Diet and health risk: risk patterns and disease-specific associations.

Whether such epidemiologic descriptors as relative risk, dose response, and threshold points convey meaningful information is often the subject of debate. Thus, using these descriptors to juxtapose the many disease-specific effects of nutritional exposures becomes problematic. In this article it is argued that epidemiologic patterns of disease-exposure associations must be interpreted in light of the profound imprecision of exposure assessment that characterizes nutritional epidemiology. In general, this imprecision leads to substantial attenuation of disease-exposure associations, such that relative risk, dose response, and the extent to which there are thresholds in disease-exposure associations can be seriously underestimated. Linking disease-specific relative risks, especially when derived from different studies with different methods of assessing exposure, is made increasingly difficult. The most critical tasks for lessening bias in these epidemiologic descriptors are first, to lessen imprecision in measuring exposures, and second, to adjust association estimates for attenuation due to measurement imprecision.