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Folic Acid Advisories A Public Health Challenge? -Discussion
Daniel Herrera, Fabrice Etilé
To cite this version:
Daniel Herrera, Fabrice Etilé. Folic Acid Advisories - A Public Health Challenge? - Discussion. European Workshop of Health Economics and Econometrics, Sep 2015, Paris, France. 15 p. �hal-01602176�
Folic acid advisories,
a public health challenge?
Daniel Herrera-Araujo
(Toulouse School of
Economics/INRA)
Discussion by Fabrice Etilé
Folic acid advisories,
a public health challenge?
Daniel Herrera-Araujo
(Paris School of
Economics/Hospinnomics)
Discussion by Fabrice Etilé
Research question & context
•
Evaluation of an information
campaign aiming at increasing folic
acid intake in pregnant women
, in
order to lower the risk of Neural
Tube Defects in newborns.
–
NTDs: about 1/1000 births.
–
Lifetime cost to society: about 600,000
US$ in 2002 (CDC, Yi et al., EurJPed,
2011); 242,948 Eur in 2005
(Netherlands, Jentink et al.,
EurJPubHealth, 2008).
–
NTDs can be easily prevented by a
balanced diet and/or supplementation
during the first months of pregnancy.
•
Information campaign in France
–
Since the 1990s, raising awareness
about the need to promote the
consumption of folic acid un order to
prevent NTD.
–
April 2005:
First information campaign by
INPES (the institute in charge of health
education): leaflets, website, advices for
health care.
–
Since then, information campaign every
The 2005 campaign
•For healthcare
professionals:
–Information released in
professional reviews.
–E-mailing to 28,400 GPs
and 1142 gynaecologists.
–Website
•
For all women aged
15-45: impression of leaflets
that professionals can
give to their patients.
Research question & context
•
What has been the impact of this campaign on folic acid
intakes?
–
Debate on the cost-effectiveness of such policy as
compared to food fortification actions:
• Obeid et al. (2015, Brth Defects Research), “Between years 2000
through 2010, a total of 7478 pregnancies with spina bifida and
anencephaly out of approximately nine million births were caused by failure of European governements to introduce folic adic fortification on a population level”.
• Folic acid fortification would be cost saving if enrichment costs less
than 20,000 Euro/QALY.
• But possible side effects at high doses: no systematic policy of flour
fortification in France; some products are enriched in folic acid by manufacturers (e.g. breakfast cereals).
–
Methodological challenge of evaluating a public health
Method
•
Main challenge: the “control group”
–
Most often no control group for the evaluation of information
campaigns: before-after comparison and identification of a
discontinuity in levels or trends, holding everything else
constant => credibility?
–
Here, only women who are going to have a baby are
supposed to “take” the treatment: the other women form a
“natural” control group...
• except that some of them may also “take” the recommendation:
always-takers in the control group.
• (Fuzzy) DiD design in a reduced form approach + structural
Application
•
Data & outcomes:
–
Home scan data Kantar WorldPanel 2003-2008:
• nationally representative sample of households followed over four
years on average.
• Very exhaustive information on purchases for food-at-home
• Only households with women meal planners are kept.
• Conversion in terms of nutrient intakes, using conversion matrices
(CIQUAL) and an aggregation of products into 352 categories
–
Outcomes of interest:
• Reduced-form approach: Quarter aggregation => average daily folic
acid availability in a quarter by unit of ???? (“USDA adult equivalence scale” => adjustment for calorie needs?).
• Structural approach: demand-system estimate (food in nine
Results (1)
•
Reduced-form approach:
–
Treatment group Ti,t=1: if newborn at t or t+1.
–
zi,t: folic acid intakes
z
i t,=
α
T
i t,+ +
δ λ
t(
T
i t,×
1
{ 2004}t>)
+
controls
•
Positive & significant impact of the campaign for
women without a college degree and/or having their
first child.
–
need to control for treatment*college, policy*college etc.. In
Discussion (1)
•
Validity of the common trend assumption?
–
DID Placebo analysis with policy in 2004 => not significant;
–Use of quaterly data for households who had a child: no
impact on folic acid availability around the date of
conception before 2005...
–
Is the common trend assumption valid for all types of
households? well-educated ones, those that already had a
baby etc...
•
(SUTVA? No interactions between the control and
treatment groups? And between the treated (e.g.
informal discussions between pregnant women)?
Robustness check?)
•
Long-term impact via changes in food habits, social
Discussion (2)
•
Fuzzy DiD design:
–
Not all targeted people actually get informed (D=1)
–D≠Treat*Time
• De Chaisemartin and D’Hautfeuilles (2014)
•
The estimated DID is a lower bound of the ATT of
interest iff:
–
The ATT does not vary with actual treatment or assignment
(homogeneity?).
–
Before the policy (Time=0), the proportion of “always-takers”
(Informed: D=1) is lower in the control group (Treat=0) than
in the treatment group.
–
Information increases more in the treatment group than in
the control group.
Treat =0 Treat =1 Uninformed(D=0)
Being informed
Discussion (3)
•
Matching DiD?
–
Table 1 suggests that there are important differences
between treatment and control, and between treatment
before and treatment after (e.g. College): Heckman,
Ichimura and Todd (1997).
•
Other controls: seasonal effects (births do not occur
randomly in the year).
•
No impact on well-educated because they already had
well-balanced diets: implication in terms of
equity/inequality?
Results (2)
•
Structural approach:
–
A utility function that includes nutrient intakes
–
No prices?
–
Identification of a change in preferences (DiD for β) by
using exogenous shocks on sijct
• Interpretation of the +0.2 in terms of WTP for risk reduction (VSL: 17
Discussion (3)
•
Validity of the identification strategy... or the threat of
“Industrial Disorganization”
–
Not me: Angrist & Pischke (JEconPers, 2010).
–
Strong parametric assumptions on consumer preferences
–IV for instrumenting sijct?
• Identify a group of households with the same purchase behaviour
for food group j: those visiting mostly the same retailer the same day as household i for their purchases on j.
• For each j, compute the average nutrient content in c of all of the
products that have been purchased at lest once by a household in the reference group.
• Then compute the average “reference” share of j for its contribution
to intakes of nutrient c
Discussion (4)
•
Validity of the identification strategy...
–
IVs:
• Standard problem of social interactions, with unobserved similarities
between the household and households in its reference group.
• Source of exogenous variation? Day-to-day variations in the
reference group & the choice set produced by inter-area variations in Sunday opening rules: you should state it more clearly and
provide more evidence on it (large F-value...).
• No control for day fixed-effects?
–
