Inflammatory bowel disease (IBD) is a chronic, relapsing, inflammatory disorder of
the gastrointestinal tract, and includes UC and CD. IBD results from a combination
of genetic susceptibility, environmental exposure, and dysregulated response to intestinal
microbiota.1 The incidence and prevalence of IBD has been increasing worldwide and
appears to be highest in North America and Europe.1 Despite its previously low incidence,
Asia has experienced a significant increase in IBD in the past two decades, while
Europe has seen a plateau or even a decreasing incidence.1 The highest incidence of
IBD in Asia has been reported from East and South Asian countries of China, Japan,
South Korea, and India.1 With the plateau of IBD incidence in several Western countries
and rising incidence in Asian countries, the geographic landscape of IBD may be rapidly
changing.
In a systematic review on the epidemiology of IBD, Molodecky et al.2 reported the
United States and Sweden among the countries with the highest occurrence of IBD. They
also reported China, Japan, South Korea, and India among the countries with the lowest
occurrence of IBD.2 Despite the data on the prevalence and incidence of UC and CD,
the estimated current disease burden of these diseases in various Asian countries
in comparison to Western countries is not clear. We aimed to estimate the disease
burden of UC and CD in these six countries, with 2010 as the reference year.
We searched PubMed with keywords “Ulcerative colitis,” “Crohn's disease” or “Inflammatory
bowel disease,” and “incidence” or “prevalence.” Each was cross-referenced with the
six countries mentioned above. The study with the most recent data on prevalence and
incidence of CD and/or UC was selected for each country. Wherever possible, a population-based
study was selected to estimate both prevalence and incidence. If population-based
data were not available, the latest hospital-based study was used. Prevalence and
annual incidence was derived from each of the selected studies.3
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12 The census data from each country were used to estimate their national population
in the year of the prevalence study. Available data on prevalence was superimposed
on the national population at the time of the study to estimate the disease burden
of CD or UC.3
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12 Data on incidence rates were used to calculate the new cases of UC or CD since
the last prevalence study.7
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12 For most of the selected countries, the rate of increase in annual incidence of
UC and/or CD is not known; thus, to maintain uniformity, the incidence was assumed
to be stable since last reported. The most current annual incidence rates available
were superimposed on the national population at the time of the latest prevalence
study to calculate the number of patients newly diagnosed with UC or CD every year.3
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12 This was then multiplied by the number of years between the last prevalence study
and 2010 to calculate the newly diagnosed cases of CD or UC between the last prevalence
calculation and 2010. The total national disease burden of UC and CD in 2010 was calculated
by adding this number of newly diagnosed cases of CD or UC to the baseline national
disease burden at the time of the latest prevalence study.
The estimated disease burden in 2010 for India was 1.1 million patients with UC, as
compared to 0.8 million in the United States and 0.5 million in China. The estimated
burden of UC patients in the other above mentioned countries is detailed in Table
1.
In 2010, the estimated number of patients with CD in the United States was about 0.8
million. This is much higher compared to the CD burden in China (0.09 million), Japan
(0.03 million), Sweden (0.02 million), and South Korea (0.01 million). There are no
prevalence and/or incidence studies on CD in India, but hospital-based studies have
shown that for every four cases of UC, at least one CD case is detected in India.13
14 Thus, the presumed burden of CD in India in 2010 was about 0.3 million.
Among the six countries studied, the United States appears to have the highest burden
of IBD patients (1.6 million), closely followed by 1.4 million in India. The disease
burden of other countries is summarized in Table 1.
Our analysis shows that despite being considered countries with low occurrence of
UC and CD, many Asian countries have substantially higher numbers of IBD patients
compared to Western countries considered to have high occurrence of IBD. The prevalence
of UC in India (44.3 per 100,000) is much lower than that in the United States (286.3
per 100,000) or Sweden (350 per 100,000).5
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7 Moreover, the incidence of UC in India (6.02 per 100,000) is much lower than the
UC incidence in United States (8.8 per 100,000) and Sweden (20 per 100,000).7
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16 However, because of its population size, India has a much higher disease burden
of UC compared to other countries with much higher incidence and prevalence of UC,
including the United States and Sweden. The disease burden of CD appears to be highest
in the United States, with about 0.8 million CD patients. We estimate that there are
about 0.3 million CD patients in India. Interestingly, despite much lower CD incidence
and prevalence compared to Sweden, China, and Japan have a burden of CD almost 4.5
times and 3 times higher, respectively.
Thus, India has the highest burden of IBD in Asia and one of the highest in the world.
Despite the low prevalence and incidence of IBD, Asian countries might have a significantly
higher burden of IBD patients compared to Western countries. While the incidence and
prevalence of IBD have stabilized in North America and Europe, both continue to rise
in low-incidence regions such as Eastern Europe, Africa, and Eastern and Southern
Asia.1
16 This changing epidemiology of IBD over time and geography suggests that environmental
factors play a major role in pathogenesis. Changes in lifestyle in developing countries
have resulted in more “Westernized” diets, leading to higher consumption of fatty
acids, refined sugars, and fast food and less consumption of fruits, vegetables, and
fiber.17
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19 Urbanization of societies leading to improved hygiene status, change in microbial
exposure, and antibiotic use could also be contributing to the pathogenesis.1
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18 In addition, the susceptibility genes for IBD appear to be different among Western
and Asian countries.18 This rising incidence of IBD in developing countries gives
us a novel chance to explore the genetic and environmental factors underlying the
pathogenesis of IBD.
Increasing disease burden of IBD among developing countries raises several concerns.
First, it is unclear whether healthcare systems in these countries are prepared to
deal with the burden. Clearly, the disease burden of IBD in several Asian countries
is much higher than we expected, and in many of these regions, IBD is still considered
rare, leading to frequent underdiagnosis or misdiagnosis.1
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18 Epidemiological studies from the majority of developing countries are lacking,
making it difficult to estimate the exact burden of UC and/or CD in several Asian
countries. Well-designed pannational epidemiological studies covering both rural and
urban settings, along with regions with varied ethnicities, are much needed. There
is also a need to increase awareness among healthcare providers on the appropriate
diagnosis of IBD in countries with high background prevalence of infections, especially
tuberculosis. Use of biologics in developing countries is limited due to high cost
and high prevalence of infections such as tuberculosis.18 The major significance of
the awareness of the high disease burden of IBD in India is that it outlines the urgent
necessity for an adequate number of health care providers, facilities for diagnosis
and treatment of a massive patient load, and sensitization of health care agencies
to promote research on cost-effective methods of therapy. Despite one of the highest
disease burdens of IBD in the world, India has one of the most deficient public health
insurance systems in Asia.19 As most Indian patients end up paying for their medical
expense, only a minority of patients who need expensive therapies such as biologics
can afford them.19
Our study also had several limitations. First, the disease burden in our study is
only a close estimation of the exact number, as we have used prevalence and incidence
rates in our calculation that are based on studies limited to a particular geographic
region, and are not pan-national. Second, we used the last available incidence rates
for our calculation, which might have led to underestimation of the disease burden,
given the fact that available studies suggest rising incidence of IBD in some Asian
countries. However, recent studies from South Korea suggest that the incidence might
also be plateauing in other Asian countries.1 In addition, several prevalence and
incidence values have been estimated from hospital-based studies. For example, there
are no population-based prevalence studies on UC from China; thus, we used the hospital-based
study by Chow et al.8 In addition, the number of new cases diagnosed since the last
prevalence study was calculated used the baseline population at the time of prevalence
calculation, and did not take into account population growth since then. Thus, the
disease burden estimation in countries such as India, where the population is growing
rapidly, is likely an underestimation.
In conclusion, the disease burden of IBD in developing countries is much higher than
in the developed world. It is imperative that their healthcare systems be prepared
for this challenge.