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Assessing dietary intakes in food environment research: Implications for policy and practice
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Transcript of Assessing dietary intakes in food environment research: Implications for policy and practice
Assessing dietary intakes in food environment research:
Implications for policy and practice
SHARON KIRKPATRICK University of Waterloo
JILL REEDY, KEVIN DODD, AMY SUBAR, FRAN THOMPSON, ROBIN MCKINNONUS National Cancer Institute
EBONEÉ BUTLER University of North Carolina at Chapel Hill
Assessing dietary outcomes in food environment research
Food environmen
tDiet
Body weight and other
risk factors
Incidence of chronic diseases
The food environment, diet and health
Assessing dietary outcomes in food environment research
The food environment, diet and health
Lytle L, AJPM 2009
Assessing dietary outcomes in food environment research
Recent reviews highlight a lack of consensus in the existing literature
Assessing dietary outcomes in food environment research
► Context
► Measures of the food environment: Capturing different aspects, e.g., density or distance to a
particular type of food outlet, variety and quality of in-store offerings, perceived availability of food in a particular area
Error
► Measures of dietary intake: Capturing different aspects, e.g., whole diet versus particular
foods or food groups Error
What might account for inconsistencies in the evidence?
Assessing dietary outcomes in food environment research
► Context
► Measures of the food environment: Capturing different aspects, e.g., density or distance to a
particular type of food outlet, variety and quality of in-store offerings, perceived availability of food in a particular area
Error
► Measures of dietary intake: Capturing different aspects, e.g., whole diet versus
particular aspects of diet Error
What might account for inconsistencies in the evidence?
Assessing dietary outcomes in food environment research
► Widely recognized that data collected using self-report dietary instruments contain substantial bias
► Bias can: Mask relationships that actually exist Result in spurious effects
− Particularly problematic if differential error among populations (e.g., low versus high income)
Reduce statistical power
Measuring dietary outcomes in food environment research
Barrier to policy and program interventions
Assessing dietary outcomes in food environment research
Methods for assessing diet
Recall or record Food frequency questionnaire
Brief instrument(screener)
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Bias
Number of dietary factors
Distribution of dietary factors
Time
[Money]
Assessing dietary outcomes in food environment research
Methods for assessing diet
► 24 hour recalls and food records
► Food frequency questionnaires
Assessing dietary outcomes in food environment research
► Brief instruments focused on ‘indicator foods’ (e.g., fruits, vegetables, salty or sugary snacks) Screeners or checklists
1 or 2 questions (e.g., how many servings of fruit/vegetables do you usually eat each day?)
Methods for assessing diet
Assessing dietary outcomes in food environment research
► What is the state of food environment research in terms of assessment of dietary outcomes?
► Review of peer-reviewed literature published from January 2007 through June 2012 Food environments include food stores, restaurants, schools,
home, farmers’ markets, recreational facilities, etc.
Research question and method
Kirkpatrick et al., AJPM, 2014
Assessing dietary outcomes in food environment research
► Systematic search Search engines:
− PubMed, SCOPUS, PsycInfo, Web of Science Search terms:
− [Food or nutrition or diet] AND [environment or community or neighborhood or neighbourhood] AND [measure] AND [assess]
− Food environment
► Measures of the Food Environment web compilation (appliedresearch.cancer.gov/mfe)
► Literature cited by each article
Search strategy
Assessing dietary outcomes in food environment research
2450 unique articles identified and screened
368 abstracts reviewed to assess eligibility
149 full-text articles assessed for eligibility
51 articles included in systematic review
2082 articles excluded after initial screen
219 articles excluded after review of abstracts
111 articles excluded after full-text review
13 additional articles identified via the reference lists of included articles and relevant reviews and the Measures of the Food Environment website
38 eligible articles identified
Assessing dietary outcomes in food environment research
24-hour recall
Record/Diary
FFQ Screener 2 items 1 item0
5
10
15
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35
40
% o
f arti
cles
Dietary assessment in food environment research (n=51)
Assessing dietary outcomes in food environment research
24-hour recall
Record/Diary
Food frequency questionnaire Screener Two Items Single Item
Fruit and/or Vegetables (n=35)
Sugar-sweetened beverages(n=14)
Fast Food(n=9)
Diet Quality(n=9)
Note:- The count of instruments exceeds the number of studies reviewed because one or more studies used multiple instruments.- The outcomes included are those most commonly examined among the studies reviewed. Note that a single study may include multiple outcomes and so the sum of studies examining unique outcomes exceeds the total number of studies reviewed.
Dietary assessment in food environment research (n=51)
Assessing dietary outcomes in food environment research
► Tendency toward the use of brief (more error-prone) assessment instruments Low cost and respondent burden Results in focus on ‘indicator foods’ (or due to a priori
interest in specific food groups?)
Dietary assessment in food environment research (n=51)
Assessing dietary outcomes in food environment research
► Existence of bias in dietary data and the potential implications for study results rarely discussed
► In several papers, it was noted that the dietary assessment tool was ‘validated’ Validity often assessed by comparing the instrument to
another self-report instrument limited utility
Dietary assessment in food environment research (n=51)
Assessing dietary outcomes in food environment research
► Relationships between food environment features and dietary outcomes more consistent in studies using less error-prone measures
Dietary assessment in food environment research (n=51)
Studies with 24HR, diaries, FFQ
• 76% showed overall effects in the expected direction
Studies with screeners, 1-2 items
• 55% showed overall effects in the expected direction
Assessing dietary outcomes in food environment research
► Explosion of research examining relationships between features of food environments and dietary intakes
► Bias in dietary data may be substantial, particularly if estimates are based on brief dietary instruments May lead to spurious effects and reduced statistical power to
detect associations
► Barrier to establishing policy and program interventions to improve diet and health
Conclusions
Assessing dietary outcomes in food environment research
► Effects of bias when diet is the outcome (rather than an exposure) not thoroughly examined – need more research to inform strategies
► In the meantime? Start with the best instrument possible: technologic
advances allow collection of more detailed and less biased dietary data
Use available strategies to reduce the effects of error (e.g., calibrate data from brief instruments using other sources)
Discuss potential implications of bias on study results and inconsistencies with other studies
Moving forward