Context While gluten ingestion is responsible for the signs and symptoms of
celiac disease, it is not known what factors are associated with initial appearance
of the disease.
Objective To examine whether the timing of gluten exposure in the infant diet
was associated with the development of celiac disease autoimmunity (CDA).
Design, Setting, and Patients Prospective observational study conducted in Denver, Colo, from 1994-2004
of 1560 children at increased risk for celiac disease or type 1 diabetes,
as defined by possession of either HLA-DR3 or DR4 alleles, or having a first-degree
relative with type 1 diabetes. The mean follow-up was 4.8 years.
Main Outcome Measure Risk of CDA defined as being positive for tissue transglutaminase (tTG)
autoantibody on 2 or more consecutive visits or being positive for tTG once
and having a positive small bowel biopsy for celiac disease, by timing of
introduction of gluten-containing foods into the diet.
Results Fifty-one children developed CDA. Findings adjusted for HLA-DR3 status
indicated that children exposed to foods containing wheat, barley, or rye
(gluten-containing foods) in the first 3 months of life (3 [6%] CDA positive
vs 40 [3%] CDA negative) had a 5-fold increased risk of CDA compared with
children exposed to gluten-containing foods at 4 to 6 months (12 [23%] CDA
positive vs 574 [38%] CDA negative) (hazard ratio [HR], 5.17; 95% confidence
interval [CI], 1.44-18.57). Children not exposed to gluten until the seventh
month or later (36 [71%] CDA positive vs 895 [59%] CDA negative) had a marginally
increased risk of CDA compared with those exposed at 4 to 6 months (HR, 1.87;
95% CI, 0.97-3.60). After restricting our case group to only the 25 CDA-positive
children who had biopsy-diagnosed celiac disease, initial exposure to wheat,
barley, or rye in the first 3 months (3 [12%] CDA positive vs 40 [3%] CDA
negative) or in the seventh month or later (19 [76%] CDA positive vs 912 [59%]
CDA negative) significantly increased risk of CDA compared with exposure at
4 to 6 months (3 [12%] CDA positive vs 583 [38%] CDA negative) (HR, 22.97;
95% CI, 4.55-115.93; P = .001; and HR,
3.98; 95% CI, 1.18-13.46; P = .04, respectively).
Conclusion Timing of introduction of gluten into the infant diet is associated
with the appearance of CDA in children at increased risk for the disease.
Celiac disease, also called gluten-sensitive enteropathy, is characterized
by chronic inflammation in the small intestine, resulting in villous atrophy
and flattening of the mucosa, induced by prolamins (gluten) present in wheat,
barley, or rye.1,2 The classic
form of celiac disease typically presents in early childhood with abdominal
pain and diarrhea, malabsorption, and nutrient deficiencies. Most patients
with celiac disease carry the human leukocyte antigen HLA-DRB1*03 allele (usually
associated with HLA-DQ2) or HLA-DRB1*04 (associated with HLA-DQ8).1,3 These alleles also confer increased
risk for type 1 diabetes; thus, individuals with type 1 diabetes and their
first-degree relatives have increased risk of celiac disease.4 However,
few genetically susceptible individuals develop celiac disease, even though
virtually all individuals in wheat-consuming populations are exposed to gluten.
This suggests that additional factors play a role in disease risk.
Previous case-control studies have reported that children with celiac
disease were less likely to have been breastfed or were breastfed for a shorter
period of time than children without celiac disease.5-8 Ivarsson
et al9 found that children with celiac disease
were less likely to have been breastfeeding when gluten was introduced into
the diet than children without celiac disease. While no effect of the timing
of the introduction of gluten into the infant diet on risk of celiac disease
has been observed,5-10 the
greater amount of gluten consumed when first introduced increased risk in
one9 but not in another10 study.
These studies suggest that the infant diet may be important in the etiology
of celiac disease, but they lack consistency, possibly due to limitations
of the case-control study design. Given the known dietary etiology of celiac
disease (ie, gluten intake), it is problematic to examine infant diets after
celiac disease appears because the participant (or the parents) may be sensitized
to the fact that something in the diet “caused” celiac disease
and may respond to dietary surveys in a different way than controls, creating
bias. A better way to examine this question is to collect the exposure data
before the study participants develop disease; however, the low prevalence
of celiac disease precludes a longitudinal study in the general population.
However, HLA genotype can be used to define a higher-risk cohort, and markers,
such as autoantibodies, provide a tool to screen for early presymptomatic
disease. The enzyme tissue transglutaminase (tTG) has been identified as the
celiac disease autoantigen.11 The presence
of tTG autoantibodies is highly sensitive (0.92-1.00) and specific (0.91-1.00)
for celiac disease.12-16
The Diabetes Autoimmunity Study in the Young (DAISY) is a prospective
study of the natural history and environmental triggers of diabetes and celiac
disease autoimmunity (CDA) in genetically predisposed children. Recently we
found that first exposure to cereals in the first 3 months of life or in the
seventh month or later increased risk of type 1 diabetes autoimmunity in children
at risk for diabetes.17 The objective of our
study was to investigate whether there was a similar association between timing
of exposure to cereals and subsequent development of celiac disease–associated
tTG autoantibodies in children with a genetic predisposition for celiac disease.
As in the previous study,17 we used 4 to 6
months of age as the reference period because the American Academy of Pediatrics
recommends the first introduction of solid foods during this time.
DAISY is investigating the natural history of islet and transglutaminase
autoimmunity in infants and children who are at increased risk of developing
type 1 diabetes18 and celiac disease.19 Increased risk is defined either by having a sibling
or parent with type 1 diabetes or having HLA genotypes associated with celiac
disease and type 1 diabetes. Newborn children with a sibling or parent with
type 1 diabetes were identified from families attending clinics in the Denver
metropolitan area, the majority from the Barbara Davis Center for Childhood
Diabetes, and recruited regardless of their HLA genotype. Children were also
identified at St Joseph’s Hospital in Denver, Colo, by screening umbilical
cord blood samples for diabetes- and celiac disease-susceptibility alleles
in the HLA region. The St Joseph’s Hospital newborn population is representative
of the general population of the Denver metropolitan area. We excluded families
in which parents had difficulties understanding English or whose newborn infant
had a severe congenital malformation or disease. Eighty-six percent of the
families approached gave informed consent to the genetic screening.
From December 1993 to January 2003, more than 28 100 cord blood
samples were screened at Roche Molecular Systems Inc, Alameda, Calif. The
details of the newborn screening have been published elsewhere.18 Children
with the following HLA genotypes were invited soon after birth to participate
in the DAISY follow-up: DRB1*03, DQB1*0201/DRB1*03, DQB1*0201; DRB1*04,DQB1*0302/DRB1*03,
DQB1*0201; DRB1*04, DQB1*0302/DRB1*04,DQB1*0302; and DRB1*04,DQB1*0302/x (where
x is neither DRB1*04, DQB1*0302 nor DRB1*03 nor DR2). Two years after their
newborn screening, children with the genotype DRB1*03,DQB1*0201/x were also
invited to participate in follow-up. This was done to supplement the DAISY
cohort with additional children at increased risk for celiac disease. For
the remainder of this report, we refer to DRB1*03,DQB1*0201 as DR3. This study
was approved by the Colorado Multiple Institutional Review Board. Written
informed consent was obtained from the parents of all children.
Infant diet data were collected during telephone or face-to-face interviews
at 3, 6, 9, 12, and 15 months of age in those children enrolled soon after
birth. At each interview, mothers were asked to report all types of milk,
formulas, and foods that the infant consumed over the previous 3 months. If
a particular item was introduced for the first time during that 3-month interval,
the mother was asked to report the date at first introduction. Breastfeeding
initiation and termination were also recorded. For the children enrolled between
the ages of 2 and 3 years, the same dietary information was collected retrospectively
by questionnaire at enrollment, and in all cases before the appearance of
tTG autoantibodies. No dietary advice was given to the families.
Measurement of tTG Autoantibodies
Children followed up from birth had their blood drawn at clinic visits
at 9, 15, and 24 months and annually thereafter for the measurement of tTG
autoantibodies. Children initially enrolled between the ages of 2 and 3 years
had their blood drawn at enrollment and annually thereafter. A radioimmunoassay
with in vitro transcribed and translated human tTG complementary DNA was used
to detect IgA antibodies to tTG in serum samples stored at −20°C,
as previously described.20,21 Briefly,
results were expressed as an index, with the cutoff value corresponding to
3 times the highest value for 184 endomysial antibody-negative healthy control
participants with a median age of 15.6 years.20 Samples
were tested in duplicate, and all positive samples and 10% of negative samples
were confirmed by blinded duplicate testing. In all children, serum total
IgA was measured using a nephelometric method, using a cutoff of 3 SDs below
the age-adjusted norm or 10 mg/dL. In samples from children found to be IgA
deficient, IgG tTG was measured (n = 163), and 2 were positive for
both IgG tTG and IgA tTG. This definition of tTG positivity has previously
been shown to correspond to a 70% to 83% positive predictive value for generally
asymptomatic celiac disease without long-term follow-up in this study cohort.21 Children with a positive tTG result were followed
up more frequently, at 3- to 6-month intervals, with repeated testing. All
of the positive children had at least 1 negative tTG test prior to their positive
tTG test, which means we can determine the interval within which tTG appeared.
Clinical Evaluation and Intestinal Biopsy
After 1 or 2 positive tTG autoantibody results, clinical evaluation
and small bowel biopsy were offered. Clinical evaluation included a physical
examination and a symptom questionnaire. Intestinal biopsy specimens were
obtained initially with a Carey capsule (Wilson-Cook Medical Inc, Winston-Salem,
NC [n = 4]) and then by upper gastrointestinal endoscopy with 2
to 4 specimens from the descending duodenum. A single pathologist (J.E.H.),
blinded to clinical information, assessed the biopsy specimens according to
the scoring system described by Marsh22 (ie,
a score of 0 [normal], 1 [infiltrative lesion with increased intraepithelial
lymphocytes], 2 [hyperplastic lesion with hyperplastic crypts and increased
intraepithelial cells], and 3 [destructive lesion with villous atrophy that
may be subtotal, partial or total]). A score of 2 or 3 is considered confirmatory
for celiac disease.
Definition of CDA Outcome
The outcome of interest was the time to development of CDA, which was
defined as the presence of tTG autoantibodies on 2 consecutive visits or a
positive small bowel biopsy after only a single tTG-positive visit. As a secondary,
more stringent outcome, we limited our CDA cases to only those children who
had a biopsy positive for celiac disease, as defined by a Marsh score of 2
Gluten exposure was defined as intake of foods containing wheat, barley,
or rye, including infant cereals, zwieback, breads, crackers, tortillas, teething
biscuits, cookies, cakes, pretzels, and pasta. We examined oats separately
because, while oats are not a gluten-containing grain, they are often contaminated
by gluten-containing grains during harvesting and milling. We defined rice
exposure as intake of foods containing rice, such as infant rice cereal, boiled
rice, rice milk, rice cakes, or rice noodles. We defined exposure to cow’s
milk as intake of any formulas, milk, or foods containing cow’s milk,
yogurt, cheese, or milk products of any kind. We examined 2 variables related
to breastfeeding: (1) duration of breastfeeding (including partial), and (2)
whether or not the child was still breastfed when first exposed to gluten.
We examined descriptive variables such as sex, maternal education level (categorized
as ≤12 or >12 years), and maternal age (in years). We examined race/ethnicity
as a potential confounder because of (1) differences in risk of celiac disease
by race/ethnicity23 and (2) differences in
infant diet choices by race/ethnicity.24 Parents
reported the race/ethnicity of their child. HLA-DR3 status (HLA-DR3/3, DR3/X
vs all other) and family history of type 1 diabetes were examined as potential
covariates because they comprised the inclusion criteria for the cohort.
All analyses were performed with SAS version 8 (SAS Institute Inc, Cary,
NC). Pearson correlation coefficients were used to examine the correlation
between the ages at introduction of cereals and milks into the infant diet.
Ongoing recruitment since 1994 and continuing follow-up have resulted in variable
lengths of follow-up for the children, producing right-censored data. We began
the calculation of follow-up time at birth, and the age of the first positive
tTG autoantibody measurement was used to define the time to event. Kaplan-Meier
curves were used to describe the risk of CDA by age and in the different exposure
groups, and differences in these curves were tested using the Wilcoxon test
for equality over strata. Our data are interval-censored because we only know
the time of the last negative and first autoantibody-positive blood draw,
rather than the actual time of conversion to autoantibody positivity. Therefore,
all unadjusted and adjusted hazard ratios (HRs) were estimated using survival
analysis (SAS Proc Lifereg) accounting for right and interval censoring.25 The Weibull distribution was chosen after a comparison
of survival models using different distributions found the Weibull distribution
to be the better fit. Variables were included in the final model if they were
statistically significant (based on the Wald χ2P value) or if their inclusion in the model altered the HR of the variable
of interest by 10% or more. A P value of <.05
was considered statistically significant.
Of the HLA-screened newborns, 55% of families agreed to participate.
Of the HLA-screened children recruited at age 2 to 3 years, 67% agreed to
participate. We do not have a denominator to calculate the participation rate
of those recruited from clinics. We obtained outcome data (tTG autoantibodies)
on 84% of children for whom we collected infant diet information. Therefore,
the analysis cohort comprised 1560 children, including 1307 children who were
followed up from birth (311 [20%] with a family history of type 1 diabetes
who were identified at clinics and 996 [64%] identified by newborn HLA screening)
and 253 (16%) children followed up from the age of 2 to 3 years. Fifty-one
children had CDA, 50 with 2 positive tTG autoantibody measurements and 1 with
a single positive measurement and a positive small bowel biopsy. Of these
51 children, 32 completed the study evaluation and biopsy, 2 had a biopsy
outside the study, and 17 did not have a biopsy.
The majority of the children (73% [n = 1140]) were non-Hispanic
white. The remaining 420 children were Hispanic (n = 320; 21% of
total), biracial (n = 50; 3%), African American (n = 36;
2%), or other race or missing (n = 14; 1%). More than 1 sibling
from a family was included in some instances—2 siblings from 143 families
and 3 siblings from 10 families. Eighty-seven percent (n = 1356)
of the cohort was breastfed. Breastfeeding duration was correlated with age
at first exposure to rice cereals (r = 0.25
[P<.001]) and with oat cereals (r = 0.18 [P<.001]), but not with
cereals containing wheat, barley, or rye (r = 0.03
[P = .31]). Ages at first exposure to rice
and oat cereals were correlated with age at first exposure to cereals containing
wheat, barley, or rye (r = 0.27 [P<.001] and r = 0.34
Figure 1 displays the percentage
of children exposed to breast milk, cow’s milk, rice, oats, and wheat,
barley, or rye at different ages in months. By their 6-month birthday, 87%
of the children were eating rice, 40% were eating oats, and 40% were eating
wheat, barley, or rye, largely in the form of cereals. At this same age, 48%
of the children were still breastfed and 75% had been exposed to cow’s
milk, largely in the form of infant formula.
Table 1 describes the clinical
and symptomatic characteristics of the tTG autoantibody–positive children
by biopsy status. Children who did not have a biopsy were slightly older than
those who did have a biopsy, but were similar to children undergoing biopsy
in terms of HLA-DR3 status, highest tTG autoantibody level, and presence of
symptoms. Children with a negative biopsy were similar to those with a positive
biopsy in terms of HLA-DR3 status, but were slightly younger, had lower tTG
autoantibody levels, and were less likely to report symptoms, likely reflecting
an earlier course of the disease.
Infant Diet Exposures and Risk of CDA
The mean (SD) age at first positive tTG autoantibody test for the 51
CDA-positive children was 4.7 (1.5) years, and the mean (SD) age at the last
follow-up for the 1509 CDA-negative children in the cohort was 4.8 (2.9) years
(Table 2). Of the CDA-positive children,
3 (6%) were exposed to wheat, barley, or rye at 1 to 3 months, 12 (23%) at
4 to 6 months, and 36 (71%) at 7 months or later, vs 40 (3%), 574 (38%), and
895 (59%) of CDA-negative children. Kaplan-Meier curves displaying the proportion
of children becoming CDA positive by time period of exposure to wheat, barley,
or rye were significantly different from each other (P = .04)
(Figure 2). All of the variables listed
in Table 2 were considered for inclusion
in the multivariate survival analysis model, and only HLA-DR3 status met the
statistical criteria for inclusion. Adjusting for HLA-DR3 status, children
exposed to wheat, barley, or rye in the first 3 months of life had a 5-fold
increased hazard of CDA compared with those who were exposed at 4 to 6 months
(Table 3). Children not exposed to wheat,
barley, or rye until their seventh month or later were at a slightly increased
hazard of CDA compared with those who were exposed in the 4- to 6-month period,
which was only marginally significant. Further adjustment for the other cereal
variables demonstrated that the association between CDA and exposure to wheat,
barley, or rye was independent of the age at first exposure to rice and to
oats. Of the 25 children with biopsy-confirmed CDA-positive status, 3 (12%)
were exposed to wheat, barley, or rye at 1 to 3 months, 3 (12%) at 4 to 6
months, and 19 (76%) at 7 months or later vs 40 (3%), 583 (38%), and 912 (59%)
of unaffected children, respectively. Initial exposure to wheat, barley, or
rye in the first 3 months or in the seventh month or later significantly increased
risk of biopsy-confirmed CDA compared with exposure at 4 to 6 months (Table
To examine whether the inclusion of the 253 children with retrospective
dietary data may have affected our findings, we limited our cohort to only
those children for whom data were collected prospectively (n = 1307
children, of whom 43 were CDA positive). The adjusted HRs for exposure to
wheat, barley, or rye at 0 to 3 months and 7 months or later (compared with
4-6 months) were 7.49 (95% confidence interval [CI], 1.53-36.60) and 2.96
(95% CI, 1.31-6.67) respectively, suggesting an increased risk of CDA for
both early and late initial exposure to wheat, barley, and rye. This subanalysis
suggests that inclusion of children with retrospective data did not negatively
affect our results.
To determine whether inclusion of multiple siblings per family affected
our results, we randomly selected 1 sibling per family and reran our analyses.
The adjusted HRs for exposure to gluten at 0 to 3 months and 7 months or later
(compared with 4-6 months) were 5.65 (95% CI, 1.19-26.78) and 2.39 (95% CI,
1.09-5.25) respectively, suggesting an increased risk of CDA for both early
and late initial exposure to wheat, barley, and rye. This subanalysis suggests
that inclusion of multiple siblings did not affect our results.
We then limited our analyses to the children at highest risk for celiac
disease, those who have at least 1 HLA-DR3 allele (n = 777), in
whom 43 cases of CDA developed. Kaplan-Meier curves showing the proportion
of children becoming CDA positive by month of exposure to wheat, barley, or
rye in HLA-DR3–positive children were significantly different from each
other (P = .004) (Figure 2). Of the 14 DR3-positive children who were exposed to wheat,
barley, or rye in the first 3 months of life, the risk of CDA was 40% by 5.5
years of age. The HRs (95% CIs) for CDA in children initially exposed to wheat,
barley, or rye in the first 3 months or not until the seventh month or later
were 7.28 (2.02-26.25) and 1.68 (0.84-3.36), respectively, compared with children
exposed in the 4- to 6-month period, suggesting an increased risk of CDA with
early exposure to wheat, barley, and rye in HLA-DR3–positive children.
It was not possible to test for an interaction between HLA-DR3 and timing
of exposure to gluten because there were no CDA cases that were DR3 negative
and exposed in the first 3 months of life.
We found an association between timing of initial exposure to wheat,
barley, and rye and the development of CDA. Wheat, barley, and rye are closely
related grasses that contain prolamins, or storage proteins, that induce the
autoimmune process in patients with celiac disease.26 Treatment
for celiac disease is a gluten-free diet, which essentially eliminates foods
containing wheat, barley, and rye from the diet, as well as gluten used as
an additive. While we combined wheat, barley, and rye into a single exposure
category, it should be noted that wheat and barley made up the great majority
of exposures in infants because of the availability of commercial cereals
made from wheat and/or barley. Individuals with celiac disease are also advised
to avoid oats because they may be contaminated with wheat (and thus gliadin)
through the harvesting and milling process, even though oats themselves are
well-tolerated by most individuals with celiac disease.27-31 We
found no association between the development of CDA and the timing of introduction
of oats or of rice, suggesting that the association is antigen-specific.
We chose our reference group to be those exposed at 4 to 6 months because
pediatricians in the United States generally recommend the introduction of
solid foods, particularly cereals, between 4 and 6 months, although there
is no official American Academy of Pediatrics practice guideline regarding
this.32 Our data suggest that introducing foods
containing gluten in the first 3 months of life increases a child’s
risk of CDA. Interestingly, waiting until the seventh month or later to first
introduce foods containing gluten marginally increases the risk for CDA compared
with introducing gluten in the 4- to 6-month period.
We were not able to confirm celiac disease in all tTG autoantibody–positive
children via small bowel biopsy. To examine whether our findings might be
generalizable to celiac disease itself, we restricted our CDA cases to those
25 children who were subsequently diagnosed with celiac disease based on small
bowel biopsy and found that initial exposure to wheat, barley, or rye in the
first 3 months or in the seventh month or later significantly increased risk.
This suggests a window of exposure to gluten outside of which one may increase
CDA risk in susceptible children.
Gliadin deamidation by tTG has been demonstrated to enhance the recognition
of gliadin peptides by T cells and this might initiate the cascade of autoimmune
reactions leading to celiac disease.33,34 For
this to happen, gliadin has to cross the intestinal epithelial barrier so
that it can be recognized by antigen-presenting cells. While the intestinal
barrier functions as the major organ of defense against foreign antigens,
toxins, and macromolecules entering the host via the oral route, at very young
ages this barrier may not be as complete as at older ages, thus allowing gliadin
to pass even with small amounts of intake.
The reason why late gluten exposure is also associated with CDA is less
clear. When wheat is introduced to an older child, it tends to be introduced
in greater amounts, thus increasing the amount of gliadin available to cross
the gut. Even if a small proportion of the available gliadin crosses the gut,
it may be sufficient to initiate the cascade. Ivarsson et al9 found
that children with celiac disease were exposed to a larger amount of gluten
at first exposure than children without celiac disease, and that this amount
at initial exposure increased the later in life gluten was introduced. In
our study, infants first exposed to cereals at or after the seventh month
were more likely to have been given 1 or more servings per day in the first
month of exposure compared with children who were first exposed before 4 months
(52% vs 31%, respectively), suggesting that the frequency of exposure at initial
introduction increased with age. The recent finding that gliadin may actually
activate a zonulin-dependent enterocyte intracellular signaling pathway leading
to increased intestinal permeability33 suggests
a cycle where dietary intake of gliadin would lead to increasing intestinal
permeability via the activation of zonulin by gliadin, which would in turn
lead to greater and greater exposures to the body with continued gliadin intake.
Although all children in our cohort were exposed to gluten by 12 months
of age, the first positive tTG autoantibody result did not occur until 2 years
of age, with a mean age at conversion of 4.7 years, showing a delay in the
appearance of tTG autoantibodies. This might be due to less sensitive serology
in the youngest age group. We were not aware of data on human tTG autoantibodies
in children younger than 2 years, so we reviewed laboratory data on diabetic
individuals at the Barbara Davis Center for Childhood Diabetes. Tissue transglutaminase
autoantibodies were present at diabetes onset in 5.7% of children younger
than 2 years and in 7.8% of older children, suggesting that tTG autoantibodies
are detectable at young ages with our assay (G.S.E., unpublished data, 2005).
Therefore, the delayed appearance of tTG autoantibodies is consistent with
an immature developing immune system slowly responding to exposure to gluten
and fueled by continued gluten exposure and perhaps other exposures as well.
This recognition of a delay in appearance of autoantibodies is reflected in
a recent recommendation to screen high-risk asymptomatic children for tTG
autoantibodies after the age of 3 years, provided they have been receiving
an adequate gluten-containing diet for at least 1 year.35
Because of the similarities between the epidemiology of celiac disease
and type 1 diabetes and the coexistence of the 2 diseases in the same individuals
or families, gluten exposure is also a candidate risk factor for type 1 diabetes.36 We recently published findings from the DAISY cohort
showing that children initially exposed to cereals in the first 3 months of
life and those who were not exposed until the seventh month or later had an
increased risk of islet autoimmunity compared with those who were exposed
at 4 to 6 months.17 However, the association
with islet autoimmunity was not specific to gluten-containing foods. Due to
differences in inclusion and exclusion criteria, the cohort from our previous
report and that of the current study are not entirely the same, although they
are drawn from the same DAISY population. Only 3 children were positive for
both islet autoimmunity and CDA, and thus were counted as cases in both analyses,
so it is unlikely that one form of autoimmunity is driving the association
of the other. Ziegler et al37 found that exposure
to gluten in the first 3 months of life increased risk of islet autoimmunity
5-fold in offspring of type 1 diabetic individuals. The investigators also
reported an inverse relationship between age at gluten exposure and tTG autoantibody
risk, but this was not significant, perhaps due to the small number of tTG
autoantibody cases. These prospective studies of 2 childhood autoimmune diseases
suggest that this period during infancy is important for the development of
the immune system and potentially in determining the difference between tolerance
and sensitization to specific food antigens.
We did not observe the protective effect of breastfeeding reported in
previous retrospective case-control studies.5-9 Aside
from the methodological differences between retrospective and prospective
studies regarding selection and recall bias, this lack of replication may
be related to inherent infant diet differences across studies. The studies
showing a protective association of breastfeeding were done in Europe where
infant diet practices may be different compared with the United States. In
our population, the first exposure to wheat, barley, or rye was primarily
in the form of infant cereals, which are not replacements for breast milk
and in fact are not correlated with breastfeeding duration. In other countries,
the primary exposure to gluten may be more correlated with breastfeeding duration,
for example, the flour-based follow-up infant formula used in Sweden. The
previous studies may not have been able to disentangle breastfeeding from
gluten introduction due to imprecision in their retrospective data.
In summary, timing of gluten introduction into the infant diet is associated
with risk of CDA. We note that our outcome was not celiac disease per se;
however, our analysis of CDA cases with biopsy-confirmed celiac disease suggests
that this association may exist with clinical disease as well. Given that
our study population was selected for specific genetic and family history
characteristics, our findings are generalizable only to children at increased
risk for celiac disease. We cannot exclude the possibility that earlier exposure
to gluten simply leads to earlier appearance of CDA and that all exposed at-risk
children will eventually develop CDA. Long-term follow-up of this cohort may
be necessary to address this question. Given the small number of CDA-positive
children and wide CIs, we recommend that these results be confirmed in other
prospective cohorts of children at risk for celiac disease before any interventions
are implemented. Additional studies may shed light on the importance of quantity
of exposure and whether the risk is related to exposure to antigens or to
other components of cereals. Our results support continuing current US feeding
recommendations for introduction of cereal in infants at 4 to 6 months.
The American Academy of Pediatrics recently published a policy statement
recommending exclusive breastfeeding for the first 6 months of life, with
the gradual introduction of complementary foods (eg, cereals, etc) beginning
around 6 months of age. The Academy acknowledges that “unique needs
or feeding behaviors of individual infants [could] indicate a need for introduction
of complementary foods as early as 4 months of age. . . . ”38
Corresponding Author: Jill M. Norris, MPH,
PhD, Department of Preventive Medicine and Biometrics, University of Colorado
at Denver and Health Sciences Center, 4200 East Ninth Ave, Box B119, Denver,
CO 80262 (firstname.lastname@example.org).
Author Contributions: Drs Norris and Rewers (principal investigator) had full access to all of the
data in the study and take responsibility for the integrity of the data and
the accuracy of the data analysis.
Study concept and design: Norris, Hoffenberg,
Acquisition of data: Norris, Hoffenberg, Taki,
Miao, Haas, Emery, Erlich, Eisenbarth, Rewers.
Analysis and interpretation of data: Norris,
Barriga, Hoffenberg, Sokol, Erlich, Eisenbarth, Rewers.
Drafting of the manuscript: Norris, Hoffenberg.
Critical revision of the manuscript for important
intellectual content: Norris, Barriga, Taki, Miao, Haas, Emery, Sokol,
Erlich, Eisenbarth, Rewers.
Statistical analysis: Norris, Barriga.
Obtained funding: Norris, Eisenbarth, Rewers.
Administrative, technical, or material support:
Norris, Emery, Erlich, Rewers.
Study supervision: Norris, Taki, Rewers.
Protocol development: Norris, Erlich, Eisenbarth,
Clinical component development: Hoffenberg.
HLA genotyping: Erlich.
Measurement of autoantibodies: Miao, Eisenbarth.
Clinical evaluation of antibody-positive children: Hoffenberg, Haas, Sokol.
Database preparation and management: Barriga,
Study coordinator: Taki.
Financial Disclosures: None reported.
Funding/Support: This research was supported
by National Institutes of Health grants R01-DK32493, DK50979, DK32083, DK49654,
Autoimmune Prevention Center AI 50864, Diabetes Endocrine Research Center,
Clinical Investigation & Bioinformatics Core P30 DK 57516, and the General
Clinical Research Centers Program, National Center for Research Resources
Role of the Sponsors: The funding sources did
not participate in the design and conduct of the study; in the collection,
analysis, and interpretation of the data; or in the preparation, review, or
approval of the manuscript.
Acknowledgment: We would like to acknowledge
the dedicated and talented staff of the DAISY study for their clinical, data,
and laboratory support. We are indebted to all of the children and their families
who generously volunteered their time and knowledge.
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