title: Cognitive research enhances accuracy of food frequency questionnaire reports: results of an experimental validation study.
abstract: OBJECTIVE
  To test whether changing a food frequency questionnaire (FFQ) on the basis of cognitive theory and testing results in greater accuracy. Accuracy was examined for 4 design issues: a) Grouping: asking about foods in a single vs multiple separate questions; b) different forms of a food: asking consumption frequency of each form of a food (eg, skim, 2%, whole milk) vs a nesting approach--asking frequency of the main food (eg, milk) and proportion of times each form was consumed; c) additions (eg, sugar to coffee): asking independent of the main food vs nested under the main foods; d) units: asking frequency and portion size vs frequency of units (eg, cups of coffee).
  
  
  METHODS
  Participants in two randomly assigned groups completed 30 consecutive daily food reports (DFRs), followed by 1 of 2 FFQs that asked about foods consumed in the past month. One was a new, cognitively-based National Cancer Institute (NCI) Diet History Questionnaire; the other was the 1992 NCI-Block Health Habits and History Questionnaire.
  
  
  METHODS
  623 participants, age range 25 to 70 years, from metropolitan Washington, DC. Statistical analyses performed Accuracy was assessed by comparing DFR and FFQ responses using categorical (percent agreement) and continuous (rank order correlation, discrepancy scores) agreement statistics.
  
  
  RESULTS
  Grouping: accuracy was greater using separate questions. Different forms of food: accuracy was greater using nesting. Additions: neither approach was consistently superior; accuracy of the addition report was affected by accuracy of the main food report. Units: both approaches were similarly accurate.
  
  
  CONCLUSIONS
  Accuracy of FFQ reporting can be improved by restructuring questions based on cognitive theory and testing.
authors.affiliation: Division of Cancer Control and Population Sciences, National Cancer Institute, Bethesda, MD 20892-7344, USA. tompsof@mail.nih.gov
authors.forename: Frances E
authors.initials: FE
authors.lastname: Thompson
authors.forename: Amy F
authors.initials: AF
authors.lastname: Subar
authors.forename: Charles C
authors.initials: CC
authors.lastname: Brown
authors.forename: Albert F
authors.initials: AF
authors.lastname: Smith
authors.forename: Carolyn O
authors.initials: CO
authors.lastname: Sharbaugh
authors.forename: Jared B
authors.initials: JB
authors.lastname: Jobe
authors.forename: Beth
authors.initials: B
authors.lastname: Mittl
authors.forename: James T
authors.initials: JT
authors.lastname: Gibson
authors.forename: Regina G
authors.initials: RG
authors.lastname: Ziegler
mesh_terms: D000328:Adult; D000368:Aged; D003071:Cognition; D015930:Diet Records; D004034:Diet Surveys; D005247:Feeding Behavior; D005260:Female; D005502:Food / Q000145:classification; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires / Q000592:standards*