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Open Access Research

Assessing validity of a short food frequency questionnaire on present dietary intake of elderly Icelanders

Tinna Eysteinsdottir13*, Inga Thorsdottir12, Ingibjorg Gunnarsdottir12 and Laufey Steingrimsdottir12

Author Affiliations

1 Unit for Nutrition Research, University of Iceland and Landspitali National-University Hospital, Reykjavik, Iceland

2 Faculty of Food Science and Human Nutrition, School of Health Sciences, University of Iceland, Reykjavik, Iceland

3 Unit for Nutrition Research, Landspitali-University Hospital, Eiriksgata 29, IS-101 Reykjavik, Iceland

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Nutrition Journal 2012, 11:12  doi:10.1186/1475-2891-11-12

Published: 13 March 2012

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.

Method

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.

Result

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.

Conclusion

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.

Keywords:
Food frequency questionnaire; Validity; Elderly; Nutrition