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- Wolk, A, et al.
(author)
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Self-administered food frequency questionnaire : the effect of different designs on food and nutrient intake estimates
- 1994
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In: International Journal of Epidemiology. - : Oxford University Press (OUP). - 0300-5771 .- 1464-3685. ; 23:3, s. 570-6
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Journal article (peer-reviewed)abstract
- BACKGROUND: Our objective was to determine the possible influence that different designs of a food frequency questionnaire might have on food, energy and nutrient intake estimates.METHODS: A population-based survey included 6783 women, 40-70 years old, living in central Sweden. Using a factorial study design, we compared eight different types of questionnaire covering combinations of three factors: increasing/decreasing frequency categories; addition of portion sizes; and addition of non-dietary questions. All questionnaires included the same list of 60 food items. One of the eight questionnaires was mailed to each subject according to a random assignment. The overall response rate was 77%.RESULTS: Compared with increasing frequencies, decreasing order of frequency categories entailed 3-11% higher estimates of mean intake for 7 of 14 food groups, 4% higher estimates for energy and 3-6% higher estimates for 13 of 18 nutrients. Addition of portion sizes had heterogeneous effects, both on dietary items (e.g. from -30% decrease for eggs to +76% increase for coffee) and on calculated nutrients (from -7% for beta-carotene to +19% for vitamin C). The inclusion of some additional non-dietary questions did not influence the estimated mean intake of any food or nutrient.CONCLUSIONS: The results of this study have implications for the design of questionnaires and for pooled analyses in nutritional epidemiology, when different food questionnaires are used.
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| 2. |
- Kuskowska-Wolk, A, et al.
(author)
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Effects of different designs and extension of a food frequency questionnaire on response rate, completeness of data and food frequency responses
- 1992
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In: International Journal of Epidemiology. - : Oxford University Press (OUP). - 0300-5771 .- 1464-3685. ; 21:6, s. 1144-50
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Journal article (peer-reviewed)abstract
- The authors studied how the introduction of several modifications to a basic food frequency questionnaire can influence the results of dietary surveys. Modifications covered eight combinations based on three levels: increasing versus decreasing order of frequency categories; questionnaires without versus with questions about portion sizes, and questionnaires without versus with extra non-dietary questions. The sample included 6783 women between the ages of 40 and 70 years who took part in mammography screening. The women were randomly assigned to one of the eight study groups. All of the women in each group received one of the eight differently modified questionnaires. The forms extended in length by extra non-dietary questions and portion size categories resulted in a 20% higher total non-response compared to the shorter basic form. Partial non-response was significantly lower for all four questionnaire types that included portion sizes. When portion sizes were included in the questionnaire, the reported mean frequency of consumption was significantly reduced for fat (-10 times per month), milk (-6), bread (-5), vegetables (-2) and fish (-0.4). The decreasing order of responses to the frequency categories was associated with a statistically significant increase in the frequency responses for bread (2.6 times per month), vegetables (2) and fish (0.6). These data provide evidence that the design and extension of food frequency questionnaires influence the results of dietary studies.
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