Wolfgang Ahrens, PhD, is deputy scientific director of the Leibniz Institute for Prevention Research and Epidemiology -- BIPS in Bremen, Germany. Prof. Dr. Ahrens also is professor of epidemiological methods at the University of Bremen, Germany, and head of the Department of Epidemiological Methods and Etiological Research at BIPS.Iris Pigeot, PhD, is director of the Leibniz Institute for Prevention Research and Epidemiology -- BIPS in Bremen, Germany. Prof. Dr. Pigeot also is full professor (C4) in the Department of Mathematics and Computer Science at the University of Bremen, Germany, and head of the Department of Biometry and Data Management at BIPS.