[Catalyst 2017]

BY MAHESH KRISHNA
Iam a first generation American, as
both of my parents immigrated here
from Myanmar, a third world country.
There had been no occurrence of any
Inflammatory Bowel Disease (IBD) in my
family, yet I was diagnosed with Ulcerative
Colitis at the beginning of my sophomore
year of high school. Since IBD is known
to be caused by a mix of genetic and
environmental factors, 1, 2 what specifically
triggered me to develop Ulcerative
Colitis? Was it the food in America, the
air I was exposed to, a combination of
the two, or neither of them at all? Did
the “environment” of the first world in
the United States cause me to develop
Ulcerative Colitis?
IBD is a chronic autoimmune disease,
characterized by persistent inflammation
of the digestive tract and classified into
two separate categories: Ulcerative Colitis
and Crohn’s Disease. 3 Currently, there is no
known cure for IBD, as its pathogenesis (i.e.
the manner in which it develops) is not fully
understood. 1 Interestingly, the incidence
of IBD has increased dramatically over
the past century. 1 A systematic review by
Molodecky et al. showed that the incidence
rate of IBD was significantly higher in
Western nations. This may be due to better
diagnostic techniques or the growth of
environmental factors that promote its
development. This could also suggest that
there may be certain stimuli in first world
countries that can trigger pathogenesis in
individuals with a genetic predisposition to
IBD.
Environmental factors that are believed to
affect IBD include smoking, diet, geographic
location, social status, stress, and
microbes. 1 Smoking has had varying effects
on the development of IBD depending on
the form; smoking is a key risk factor for
Crohn’s Disease, while non-smokers and
ex-smokers are usually diagnosed with
Ulcerative Colitis. 4 There have not been
many studies investigating the causal
relationship between diet and IBD due to
the diversity in diet composition. 1 However,
since IBD affects the digestive system, diet
has long been thought to have some impact
on the pathogenesis of the disease. 1 In
first world countries, there is access to a
larger variety of food, which may impact the
prevalence of IBD. People susceptible to the
disease in developing countries may have a
smaller chance of being exposed to “trigger”
foods. In addition, IBD has been found in
higher rates in urban areas versus rural
areas. 1,4, 5 This makes sense, as cities have
a multitude of potential disease-inducing
environmental factors including pollution,
poor sanitation, and microbial exposure.
Higher socioeconomic status has also been
linked to higher rates of IBD. 4 This may be
partly due to the sedentary nature of white
collar work, which has also been linked
to increased rates of IBD. 1 Stress used
The Hygiene Hypothesis
states that the lack of
infections in western
countries is the reAson
for an increasing
amount of autoimmune
and allergic diseases.
The idea behind the theory
is that some infectious
agents guard against a
wide variety of immunerelated
disorders.
to be viewed as a possible factor in the
pathogenesis of IBD, but recent evidence
has indicated that it only exacerbates the
disease. 3 Recent research has focused on
the microorganisms in the gut, called gut
flora, as they seem to have a vital role in
the instigation of IBD. 1 In animal models, it
has even been observed that pathogenesis
of IBD is not possible in a germ-free
environment. 1 The idea of the importance
of microorganisms in human health is also
linked to the Hygiene Hypothesis.
The Hygiene Hypothesis states that the
lack of infections in western countries is
the reason for an increasing amount of
autoimmune and allergic diseases. 6 The idea
behind the theory is that some infectious
agents guard against a wide variety of
immune-related disorders. 6 Animal models
and clinical trials have provided some
evidence backing the Hygiene Hypothesis,
but it is hard to causally attribute the
pathogenesis of autoimmune and allergic
diseases to a decrease in infections, since
first world countries have very different
environmental factors than third world
countries. 6
The increasing incidence of IBD in
developed countries is not yet fully
understood, but recent research points
towards a complex combination of
environmental and genetic factors. The
rise of autoimmune disease diagnoses
may also be attributed to better medical
equipment and facilities and the tendency
of people in more developed countries to
regularly get checked by a doctor. There
are many difficulties in researching the
pathogenesis of IBD including isolating
certain environmental factors and obtaining
tissue and data from third world countries.
However, there is much promising research
and it might not be long until we discover a
cure for IBD.
Works cited
[1] Danese, S. et al. Autoimm Rev 2004, 3.5, 394-400.
[2] Podolsky, Daniel K. N Engl J Med 2002, 347.6,
417-29.
[3] Mayo Clinic. “Inflammatory Bowel Disease (IBD).”
http://www.mayoclinic.org/diseases-conditions/
inflammatory-bowel-disease/basics/definition/con-
20034908 (accessed Sep. 30, 2016).
[4] CDC. “Epidemiology of the IBD.” https://www.
cdc.gov/ibd/ibd-epidemiology.htm (accessed Oct.17,
2016).
[5] Molodecky, N. et al. Gastroenterol 2012, 142.1, n.
pag.
[6] Okada, H. et al. Clin Exp Immuno 2010, 160, 1–9.
Design by Juliana Wang
EDITED by Carolina Hatanpaa
36 | CATALYST