Antibiotic Use Associated with Higher Celiac Disease Risk

http://www.biomedcentral.com/content/pdf/1471-230X-13-109.pdf



Antibiotic exposure and the development of
coeliac disease: a nationwide case–control study
Karl Mårild1,2*, Weimin Ye3
, Benjamin Lebwohl4
, Peter HR Green4
, Martin J Blaser5
, Tim Card6
and Jonas F Ludvigsson1,7



Abstract

Background: The intestinal microbiota has been proposed to play a pathogenic role in coeliac disease (CD).
Although Antibiotics are common environmental factors with a profound impact on intestinal microbiota, data on
Antibiotic use as a risk factor for subsequent CD development are scarce.
Methods: In this population-based case–control study we linked nationwide histopathology data on 2,933
individuals with CD (Marsh stage 3; villous atrophy) to the Swedish Prescribed Drug Register to examine the
association between use of systemic Antibiotics and subsequent CD. We also examined the association between
Antibiotic use in 2,118 individuals with inflammation (Marsh 1–2) and in 620 individuals with normal mucosa (Marsh
0) but positive CD serology. All individuals undergoing biopsy were matched for age and sex with 28,262 controls
from the population.

Results: Antibiotic use was associated with CD (Odds ratio [OR] = 1.40; 95% confidence interval [CI] = 1.27-1.53),
inflammation (OR = 1.90; 95% CI = 1.72–2.10) and normal mucosa with positive CD serology (OR = 1.58; 95%
CI = 1.30–1.92). ORs for prior antibiotic use in CD were similar when we excluded antibiotic use in the last year
(OR = 1.30; 95% CI = 1.08-1.56) or restricted to individuals without comorbidity (OR = 1.30; 95% CI = 1.16 – 1.46).
Conclusions: The positive association between antibiotic use and subsequent CD but also with lesions that may
represent early CD suggests that intestinal dysbiosis may play a role in the pathogenesis of CD. However,
non-causal explanations for this positive association cannot be excluded.
Keywords: Celiac, Inflammation, Microbiota, Population-based case–control study


Background

Coeliac disease (CD) is a life-long autoimmune disease
prevalent in 1 to 2% of the western population [1]. CD is
a multifactorial disease where genetically predisposed
individuals develop small-intestinal villous atrophy and
inflammation in response to dietary gluten intake [2].
In recent decades, the prevalence of CD has more than
doubled, [3] strongly indicating that environmental
factors other than gluten-exposure may have a significant
influence on CD development [4]. Further, data
from the “Swedish celiac epidemic”, where childhood
CD incidence displayed an epidemic pattern with a
rapid four-fold increase in incidence in 1984 and a
later abrupt decline in 1996, coinciding with changed
infant feeding recommendations, have suggested that
environmental factors influence CD development [5].
Today, half of all children in many Western countries
receive Antibiotics at least once a year [6]. Antibiotics
can have both short- and long-term effects on the ecological
balance between the host and the normal
microbiota [7,8]. The intestinal microbiota influences
the development of the intestinal immune system, the
establishment of oral tolerance and the mucosal barrier
function [9]. Previous research has found a difference
in the gut microbiota between individuals with CD and
healthy controls, suggesting that a dysbiotic microbiota
may play a pathogenic role in CD [10]. Despite the profound
impact of antibiotics on the gut microbiome, there
are few data on antibiotic exposure and risk of CD. * Correspondence: karlmarild@gmail.com 1
Clinical Epidemiology Unit, Karolinska Institutet, Stockholm, Sweden
2
Astrid Lindgren Children’s Hospital, Solna, Sweden
Full list of author information is available at the end of the article
© 2013 Mårild et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
Mårild et al. BMC Gastroenterology 2013, 13:109
http://www.biomedcentral.com/1471-230X/13/109The main objective of this case–control study was to
examine the association between antibiotic use and subsequent
CD by comparing individuals with CD with matched
controls from the general population. We also examined
antibiotic use in individuals who may have early CD
without villous atrophy [11] (I) small-intestinal inflammation
without villous atrophy, or (II) normal small-intestinal
mucosa but positive CD serology. Studying these early
CD manifestations may be important because risk factors
may not only influence the fully developed disease, but
sometimes have an even stronger association with disease
precursors. For example, cigarette smoking has been more
strongly associated with colorectal adenomas compared
with colorectal cancer [12,13].


Methods

In this case–control study we linked nationwide histopathology
data on individuals undergoing small intestinal
biopsy to the Swedish Prescribed Drug Register in
order to examine the association between use of antibiotics
and CD. We hypothesized a positive association between
antibiotic use and CD.
Literature search
A literature search at PubMed (http://pubmed.gov/) was
performed using the following combinations of words as
our major search terms: “celiac”, “coeliac”, “antibiotic” and
“antimicrobial”.
Study population
Between 2006 and 2008, we searched the computerized
register of Sweden’s 28 pathology departments to identify
individuals with CD [14]. In this study CD was defined
as small-intestinal villous atrophy (Marsh grade 3) [15].
An earlier evaluation has shown that 95% of Swedish individuals
with villous atrophy have CD [14]. To examine
the context of the association between antibiotic use and
subsequent CD we also identified individuals with smallintestinal
inflammation (Marsh grade 1–2) but without
villous atrophy and individuals with normal small-intestinal
mucosa (Marsh grade 0) but with positive CD serology
[16]. The biopsies were performed between July 1969 and
January 2008 [17]. A detailed account of the data collection
process has been described elsewhere [14,16].
In the current study we used the same dataset described
in our previous study of mortality (29,096 individuals with
CD, 13,306 individuals with inflammation, 3,719 individuals
with normal mucosa but positive CD serology) [18].
Data on individuals with normal mucosa and positive
CD serology were regional and obtained from the ascertainment
areas of eight Swedish university hospitals
covering approximately half of the Swedish population
[16]. Positive CD serology was defined as a positive IgA
or IgG AGA (antigliadin), EMA (endomysial), or TTG
(tissue transglutaminase) test less than 180 days before
or no later than 30 days after a normal biopsy (and with
no prior or subsequent biopsy showing villous atrophy or
inflammation) [16]. In a recent consensus paper individuals
with normal mucosa and positive CD serology were
identified as having potential CD [11].
For each individual undergoing biopsy, the government
agency Statistics Sweden identified up to five controls
from the population matched for age, sex, calendar period
of birth and county of residence. For example, a girl living
in the county of Blekinge, diagnosed with CD in 2006 at
the age of 13 years; was matched with five 13-year-old
girls who were living in Blekinge in 2006. After exclusion
of individuals with data irregularities, [18] we identified
228,632 controls (Figure 1).
Individuals undergoing biopsy and their matched controls
were then linked to the Swedish Prescribed Drug Register
(established on July 1st 2005) [19]. Through this linkage,
we identified individuals biopsied between July 1st 2005
and January 29th 2008 (end of the study period). Thus,
the final analyses included 2,933 individuals with CD,
2,118 individuals with inflammation, 620 individuals
with normal mucosa but positive CD serology and 28,262
controls (Figure 1).
Antibiotic use
The Swedish Prescribed Drug Register contains prospectively
recorded individual data (on e.g. date of dispensing)
on more than 99% of all dispensed prescribed drugs in
Sweden [19]. Antibiotics in Sweden are not sold over
the counter.
We collected data on use of all systemic antibiotics
(anatomical therapeutic chemical, ATC code: J01) from
July 1st 2005 (launch of the Prescribed Drug Register)
through January 29th 2008 (end of the study period), and
up to the date of the biopsy (and the corresponding date in
matched controls). Antibiotics were grouped into penicillin
V, extended-spectrum penicillins, quinolones, macrolides
and other systemic antibiotics (Additional file 1).
Statistical analyses
We used conditional logistic regression to estimate odds
ratios (ORs) and 95% confidence intervals (CIs). Each
stratum (one individual undergoing biopsy and up to
five matched controls) was analyzed separately before a
summary OR was calculated.
In our main analysis we examined the association
between use of any systemic antibiotics and subsequent
CD. Early-onset CD (i.e. before the age of 2 years) may
have different risk factors compared with late-onset CD
[5]. Additionally, antibiotic exposure early in life may have
a more profound impact on the composition of the microbiota
[20]. Accordingly, we performed stratified analyses
by age at CD diagnosis (<2 years, 2–19 years, 20–39 years,
Mårild et al. BMC Gastroenterology 2013, 13:109 Page 2 of 9
http://www.biomedcentral.com/1471-230X/13/10940–59 years and ≥60 years). We also stratified our analyses
for sex. Similar sub-analyses were performed for individuals
with small-intestinal inflammation and individuals with
normal small-intestinal mucosa but positive CD serology.
For each of these stratifications we examined for interaction
via the inclusion in our models of multiplicative interaction
terms, and the use of likelihood ratio tests between models
with and without them.
Antibiotics differ in their influence on the intestinal
microbiota. In pre-planned sub-analyses we estimated the
association between CD and type of antibiotic exposure:
penicillin V, extended-spectrum penicillins, quinolones,
macrolides and other systemic antibiotics. This grouping
of antibiotics has previously been used [21,22] and is
largely based on the ATC classification system where the
subgroups indicate the different therapeutic indications of
antibacterial agents. To evaluate potential causality we
estimated the dose- and time-dependent association
between antibiotic use and CD in two separate analyses:
(1) when individuals had received 1–2 courses and at least
3 courses of antibiotics and (2) when antibiotics had been
prescribed in the year (≤365 days) before biopsy.
Education level has been associated with antibiotic use
[23] and may influence the risk of CD diagnosis [24]. In
a sub-analysis we therefore adjusted for education using
seven predefined education categories determined by
Statistics Sweden.
Post-hoc analyses
Certain antiparasitic medications have similar pharmacokinetic
and pharmacodynamic properties as systemic
antibiotics with a strong impact on the gut microbiota.
In a post-hoc analysis we therefore examined the relationship
between use of any antiparasitic medications
(ATC codes P01-P03, e.g. oral tinidazole) and CD, as
well as specifically the use of metronidazole and CD.
Individuals with undiagnosed CD have an increased risk
of comorbidity, [25] and with that, potentially increased
surveillance and probability to receive antibiotic treatment.
In a post-hoc analysis we therefore restricted our data to
individuals who had not been admitted to a hospital during
the study period. Hospital admission data were collected
from the national Inpatient Register [26].
To further reduce the risk of surveillance bias we
constructed a variable representing outpatient health care
consumption. Hospital-based outpatient care has been
recorded nationally in Sweden since January 1st 2001. We
calculated the number of hospital-based outpatient visits
from birth or start of the registry (whichever occurred latest)
until the day before small-intestinal biopsy (or corresponding
date in matched controls). We excluded visits in which
CD was coded as the main reason for the visit. Individuals
then were divided into four groups according to number of
visits per year (those with no record of prior hospital-based
outpatient care (0); >0 but <1 visit/year; 1- < 2 visits/year;
and ≥2 visits/year). Those individuals with no record of
hospital-based outpatient care may have undergone initial
CD investigation in primary care before undergoing biopsy.
For example: A patient A, undergoing biopsy in December
2006, with eight hospital-based outpatient visits in the six
years between 2001 (start of registration of outpatient data)
and December 2006 (time of biopsy) has an average of 1.3
visits per year (= 8 visits/6 years). In a post-hoc analysis,
we added this variable to our statistical model to evaluate
whether the association between antibiotic exposure and
CD remained.
CD is elicited by dietary gluten and thus virtually
nonexistent before the age of six months. To establish
Figure 1 Flow chart of exclusion criteria. CD, Coeliac disease.
Mårild et al. BMC Gastroenterology 2013, 13:109 Page 3 of 9
http://www.biomedcentral.com/1471-230X/13/109whether antibiotic use truly preceded CD, i.e. to evaluate
the risk of reverse causation, we performed a sub-analysis
of individuals who were exposed to antibiotics before the
age of six months. In an additional post-hoc analysis we
limited our exposure to antibiotic more than one year
(>365 days) before CD diagnosis.
SPSS version 20.0 was used for all statistical analyses.
Ethics
This study was conducted in accordance with the national
and institutional standards and was approved by the
Regional Ethical Vetting Board in Stockholm.
Results
The median age at CD diagnosis in this study was
28 years. About 40% of those with CD were diagnosed
in childhood and the majority of study participants were
female (Table 1).
Of the 2,933 individuals with CD, 27.0% had received
at least one course of antibiotics during the study period
before biopsy as compared with 21.1% in the controls,
corresponding to an odds ratio for subsequent CD of
1.40 (95% CI = 1.27-1.53) (Table 2). In the individuals
with inflammation but no villous atrophy 39.5% had
used antibiotics as compared with 25.7% in the controls
(OR = 1.90; 95% CI = 1.72–2.10). Antibiotic use also was
associated with having a normal small-intestinal mucosa
but positive CD serology (Table 2). Restricting our analysis
to individuals with normal mucosa and positive IgA EMA
or TTG did not influence the OR (Additional file 2).
Adjustment for education level revealed unchanged ORs
in all three groups (Additional file 2).
We found increasing ORs for repeated use of antibiotics
and subsequent CD diagnosis (1–2 courses of antibiotics:
OR = 1.36, 95% CI = 1.23-1.50; ≥3 courses of antibiotics:
OR = 1.58, 95% CI = 1.31 - 1.92). Also in individuals
with a biopsy showing inflammation or normal mucosa,
but with positive CD serology, we found increasing ORs
for repeated use of antibiotics, indicating a dose–response
effect (Table 2).
The association between antibiotic treatment and
subsequent CD was similar in males and females
(Males: OR = 1.48, 95% CI = 1.27-1.72; Females: OR = 1.36;
95% CI = 1.21-1.52; p-value for interaction: 0.38). The
stratified analyses by sex for individuals with smallintestinal
inflammation and individuals with normal
mucosa but positive CD serology are also presented in
Table 2 (p-value for interaction, inflammation: 0.16; normal
mucosa: 0.15). The stratified analyses by age at biopsy
revealed only small differences between age groups and
ORs for antibiotic treatment and development of CD,
small-intestinal inflammation or normal mucosa but
positive CD serology (Additional file 3). ORs for previous
antibiotic treatment did not differ appreciably according to
year of CD diagnosis (Additional file 3).
Overall, penicillin V was the most frequently prescribed
antimicrobials, being used by 9.0% of the controls and
nearly 10% of those with CD. Use of penicillin V was
not associated with CD (OR = 1.12; 95% = 0.98 – 1.27).
However, we found an association between use of each
of the remaining types of antibiotic and subsequent CD,
with essentially similar ORs, irrespective of antibiotic
type (Table 3).
Twenty-five percent of the individuals with CD had
received at least one course of antibiotics in the year
before CD diagnosis compared with 18.7% of the matched
controls (OR = 1.42; 95% CI = 1.29 - 1.56). ORs for type
of antibiotic, according to ATC code, used in the year
(≤365 days) before CD diagnosis are presented in Table 3.
Post-hoc analyses
In a post-hoc analysis 115 individuals with CD (3.9%) and
259 controls (1.8%) had an earlier record of antiparasitic
medication, equivalent to an OR of 2.12 for subsequent
CD (95% CI = 1.72 - 2.62). Looking specifically at the
earlier use of metronidazole revealed a slightly stronger
association with CD (OR = 2.25; 95% CI = 1.71-2.96)
Table 1 Descriptive characteristics of individuals with
coeliac disease, small-intestinal inflammation, and
normal small-intestinal mucosaa
Coeliac
disease
Inflammation Normal
mucosaa
Total 2933 2118 620
Females (%) 1796 (61.2) 1336 (63.1) 396 (63.9)
Males (%) 1137 (38.8) 782 (36.9) 224 (36.1)
Age at study entry
years (median; range)
28; 0-94 43; 0-98 36; 0-84
Age 0–19 (%) 1218 (41.5) 225 (10.6) 150 (24.2)
Age 20–39 (%) 566 (19.3) 684 (32.3) 202 (32.6)
Age 40–59 (%) 583 (19.9) 661 (31.2) 164 (26.5)
Age 60+ (%) 566 (19.3) 548 (25.9) 104 (16.8)
2005b (%) 819 (27.9) 419 (19.8) 149 (24.0)
2006 (%) 1828 (62.3) 1074 (50.7) 304 (49.0)
2007 C (%) 274 (9.3) 582 (27.5) 167 (26.9)
2008 D (%) 12 (0.4) 43 (2.0) -
a Positive coeliac disease serology (IgA/IgG endomysial, tissue
transglutaminase and antigliadin antibodies) 180 days before biopsy and until
30 days after biopsy in individuals with normal mucosa. Endomysial and tissue
transglutaminase antibodies [IgA]: n = 139; Antigliadin antibodies [IgA/IgG] and
endomysial and tissue transglutaminase antibodies [IgG]: n = 481.
b Beginning of study period: July 1st 2005.
c The majority of the pathology departments delivered data on individuals
with small-intestinal pathology undergoing biopsy up to the beginning of year
2007. The remaining pathology departments reported histopathology data to
the end of 2007 or very early 2008. For this reason, our data included fewer
individuals with CD diagnosed in 2007 compared with 2006.
D End of study period: January 29th 2008.
Reference individuals have not been included in the table because their age,
sex and entry year distributions were identical to those of the individuals
undergoing biopsy (due to matching).
Mårild et al. BMC Gastroenterology 2013, 13:109 Page 4 of 9
http://www.biomedcentral.com/1471-230X/13/109Table 2 Odds ratios for prior antibiotic use in individuals with coeliac disease, small-intestinal inflammation and normal mucosaa
Coeliac disease Inflammation Normal mucosaa
Cases Controls Odds
ratio 95% CI
Cases Controls Odds
ratio 95% CI
Cases Controls Odds
ratio 95% CI (%) (%) (%) (%) (%) (%)
Any antibioticsb 793/2933 (27.0) 3081/14571 (21.1) 1.40 1.27-1.53 836/2118 (39.5) 2687/10442 (25.7) 1.90 1.72–2.10 205/620 (33.1) 757/3069 (24.7) 1.58 1.30–1.92
Courses of antibiotics
1-2 courses 639/2779 (23.0) 2573/14063 (18.3) 1.36 1.23-1.50 619/1901 (32.6) 2146/9901 (21.7) 1.75 1.57-1.95 153/568 (26.9) 621/2933 (21.2) 1.45 1.17-1.80
≥3 courses 154/2294 (6.7) 508/11998 (4.2) 1.58 1.31-1.92 217/1499 (14.5) 541/8296 (6.5) 2.50 2.10-2.97 52/467 (11.1) 136/2448 (5.6) 2.28 1.56-3.33
Sex
Males 278/1137 (24.5) 1026/5645 (18.2) 1.48 1.27-1.72 282/782 (36.1) 824/3848 (21.4) 2.10 1.78-2.48 69/224 (30.8) 217/1099 (19.7) 1.93 1.38–2.69
Females 515/1796 (28.7) 2055/8926 (23.0) 1.36 1.21-1.52 554/1336 (41.5) 1863/6594 (28.3) 1.81 1.60-2.04 136/396 (34.3) 540/1970 (27.4) 1.43 1.12–1.82
Odds ratios estimated through conditional logistic regression modelling.
a Positive coeliac disease serology 180 days before biopsy and until 30 days after biopsy in individuals with normal mucosa.
b Antibiotics used between July 1st 2005 and January 29th 2008.
Mårild et al. BMC Gastroenterology 2013, 13:109 Page 5 of 9
http://www.biomedcentral.com/1471-230X/13/109(metronidazole use in the year before CD diagnosis:
OR = 2.38; 95% CI = 1.78-3.19; and ≥ three courses of
metronidazole: OR = 1.90; 95% CI = 0.62-5.78). Use of
metronidazole was similarly associated with small-intestinal
inflammation and normal mucosa but positive CD serology
(Additional file 4).
To reduce the confounding effect of comorbidity
we restricted our data to individuals with no hospital
admissions (CD: n = 2,047; controls: n = 12,069). However,
this post-hoc analysis revealed only a marginally
changed OR for subsequent CD in relation to antibiotic
use (OR = 1.30; 95% CI = 1.16 – 1.46). Post-hoc adjustment
for number of outpatient visits before biopsy slightly
changed the OR for CD (OR = 1.19; 95% CI = 1.08-1.31).
Further, antibiotic use more than one year before biopsy
examination was also associated with subsequent CD
(OR = 1.30; 95% CI = 1.08-1.56).
We also estimated the OR for subsequent CD based
on use of any antibiotics during the first six months of
life. Only 3 of 16 (18.8%) children born after July 2005
and subsequently diagnosed with CD had been exposed
to any antibiotics during their first six months of life,
as compared with 7/80 (8.8%) children in the controls
(OR = 2.26; 95% CI = 0.55-9.25).
Discussion
This is the first study to find a positive association between
antibiotic use and subsequent CD. Antibiotic exposure
was also linked to small-intestinal inflammation and
to normal mucosa with positive CD serology, both of
which may represent early CD. The consistent association
between the multiple groups, the slightly stronger association
between repeated use of antibiotics compared
with no use as well as the association with use of certain
antibiotics (e.g., metronidazole) and CD may suggest
that antibiotic exposure, possibly through a changed gut
microbiota, plays a pathogenic role in early CD development.
However, given the lack of time-response effect,
within the limited time window studied, we cannot rule
out non-causal explanations for our findings.
Observational studies on drugs are particularly susceptible
to the concerns of reverse causation and confoundingby-indication.
Reverse causation defines the causality bias if
the exposure is a response to manifestations of the undiagnosed
disease. In CD it is difficult to date the true onset of
disease and thereby to establish whether antibiotic use truly
preceded CD or whether the antibiotic was given for the
symptoms of as yet undiagnosed CD. Several studies have
shown a mean diagnostic delay of 5–11 years from onset of
CD symptoms until diagnosis, [27] a time associated with
an increased number of consultation visits [28] and possibly
an increased likelihood of receiving antibiotic prescriptions.
To reduce the risk of reverse causation and the effect of
comorbidity, which may act as a confounder by increasing
the possibility of receiving antibiotic prescriptions, we
performed two post-hoc analyses restricted to individuals
exposed to antibiotics in the first six months of life or individuals
without hospital admission. Although these post-hoc
analyses revealed largely unchanged ORs, they do not rule
out residual comorbidity or reverse causation.
Observational studies on drugs may also be subject to
confounding-by-indication in which the indication for
Table 3 Odds ratios for prior antibiotic a use in individuals with coeliac disease
Coeliac disease
Cases Controls Odds ratio 95% CI
n = 2,933 (%) n = 14,571 (%)
Type of antibiotics used b
Penicillin V 291 (9.9) 1308 (9.0) 1.12 0.98 – 1.27
Extended spectrum penicillins 183 (6.2) 657 (4.5) 1.38 1.18 – 1.63
Quinolones 51 (1.7) 170 (1.2) 1.46 1.08 – 1.97
Macrolides 53 (1.8) 180 (1.2) 1.44 1.07 – 1.93
Other systemic antibiotics 291 (9.9) 1041 (7.1) 1.42 1.24 – 1.62
Antibiotic use in the last year preceding diagnosis/study entry
Any antibiotic 722 (24.6) 2730 (18.7) 1.42 1.29 - 1.56
Penicillin V 259 (8.8) 1162 (8.0) 1.12 0.97 - 1.28
Extended spectrum penicillins 166 (5.7) 559 (3.8) 1.46 1.23 - 1.74
Quinolones 45 (1.5) 153 (1.1) 1.43 1.04 - 1.98
Macrolides 48 (1.6) 150 (1.0) 1.55 1.13 - 2.11
Other systemic antibiotics 206 (8.9) 905 (6.2) 1.47 1.26 - 1.66
Odds ratios estimated through conditional logistic regression modelling.
a See Additional file 4 for anatomical therapeutic chemical codes used to classify systemic antibiotics (J01). b Antibiotics used between July 1st 2005 and January 29th 2008.
Mårild et al. BMC Gastroenterology 2013, 13:109 Page 6 of 9
http://www.biomedcentral.com/1471-230X/13/109treatment and not the treatment per se is associated with
the outcome. Individuals with undiagnosed CD have an
increased risk of several diseases that may, in concert,
increase their likelihood to receive antibiotics [25]. For
example, because antibiotics are frequently misused in
viral infections, [29] confounding may be introduced when
antibiotics are erroneously used to combat adenovirus
or rotavirus infections, both proposed as risk factors for
CD development [2]. However, the Swedish Medical
Products Agency do not recommend antibiotic treatment
in diarrhoeal illnesses, except for cases of severe bacterial
gastroenteritis [30]. Further, just as for diagnosed CD, undiagnosed
CD may be associated with bacterial infections,
[31] which may have also influenced our results. Finally, the
fact that all three cohorts were similarly associated with
antibiotic use raises the possibility that an external factor,
i.e. gastrointestinal symptoms such as diarrhoea, increases
the “risk” of both antibiotic use and the performance of a
small bowel biopsy.
It is well-established that the intestinal microbiota influences
the maturation of the intestinal immune system
[32]. Meanwhile several studies have found an imbalanced
composition of the intestinal microbiota in those with CD
[33]. In vitro studies suggest that intestinal dysbiosis may,
in the presence of gliadin, increase intestinal epithelial
permeability [10] and enable epithelial translocation of
gliadin peptides potentially triggering CD [2]. Other data
suggest that the distinct intestinal microbiota in CD may
have pro-inflammatory properties that affect the immune
response elicited by gluten [34]. Although this study lacks
conclusive evidence for a causal association between antibiotic
use and subsequent CD, our results do not refute the
hypothesis that the intestinal microbiota affects CD development.
A causal association may also be supported by the
slightly stronger association to subsequent CD and certain
antibiotics (e.g., metronidazole) that have a major impact
on the anaerobic bacteria of the colon. Consequently,
today’s prevalent use of antibiotics and their potential
public heath impact on CD development warrant attention
in future research.
Antibiotic use has been associated with the development
of several immunological diseases, including inflammatory
bowel disease [35] and asthma [36]. More importantly
with regard to CD, most [22,37] but not all studies, [38]
have failed to find an association between antibiotic use
and subsequent type 1 diabetes, a disease that otherwise
shares many aetiological traits with CD [39].
A major strength of this study is our use of multiple
groups on the CD spectrum (CD, small-intestinal inflammation
and normal mucosa with positive CD serology)
[18]. With this study design, we were able to examine the
association of antibiotic treatment by the degree of mucosal
abnormality. Multiple groups also improved our evaluation
of potential causality. Another strength is the use of
prospectively recorded exposure and outcome data,
which eliminate the risk of recall bias. Furthermore,
this study provided detailed information on antibiotic
use, including time and age of exposure, type of antibiotics
and number of courses.
The use of biopsy data enabled us to identify a representative
population with CD. In Sweden, more than 95% of
gastroenterologists obtain a small-intestinal biopsy before
CD diagnosis [14], implying that biopsy records have a
high sensitivity for diagnosed CD. We regard the risk of
misclassification in CD as low. In an earlier validation
study 108 (95%) of 114 individuals with villous atrophy
had CD [14]. Misclassification could be more of a concern
in inflammation because villous atrophy may be patchy and
not all inflammation is related to CD or to a pre-coeliac
state. Furthermore, any potential misclassification of histopathology
should be non-differential regarding antibiotic
use and therefore should not lead to spurious associations,
but to an underestimation of the true effect.
Our third cohort included individuals with normal
small-intestinal mucosa, but positive CD serology. Most
of these individuals had a single positive AGA serology
with a lower specificity for CD than TTG or EMA. Thus,
it may be argued that this condition does not represent a
pre-coeliac state. However, when Hill et al. reviewed 26
studies of CD serology, they observed a median AGA
specificity of 93% [40].
Antibiotic exposure was determined by the Swedish
Prescribed Drug Register, which includes nationwide
high-quality data on all dispensed prescribed medications
[19]. Self-medication, i.e. obtaining an antibiotic without
prescription, is very rare in Sweden, estimated to be 0.3%
of all antibiotics used [41]. A limitation of our study is the
recent start of the Swedish Prescribed Drug Register
(established in July 2005) and the left truncation of exposure
data in which individuals diagnosed with CD early
in the study period (and their matched controls) will
have little chance of being classified as antibiotic users
because of lack of antibiotic data before July 2005.
However, this loss of prior antibiotic data should not
be differentially related to future CD status, and therefore
only bias our results toward the null.
Conclusions
In conclusion, we found a positive association between
antibiotic use and subsequent CD, as well as with inflammation,
and with having a normal mucosa but positive CD
serology. One explanation could be that antibiotic exposure,
possibly through changes in the gut microbiota, plays a
role in early CD development, but non-causal explanations
cannot be ruled out. Within the limited time window studied,
the lack of a time-response effect raises the possibility
of reverse causation, in particular, prescription of antibiotics
to individuals with manifestations of undiagnosed CD.
Mårild et al. BMC Gastroenterology 2013, 13:109 Page 7 of 9
http://www.biomedcentral.com/1471-230X/13/109Additional files
Additional file 1: Anatomical therapeutic chemical codes used to
classify systemic antibiotics (J01).
Additional file 2: Odds ratios for prior antibiotic use in individuals
with normal mucosa and positive coeliac disease serology. Odds
ratios (ORs) for prior antibiotic use with adjustment for education level.
Additional file 3: Odds ratios for prior antibiotic use in individuals
with coeliac disease, small-intestinal inflammation, and normal
small-intestinal mucosaa
. Stratified analyses by age at biopsy. Odds
ratios for prior antibiotic use in individuals with coeliac disease. Stratified
analyses by year of diagnosis.
Additional file 4: Odds ratio for prior use of metronidazole in
individuals with small-intestinal inflammation and normal mucosaa
.
Abbreviations
ATC: Anatomical therapeutic chemical (pharmaceutical classification);
AGA: Antigliadin antibody; CD: Coeliac disease; CI: Confidence interval;
EMA: Endomysial antibody; OR: Odds ratio; TTG: Tissue transglutaminase
antibody.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
ICMJE criteria for authorship read and met: KM, WY; BL; PG; MB; TC; JFL.
Agree with the manuscript’s results and conclusions: KM, WY; BL; PG; MB; TC;
JFL. Designed the experiments/the study: KM, JFL. Collected data: JFL.
Analyzed the data: KM. Wrote the first draft of the paper: KM. Contributed to
the writing of the paper: WY; BL; PG; MB; TC; JFL. Contributed to the design
of the study and interpretation of the data analyses: WY; BL; PG; MB; TC.
Interpretation of data; approved the final version of the manuscript: KM, WY;
BL; PG; MB; TC; JFL. Responsible for data integrity: KM, JFL. Supervised the
project including data analyses: JFL. Obtained funding: JFL. All auhtors read
and approved the final manuscript.
Acknowledgements
This work was supported by: The American Scandinavian Foundation [BL],
the Celiac Sprue Association [BL, JFL], and the National Center for Research
Resources, a component of the National Institutes of Health (grant number:
KL2 RR024157) [BL]; National Institutes of Health (grant number:
R01DK090989) [MB], and the Diane Belfer Program for Human Microbial
Ecology [MB]; The Swedish Society of Medicine [JFL], the Swedish Research
Council [JFL], the Sven Jerring Foundation [JFL], the Örebro Society of
Medicine [JFL], the Karolinska Institutet [JFL], the Clas Groschinsky
Foundation [JFL], the Juhlin Foundation [JFL], the Majblomman Foundation
[JFL] and the Uppsala-Örebro Regional Research Council [JFL]. The funders
had no role in study design, data collection and analysis, decision to publish,
or preparation of the manuscript.
Author details
1
Clinical Epidemiology Unit, Karolinska Institutet, Stockholm, Sweden. 2
Astrid
Lindgren Children’s Hospital, Solna, Sweden. 3
Department of Medical
Epidemiology & Biostatistics, Karolinska Institutet, Stockholm, Sweden. 4
Celiac
Disease Center, Department of Medicine, Columbia University Medical
Center, Columbia University, New York, USA. 5
Department of Medicine, New
York University Langone Medical Center, New York, USA. 6
Division of
Epidemiology and Public Health, University of Nottingham, Nottingham City
Hospital, Nottingham, UK. 7
Department of Paediatrics, Örebro University
Hospital, Örebro, Sweden.
Received: 31 January 2013 Accepted: 28 June 2013
Published: 8 July 2013
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doi:10.1186/1471-230X-13-109
Cite this article as: Mårild et al.: Antibiotic exposure and the
development of coeliac disease: a nationwide case–control study. BMC
Gastroenterology 2013 13:109.
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