The prevalence or the number of persons suffering from irritable bowel syndrome (IBS) is complicated. This is mainly because there is lack of clarity of assessment criteria to differentiate between various functional bowel disorders like irritable bowel syndrome, functional bowel diseases like functional esophageal symptoms, functional dyspepsia and abdominal pain. There is also a lack of clarity between differentiating IBS from chronic gastrointestinal disorders.
The Rome criteria and the Manning criteria
One of the most universally used and accepted methods to define IBS is the Rome criteria and the Manning criteria. Many studies use both these criteria to diagnose IBS and assess the prevalence of the disease.
Who does IBS affect?
Studies show that in North America the prevalence of this condition is between 3 and 20% in most studies and an average of 11.6% as assessed from several studies.
Most studies show that a higher ratio of women who develop IBS compared to men. Commonly the ratio is 2:1.
When age of onset of symptoms is assessed from studies, it is seen that IBS symptoms occurred predominantly in patients younger than 45 years and the prevalence of the symptoms of the disease rose again among the elderly.
Geographically surveys in Israel (among Jews not Bedouins), Iran, and India, China etc. have shown low prevalence of IBS. In China for example prevalence is less than 1%.
Prevalence of IBS
Assessing the prevalence of irritable bowel syndrome as per the predominant symptoms or diarrhea or constipation, it was found that the prevalence of IBS with predominant diarrhea was 5.0 to 5.5% where as the prevalence of IBS with predominant constipation was around 5.2 to 5.4%.
The prevalence of IBS with alternating constipation and diarrhea or mixed IBS with 5.2% as assessed from the studies.
Studies from Korea, Greece, Malaysia, Finland and France showed that there is a wide variation in the prevalence of IBS as per the subclassifications.
Prevalence of psychiatric disorders
Studies have also assessed the factors that contribute to development of IBS including depression, anxiety and sleep disorders like insomnia.
The most common psychiatric disorder associated with IBS is depression, with a prevalence of approximately 30% in IBS patients compared to only 18% in normal healthy population.
Anxiety is also commonly encountered as a condition associated with IBS, with 16% affected compared to healthy populations at a rate of 6%.