Structure of Dietary Measurement Error: Results of the OPEN Biomarker Study

TLDR

Multiple‑day food records or 24‑hour recalls are routinely used as reference instruments to calibrate food frequency questionnaires and adjust for measurement error, but this requires that their errors be independent of those in the FFQ and of true intake. The OPEN Study (Sept 1999–Mar 2000) collected doubly labeled water, urinary nitrogen, FFQ, and 24‑hour recall data from 484 healthy volunteers in Montgomery County, Maryland. When calibrated with biomarkers, the FFQ produced severe attenuation of disease relative risks for protein or energy intake (a true RR = 2 appears as ≤1.1), energy adjustment lessens this (≈1.3), and using the 24‑hour recall underestimates attenuation by up to 60 %, indicating that FFQ‑based diet‑disease findings should be re‑evaluated.

Abstract

Multiple-day food records or 24-hour dietary recalls (24HRs) are commonly used as "reference" instruments to calibrate food frequency questionnaires (FFQs) and to adjust findings from nutritional epidemiologic studies for measurement error. Correct adjustment requires that the errors in the adopted reference instrument be independent of those in the FFQ and of true intake. The authors report data from the Observing Protein and Energy Nutrition (OPEN) Study, conducted from September 1999 to March 2000, in which valid reference biomarkers for energy (doubly labeled water) and protein (urinary nitrogen), together with a FFQ and 24HR, were observed in 484 healthy volunteers from Montgomery County, Maryland. Accounting for the reference biomarkers, the data suggest that the FFQ leads to severe attenuation in estimated disease relative risks for absolute protein or energy intake (a true relative risk of 2 would appear as 1.1 or smaller). For protein adjusted for energy intake by using either nutrient density or nutrient residuals, the attenuation is less severe (a relative risk of 2 would appear as approximately 1.3), lending weight to the use of energy adjustment. Using the 24HR as a reference instrument can seriously underestimate true attenuation (up to 60% for energy-adjusted protein). Results suggest that the interpretation of findings from FFQ-based epidemiologic studies of diet-disease associations needs to be reevaluated.