Structure of dietary measurement error: results of the OPEN biomarker study.
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.
Kipnis
Victor
V
Biometry Research Group, Division of Cancer Prevention, National Cancer Institute, Bethesda, MD 20892-7354, USA. victor_knipis@nih.gov
Subar
Amy F
AF
Midthune
Douglas
D
Freedman
Laurence S
LS
Ballard-Barbash
Rachel
R
Troiano
Richard P
RP
Bingham
Sheila
S
Schoeller
Dale A
DA
Schatzkin
Arthur
A
Carroll
Raymond J
RJ
D000328:Adult; D000368:Aged; D015982:Bias; D015415:Biomarkers / Q000652:urine; D017666:Deuterium Oxide / Q000652:urine; D004032:Diet; D004034:Diet Surveys; D004044:Dietary Proteins / Q000008:administration & dosage*; D002149:Energy Intake; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D008396:Maryland / Q000453:epidemiology; D008875:Middle Aged; D015233:Models, Statistical; D012015:Reference Standards; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards*; D014508:Urea / Q000652:urine
D015415:Biomarkers; D004044:Dietary Proteins; D014508:Urea; D017666:Deuterium Oxide