title: Assessing validity of a short food frequency questionnaire on present dietary intake of elderly Icelanders.
abstract: BACKGROUND
  Few studies exist on the validity of food frequency questionnaires (FFQs) administered to elderly people. The aim of this study was to assess the validity of a short FFQ on present dietary intake, developed specially for the AGES-Reykjavik Study, which includes 5,764 elderly individuals. Assessing the validity of FFQs is essential before they are used in studies on diet-related disease risk and health outcomes.
  
  
  METHODS
  128 healthy elderly participants (74 y ± 5.7; 58.6% female) answered the AGES-FFQ, and subsequently filled out a 3-day weighed food record. Validity of the AGES-FFQ was assessed by comparing its answers to the dietary data obtained from the weighed food records, using Spearman's rank correlation, Chi-Square/Kendall's tau, and a Jonckheere-Terpstra test for trend.
  
  
  RESULTS
  For men a correlation ≥ 0.4 was found for potatoes, fresh fruits, oatmeal/muesli, cakes/cookies, candy, dairy products, milk, pure fruit juice, cod liver oil, coffee, tea and sugar in coffee/tea (r = 0.40-0.71). A lower, but acceptable, correlation was also found for raw vegetables (r = 0.33). The highest correlation for women was found for consumption of rye bread, oatmeal/muesli, raw vegetables, candy, dairy products, milk, pure fruit juice, cod liver oil, coffee and tea (r = 0.40-0.61). An acceptable correlation was also found for fish topping/salad, fresh fruit, blood/liver sausage, whole-wheat bread, and sugar in coffee/tea (r = 0.28-0.37). Questions on meat/fish meals, cooked vegetables and soft drinks did not show a significant correlation to the reference method. Pearson Chi-Square and Kendall's tau showed similar results, as did the Jonckheere-Terpstra trend test.
  
  
  CONCLUSIONS
  A majority of the questions in the AGES-FFQ had an acceptable correlation and may be used to rank individuals according to their level of intake of several important foods/food groups. The AGES-FFQ on present diet may therefore be used to study the relationship between consumption of several specific foods/food groups and various health-related endpoints gathered in the AGES-Reykjavik Study.
authors.affiliation: Unit for Nutrition Research, University of Iceland and Landspitali National-University Hospital, Reykjavik, Iceland. tinnaey@landspitali.is
authors.forename: Tinna
authors.initials: T
authors.lastname: Eysteinsdottir
authors.forename: Inga
authors.initials: I
authors.lastname: Thorsdottir
authors.forename: Ingibjorg
authors.initials: I
authors.lastname: Gunnarsdottir
authors.forename: Laufey
authors.initials: L
authors.lastname: Steingrimsdottir
mesh_terms: D000368:Aged; D000818:Animals; D003060:Cod Liver Oil; D003069:Coffee; D003611:Dairy Products; D004032:Diet / Q000706:statistics & numerical data; D015930:Diet Records; D004034:Diet Surveys; D002149:Energy Intake; D005247:Feeding Behavior; D005260:Female; D005638:Fruit; D015577:Geriatric Assessment; D006801:Humans; D007055:Iceland; D007407:Interviews as Topic; D008297:Male; D008460:Meat; D015596:Nutrition Assessment; D012737:Sex Factors; D011795:Surveys and Questionnaires / Q000592:standards*; D013662:Tea; D014675:Vegetables
chemical_list: D003069:Coffee; D013662:Tea; D003060:Cod Liver Oil