Crossover Designs in Nutrition and Dietetics Research.

This article is the 12th installment in a statistical series exploring the importance of research design, epidemiologic methods, and statistical analysis as applied to nutrition and dietetics research. The purpose of this series is to assist registered dietitian nutritionists in interpreting nutrition research and aid nutrition researchers in applying scientific principles to produce high-quality nutrition research. This article focuses on the use of crossover designs in nutrition and dietetics research. The purpose is to distinguish the crossover design from the randomized clinical trial, define important terms, illustrate a 2×2 crossover design, discuss potential confounding variables in the crossover design, describe the analysis and interpretation of crossover data, present sample size considerations, provide examples of the use of the crossover design in nutrition and dietetics, and discuss additional considerations when the independent variable has more than two levels.