Epidemiology

IBS is present in 10% to 15% of adults in the US, and is the most common cause for referral to gastroenterologists, accounting for up to 50% of referred patients.[4][5][6] In the UK, it is estimated that the prevalence is between 6.1% and 21.6%, with a higher prevalence in women than men.[7][8][9] The prevalence of IBS is similar in Europe and is lower, but increasing, in the Asia-Pacific region.[10] Reports from Africa vary, but prevalence rates as high as 33% have been reported.[10]

In Australia, a postal questionnaire (4500 people aged ≥18 years) showed prevalence of IBS according to Manning, Rome I, and Rome II criteria to be 13.6%, 6.9%, and 4.4%, respectively.[11] Equivalent types of postal surveys conducted in Asia found similarly lower IBS prevalence rates in Singapore (11.0%, 10.4%, and 8.6% according to Manning [>1 criteria], Rome I, and Rome II criteria, respectively) and in China (11.5%, and 5.7% according to Manning and modified Rome II criteria), this last one showing a higher prevalence in women.[12]

One review reported a median incidence of physician-diagnosed IBS of 38.5 per 10,000 patient-years.[13]

Among adults who seek medical help, women outnumber men at a ratio of 2:1.[14] Symptoms of IBS can begin in adolescence or early adulthood, but the onset of symptoms after age 50 years is unusual.[15][16]

One study conducted in a health maintenance organisation population in the US showed the prevalence of IBS symptoms in respondents to be 19.5%.[17]

In one systematic review, the pooled prevalence of IBS in population-based studies that used the Rome III criteria was greater than that in studies employing Rome IV criteria (9.2% vs. 3.8%, respectively).[18] Mixed IBS (IBS-M) was the most common subtype with the Rome III criteria.

Familial aggregation of IBS has been reported; the odds of having IBS increase (odds ratio 2.75) if a first-degree relative has IBS.[19] A history of physical or sexual abuse has been reported in 32% to 44% of patients with IBS.[20][21][22] Endometriosis may be a risk factor, with one meta-analysis showing a threefold increased prevalence of IBS in women with endometriosis, compared with women without the condition.[23] IBS symptoms may also develop following enteric infections.[24]

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