title: Reliability and validity of food frequency questionnaire and nutrient biomarkers in elders with and without mild cognitive impairment.
abstract: BACKGROUND
  There is great interest in the nutritional strategies for the prevention of age-related cognitive decline, yet the best methods for nutritional assessment in the populations at risk for dementia are still evolving. Our study objective was to examine the reliability and validity of the 2 common nutritional assessments (plasma nutrient biomarkers and Food Frequency Questionnaire) in the people at risk for dementia.
  
  
  METHODS
  Thirty-eight elders, half with amnestic-mild cognitive impairment were recruited. Nutritional assessments were collected together at the baseline and again at 1 month. Intraclass and Pearson correlation coefficients quantified reliability and validity.
  
  
  RESULTS
  Twenty-six nutrients were examined. The reliability was very good or better for 77% (20/26, intraclass correlation coefficients or ICC ≥0.75) of the plasma nutrient biomarkers and for 88% of the food frequency questionnaires (FFQ) estimates. Twelve of the nutrient biomarkers were as reliable as the commonly measured plasma cholesterol (ICC≥0.92). FFQ and plasma long-chain fatty acids (docosahexaenoic acid, r=0.39, eicosapentaenoic acid, r=0.39) and carotenoids (α-carotene, r=0.49; lutein + zeaxanthin, r=0.48; β-carotene, r=0.43; β-cryptoxanthin, r=0.41) were correlated, but these significant correlations were present only in non-impaired elders.
  
  
  CONCLUSIONS
  The reliability and validity of the FFQ and nutrient biomarkers vary according to the nutrient of interest. Memory deficit attenuates validity and inflates reliability of FFQ reports. Many plasma nutrient biomarkers have very good reliability over 1-month, regardless of memory state. This objective method can circumvent sources of error seen in other less direct and subjective methods of nutritional assessment.
authors.affiliation: Department of Neurology, Oregon Health and Science University, Portland, OR 97239, USA. bowmang@ohsu.edu
authors.forename: Gene L
authors.initials: GL
authors.lastname: Bowman
authors.forename: Jackilen
authors.initials: J
authors.lastname: Shannon
authors.forename: Emily
authors.initials: E
authors.lastname: Ho
authors.forename: Maret G
authors.initials: MG
authors.lastname: Traber
authors.forename: Balz
authors.initials: B
authors.lastname: Frei
authors.forename: Barry S
authors.initials: BS
authors.lastname: Oken
authors.forename: Jeffery A
authors.initials: JA
authors.lastname: Kaye
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Quinn
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood*; D003072:Cognition Disorders; D004032:Diet; D005260:Female; D005502:Food; D006801:Humans; D008297:Male; D015596:Nutrition Assessment; D009752:Nutritional Status; D010865:Pilot Projects; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires
chemical_list: D015415:Biomarkers