Dissecton of a Research Project
Vicken Y. Totten MD
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Scholarly Work
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Of publishable quality
Many undergrad programs require a thesis
Most Masters programs
All PhD programs
Some MD / DO programs
All EM residencies.
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General Outline
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Idea
Look it up, who has done what, refine idea
Background search, lit review (publishable)
Formulate study, protocol, IRB (if necessary)
Actually gather the data
Analyze and present the data
Graduate and / or publish the study.
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Idea
• Lots of obese people in Cleveland
• Plain Dealer -> talks about “food deserts”
• Fruits and vegetables intake inversely
proportional to obesity
• Other studies show that it is hard for the poor
to access food
• Brainstorming -> what are factors in “access”?
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Access
• Questions for the respondent
– Can you get there?
– Can you afford it?
– Is it worth buying?
• For the researcher
– Where can I access such a population?
– How can I get them to answer?
– How much time and effort can I afford to spend?
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Measuring Access To Fresh
Produce In An Urban
Midwestern City
Apoorva K. Chandar, MBBS
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The parts of a study
• Goal = what change in the world?
• Objectives = what can I achieve in this
study?
• Background = why does this matter?
Who’s done what before?
• Significance = Who cares?
• Method = HOW will I get this done?
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Purpose = Goal
To measure access to fresh produce (fruits
and vegetables) in an Urban Midwestern
City using a novel survey instrument
Availability
Access
Affordability
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Objectives = the specific
achievables in this particular study
• Identify socio-demographic factors associated with
affordability and availability of fresh produce
• Describe the associations between detailed and
overall (composite) measures of availability and
affordability of fresh produce
• Assess how accurately NHANES questions capture
affordability and availability of fresh produce
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Timeline (Gotta plan ahead. It will always
take twice as long as you expected.)
2010
2011
2012
• Summer Internship and Conceptual model
• Identification of interest area within the conceptual model
• More brainstorming
• Designing and finalizing the Survey instrument
• IRB Approval
• Data collection, data entry and analysis
Capstone Presentation
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Background
• Fruits and vegetables form an integral part of a healthy diet
• Provide essential vitamins and minerals; excellent sources of
fiber
• Studies have linked fruit and vegetable consumption to lower
rates of obesity, heart disease, diseases of aging and cancer
• 2010 US Dietary guidelines recommend that
Americans get at least 2½ cups of fruits and
vegetables per day
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Background, continued
• Only 33% of adults meet the fruit consumption target and only 27%
eat the recommended amount of vegetables in the US
• Access to healthy food has been shown to be related to availability
and affordability
• Low income neighborhoods are more likely to have a large number
of convenience stores and smaller grocery stores-these stores do
not carry a good variety of fruits of vegetables
• When they do have fruits and vegetables, they are often of lower
quality and are sold at a higher price when compared to
supermarkets
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Public Health Significance
aka, “who cares?”
• Disparities in access to healthy food, particularly fresh, high
quality fruits and vegetables
• Burden of illness due to chronic diseases like diabetes, heart
disease and cancer is enormous
• It is necessary to meet the Healthy People 2020 goals with
regard to increasing fruit and vegetable consumption
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Significance / Relevance
to Cleveland
• In the city of Cleveland alone, more than 55% of the people
live in food desert areas
• Urban sprawl and flight of supermarkets to the suburbs have
contributed to the “expansion” of these food deserts
• “Understanding the availability of fresh food from yearround food sources such as supermarkets and larger grocery
stores is one facet of addressing food security among lower
income residents” - Cuyahoga County Assessment: Access to
Supermarkets (December 2011)
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Design your study
• What do you want to know? (objective)
• What do you think will predict it?
– Predictive variables
• How will you know if you now have the
answer?
– Outcome variables
• What else might factor in?
– Confounding variables
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Variables
• List your variables: predictor, outcome
and confounders
• Describe your variables: how do you want
the data? Continuous, discrete, ordinal…
• Define your variables / terms carefully
• Decide how you will analyze those
variables: what statistical tests will answer
your question.
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Detailed Availability measures predicting Overall Availability
Analytic method
Multiple Linear Regression
Outcome variable Overall Availability
Study variables
Continuous
Variety
Continuous
Quality
Continuous
Ease of Access
Continuous
Place of Purchase
Dichotomous
Number
Continuous
Time
Continuous
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Key terminology
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Availability: Availability concerns whether foods of interest (fruits and vegetables) are
present in an environment (Cullen et al., 2003)
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Affordability: refers to the idea that low-income groups must choose foods based on
their price, not just relative to other foods but relative to competing necessities, such
as housing, clothing, and transportation (Ver Ploeg et al., 2009)
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Supermarket: > 25,000 square feet, self-service, carries at least 11 varieties of both
fruits and vegetables
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Large Grocery Store: < 25,000 square feet, carries at least 6 different varieties of both
fruits and vegetables
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Small Grocery Store: fewer departments, carries at least 2 varieties of fruits and
vegetables
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Farmer’s Market: A public market place where fresh foods from a defined local area
are sold by the people who have grown, gathered, raised or caught them
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Convenience Store: stocks shelf stable foods such as bread, soda and snacks and a
limited selection of fresh fruits and vegetables, if any
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Methods
• This is a description of how you plan to carry
out your study.
• It should be written so that another intelligent
person could carry it out without asking you
anything, and get the same results.
• Often written very formally (in a particular
format)
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This study
• Survey – best to use one already validated
• Validity of surveys includes face validity, use
validity, internal and external validities
• If you create your own, should describe how
you chose the items you chose, and why.
• Chandar chose to write his own, use NHANES questions. His
paper-based surveys-took about 7 minutes to complete
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Survey Instrument
• 35 item survey - Consisted of overall and detailed measures of
Availability and Affordability of fresh produce
• Also contained questions about sociodemographics (Age,
Race, Gender, Education, Marital status, Income, Employment
status and Enrollment in Supplemental Nutrition Assistance
Program [SNAP])
• NHANES (National Health and Nutrition Examination Survey)
questions on Availability and Affordability were included
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Availability measures
Fruits and vegetables are easily available for
purchase
1----------------------------5
1 - Strongly Disagree
5 - Strongly Agree
1. Variety
The variety of fruits and vegetables is limited
at the shop where I buy them
1----------------------------5
1 - Strongly Disagree
5 - Strongly Agree
2. Quality
Fruits and vegetables are of high quality at
the place where I shop for them
1----------------------------5
1 - Strongly Disagree
5 - Strongly Agree
3. Ease of Access
How easy is it for you to get to the grocery
store?
1----------------------------5
1 - Very Difficult
5 - Very Easy
4. Place of Purchase
Where do you primarily shop for fruits and
vegetables?
1. Supermarket
2. Small Grocery Store
3. Convenience Store
4. Farmer’s Market
5. Number
How many grocery stores selling fruits and
vegetables are close to where you live?
Continuous variable
Overall/Composite
measure
Detailed measures
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Affordability measures
Fruits and vegetables are affordable to me
1----------------------------5
1 - Strongly Disagree
5 - Strongly Agree
1. Purchasing capacity
I can afford to buy fruits and vegetables each
time I go to the grocery store
1----------------------------5
1 - Strongly Disagree
5 - Strongly Agree
2. Quantity
I can’t afford to buy enough fruits and
vegetables
1----------------------------5
1 - Strongly Disagree
5 - Strongly Agree
3. Eating healthy
Lack of money prevents me from eating
healthier
1----------------------------5
1 - Strongly Disagree
5 - Strongly Agree
Overall/Composite
measure
Detailed measures
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NHANES Questions
Availability
How much time does it take for you to get to the
grocery store (in minutes)?
Continuous variable
1. Price factor
When you buy fruits and vegetables from a grocery
store, how important is “price”?
1----------------------------4
1 - Not at all important
4 - Very important
2. Organic fruits
and vegetables
In the past 30 days, when you bought fruits or
vegetables, how often did you buy organic fruits and
vegetables?
1----------------------------5
1 - Never
5 - Always
Time
Affordability
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Methods: Data Collection
• Site: Emergency Department (ED) of University Hospitals of
Cleveland
• ED of University Hospitals gets over 30000 patients per year –
predominantly Black neighborhoods of Hough-Norwood,
poorer parts of East side of Cleveland
• Convenience sample: 300 surveys
• PI and trained EMRD Research Assistants collected the surveys
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Methods: Data Collection
• Surveys were handed out to any willing
participant over the age of 18
• Surveys were collected in the ED patient
rooms and waiting areas
• People could take the survey only if they did
grocery shopping for themselves or their
household
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Methods: Data Entry and Analysis
• Data was entered and stored in REDCap
• Analysis was done using IBM SPSS v.20
• Descriptive statistics, tests of association,
correlations and regression analysis
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Statistics
• The type of variables you chose determine
which statistical analysis you will use.
• The computing power available to you may
determine what type of variable you will
gather.
• In your first draft, boilerplate statistics
may be used, but for your own purposes
are not enough.
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Results
• Before you run your statistics, decide what is
“significant” and to whom.
• In a large enough study, 1 person of 10,000
difference can be statistically significant, but
not clinically significant.
• “p-values” are inadequate. NNT / NNH and
costs are of greater importance clinically.
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Description
• The first part of your results is to describe
your population. Others will want to know
how similar are their populations, and the
population itself determines many of the
confounders.
• Confounders are also part of limitations
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Descriptive: Demographics
Table 1 (N = 300)
Demographic characteristics and associations with overall Availability and Affordability
Age
18 to 34
35 to 54
55 to 64
Above 65
N (%)
141 (47.2)
104 (34.8)
36 (12.0)
18 (6.0)
Availability (p-value)
0.04
Affordability (p-value)
0.11
Gender
Male
Female
61 (20.6)
235 (79.4)
0.38
0.26
Race
White
Black
Other
48 (16.2)
225 (75.8)
24 (8.1)
0.25
0.58
Education
Less than High School
High School Graduate
Some College
Bachelor/Graduate/Professional
24 (8.0)
98 (32.8)
130 (43.5)
47 (15.7)
0.88
0.28
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Descriptive: Demographics
Table 1 (N = 300)
Demographic characteristics and associations with overall Availability and Affordability
Marital Status
N (%)
Married/Widowed
90 (30.4)
Divorced/Separated
45 (15.2)
Never Married
161 (54.4)
Availability (p-value)
Affordability (p-value)
0.09
0.13
0.37
0.22
0.59
0.75
Employment Status
Employed
141 (49.5)
Unemployed
84 (29.5)
Student/ Retired
60 (21.1)
Enrollment in SNAP
Yes
137 (46.3)
No
159 (53.7)
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Descriptive: Demographics
Table 1 (N = 300)
Demographic characteristics and associations with overall Availability and Affordability
Means (SD)
Number of People in Household
3.1
Availability (pvalue)
Affordability (pvalue)
0.44
0.10
0.36
0.29
(1.60)
Income
33346.94
(28317.25)
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Availability and Affordability
“simple descriptive statistics”
Table 2 (N = 300)
Means and Standard Deviations for overall and detailed measures of Availability
and Affordability
Availability
M
SD
Overall availability
4.03
1.14
Variety
2.46
1.30
Quality
3.72
1.10
Ease of Access
4.01
1.02
Number of grocery stores
2.30
0.83
M
SD
Overall affordability
3.55
1.20
Purchasing capacity
3.47
1.22
Quantity
2.41
1.22
Eating Healthy
2.65
1.35
Affordability
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Descriptive: NHANES
Table 3 (N = 300)
Means and Standard Deviations for NHANES questions on Availability and
Affordability
Availability
Time
M
24.09
SD
19.55
Affordability
M
SD
Price Factor
3.56
0.76
Organic fruits and vegetables
1.91
1.11
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Statistical Analysis
• After the first “simple descriptive
statistics” come the comparisons
• Relationships and comparisons
• Relationships do not prove causality,
(causality care rarely be ‘proven’) but
increasingly frequent association suggests
at least common factors.
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Regression analyses
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Regression analysis
• A technique for modeling the effects of many
predictor variables on one outcome.
• Linear regression
• Simple regression
Ordinary least squares
• Polynomial regression
• General linear model
• Generalized linear model
• Nonlinear regression
• And many more
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Sociodemographic variables predicting Overall Availability
Table 4
Summary of Multiple Regression Analysis for Sociodemographic variables predicting
Overall Availability (N=220)
Variable
β
p-value
Age Over 65
.16
.03
Enrollment in SNAP
.19
.01
Divorced/Separated
.16
.04
Note: R2 = 0.10 (p = 0.09) indicating that the model did not attain significance.
Age was recoded as 3 dummy variables with 35 – 54 serving as the reference group.
Marital status was recoded as 2 dummy variables with Married/Divorced as the
reference group.
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Sociodemographic variables predicting Overall Affordability
Table 5
Summary of Multiple Regression Analysis for Sociodemographic variables predicting
Overall Affordability (N=220)
Variable
β
p-value
18 – 35 years
.18
.03
Income
.19
.04
Divorced/Separated
.16
.01
Note: R2 = 0.11 (p = 0.07) indicating that the model was not significant.
Age was recoded as 3 dummy variables with 35 – 54 serving as the reference group.
Marital status was recoded as 2 dummy variables with Married/Divorced as the
reference group.
Income was coded as a continuous variable.
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Detailed Availability measures predicting Overall Availability
Analytic method
Multiple Linear Regression
Outcome variable Overall Availability
Study variables
Continuous
Variety
Continuous
Quality
Continuous
Ease of Access
Continuous
Place of Purchase
Dichotomous
Number
Continuous
Time
Continuous
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Detailed Availability measures predicting Overall Availability
Table 6
Summary of Multiple Regression Analysis for Detailed Availability measures predicting Overall
Availability (N=223)
Variable
Variety
Quality
Ease of Access
Place of Purchase
Number
Time
β
p-value
.08
.20
.36
.00
-.27
.00
.05
.36
.12
.04
.02
.67
Note: R2 = 0.28 (p = 0.000) indicating that 28% of the variance was explained by the model
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Detailed Affordability measures predicting Overall Affordability
Analytic method
Multiple Linear Regression
Outcome variable Overall Affordability
Continuous
Purchasing capacity
Continuous
Quantity
Continuous
Eating healthy
Continuous
Price factor
Continuous
Study variables
Organic fruits and vegetables Continuous
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Detailed Affordability measures predicting Overall Affordability
Table 7
Summary of Multiple Regression Analysis for Detailed Affordability measures predicting Overall
Affordability (N=269)
Variable
Purchasing capacity
Quantity
Eating healthy
Price factor
Organic fruits and vegetables
β
p-value
.45
.00
-.09
.12
-.10
.10
-.11
.04
-.03
.50
Note: R2 = 0.36 (p = 0.000) indicating that 36% of the variance was explained by the model
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NHANES questions predicting Overall Availability and Affordability
Availability:
• There was no association between time taken to get to the
grocery store and overall availability, r(248) = .00, p = .99
Affordability:
• Price factor was associated with overall affordability, β = -.34,
t(275) = -5.02, (p < .001)
• Price and ability to buy organic fruits or vegetables only
explained 9% of the variance in overall affordability, R2 = .09
(p < .001)
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Summary of Results
• Sociodemographics did not have a direct effect on overall availability and
affordability; effect was mediated by the detailed measures
• Quality of fresh produce, ease of access to grocery stores and number of
grocery stores close to place of residence strongly predicted overall
availability
• Time and ease of access were both included in the same model of
availability, but only ease of access predicted overall availability
• Purchasing capacity and “price” factor strongly predicted overall
affordability
• NHANES affordability model only explained 9% of the variance, whereas
our affordability model accounted for 36% of the variance indicating that
our model was better and our detailed affordability measures captured
overall affordability well
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Summary of results
• After presenting the data so that others can
see it, interpret it for them, make your point.
• Keep it brief
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Discussion
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Epstein and colleagues found that raising the price of fruits and vegetables
resulted in decreased purchases of those foods (Epstein, L. H. et al., 2006). Price
was an important factor in determining affordability in our study
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Presence of Supermarkets has been linked to fruit and vegetable consumption
(Zenk et al., 2009). In our study, type of store did not influence overall availability,
but number of grocery stores close to place of residence did
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Rose and Richards (2004) have shown that easy access to supermarkets is
associated with increased household use of fruits among SNAP beneficiaries. Ease
of access was a significant predictor of availability in our study
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Martin et al. (2012) found a positive association between fruit and vegetable
variety and perceptions of availability. In our study, variety of fresh produce
didn’t seem to influence availability
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Bodor et al. (2007) found that greater vegetable availability within 100m of
residence is associated with greater consumption. Ease of access to the nearest
grocery store was associated with overall availability
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Discussion
• This is where you get some free rein to write
about your passion. When you write the final
paper, this is where much of your background
ends up.
• The exact order of discussion / limitations /
summary / Conclusions / recommendations
(where do we go from here), depends on the
journal you want to submit to.
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Strengths and Limitations
Strengths:
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Based on a conceptual model
Independently designed survey
Addition of NHANES questions to the survey
Local Public Health relevance
Limitations:
1.
2.
3.
4.
Site of survey: ED patients
Missing values for some variables
Self-reported data
Objective food environment is not necessarily associated with
perceptions of the food environment (Williams et al., 2012)
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Conclusion and Recommendations
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Improve zoning and transportation policies to make supermarkets, grocery stores,
and farmers markets more accessible - grocery stores along bus routes, mobile
fruit and vegetable vans in strategic places
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Financial and non-financial incentives should be given to promote locally grown
produce and also for stores in impoverished neighborhoods to carry high quality
fresh produce - Cleveland Corner store project
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As affordability is related to pricing, measures should be taken to reduce the prices
of fresh produce
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Focus on policy: Fruit and Vegetable Rx program, Community transformation
grants
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Outreach and education to encourage residents of lower-income neighborhoods
and SNAP enrollees to use farmers markets
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Future NHANES surveys should expand the repertoire of questions to better
capture availability and affordability
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Future Work
• Recoding variables as dichotomous and
running logistic regressions
• Conduct the survey across a broader
sociodemographic spectrum, with a
larger sample size
• Reliability testing of the scale
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Qualitative Responses
• “Organic fruits and vegetables would be my first choice, but they are too
expensive. Even regular fruits and veggies are expensive. Neighborhood
stores offer old, bad fruits and veggies.”
• “It is extremely difficult to get decent fruits and vegetables at a good price.
Generally, they are of very poor quality as well.”
• “If fruits and vegetables were more affordable, I could have purchased
more of them. I make sure I get enough fruit for my daughters’ lunches. It
is difficult, though. Then if I can’t get to the grocery store, I can’t go to the
convenience store cause the prices are jacked up. And there are no
healthy selections to choose from.”
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Questions?
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