recognizing that the etiologic nature of many diseases, including musculoskeletal disorders, is likely to be multifactorial, scientists search for a "web of causation" (Susser, 1973~.
From page 75...
... This refers to the relationship of exposure and outcome in the presence of a third variable, whereby the primary association differs significantly across different levels of the third variable. While the association of the exposure and outcome may be impressive when viewed alone or when summarized across the levels of the third variable, closer examination reveals that the primary association is vastly larger at the first than at the second level of the third variable.
From page 76...
... In generating causal inferences, there must be considerable attention to errors in measurement. Random error can occur through imprecise measurement that allows a broader array of responses than would be necessary, whether through questionnaires or with an apparatus that captures information within a range of the true values.
From page 77...
... The emphasis in this discussion has not been on study design, but rather generic considerations that could apply to basic science, observational epidemiologic, and intervention studies. There is, however, an approach for considering a body of literature to generate causal inferences across a variety of studies.
From page 78...
... These criteria have been used in numerous other reports for the past 40 years and have represented important guidance for drawing etiologic causal inferences in studies of human disease that were characterized by the use of observational epidemiologic studies.
From page 79...
... . The data collection is usually passive, as when doctors complete forms to report diseases or conditions to the government or to insurance companies, or it can be active, with trained surveillance technicians conducting systematic surveys in selected settings using established protocols.
From page 80...
... Thus, the cross-sectional survey needs to be reviewed to determine whether the correlates identified represent suggestions for risk factors for the disease outcome, or represent correlates for survival in the population up to the point at which the study is done. The prospective study is a longitudinal design that starts with measuring exposure and then follows individuals over time to identify incidence of disease (or other outcome)
From page 81...
... The strength of this method is that, alone, self-reports of work practices in epidemiologic studies might be important but could be questioned as being subject to socially desirable responding; having data from other sources helps to strengthen inferences that this behavior occurred. Similarly, having a reduction in back disorders after implementing job redesign could be due to any number of factors, but having data to show that there was a decrease in specified biomechanical actions at the level of the individual bolsters confidence that the observed results might be due to the intervention.
From page 82...
... This pattern of evidence approach is not novel; it was described and used in a recent report that investigated the role of sterile syringes and bleach disinfection in HIV prevention (National Research Council, 1995~. This report reviews the literature on musculoskeletal disorders in the workplace, drawing on studies from basic sciences, epidemiology, and intervention research.


This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.