Invited commentary: Fewell and colleagues--fuel for debate.

Concern over the impact of flawed measurement continues to nag epidemiology. Early studies indicated that the impact of measurement error is benign, leading generally only to attenuation of associations; more recent research has documented that this impact, especially within the setting of multivariate modeling, cannot be expected always to be benign. It can, for example, be a source of unsettling inconsistency. Fewell and colleagues (Am J Epidemiol 2007;166:646-655) show that residual confounding is especially persistent in the presence of multivariate confounding.