Review Article

The Incidence and Risk Factors for Irritable Bowel Syndrome in Population-based Studies

Francis Creed

Disclosures

Aliment Pharmacol Ther. 2019;50(5):507-516. 

In This Article

Abstract and Introduction

Abstract

Background: In the absence of prior gastrointestinal infection, the risk factors for irritable bowel syndrome (IBS) are not well established.

Aim: To identify the incidence and risk factors for IBS in general population samples

Methods: Narrative review of population-based studies. Electronic databases were searched using the keywords "incidence," "onset," "epidemiology," "population," "risk factors" with "irritable bowel syndrome" with subsequent hand searching. Inclusion criteria were: population-based, adults, prospective design (including retrospective case cohorts), clinical or research diagnosis of IBS and exclusion of individuals who had IBS prior to recruitment.

Results: Of 1963 papers, 38 were included; all provided data on risk factors, 27 reported incidence. The median incidence of physician-diagnosed IBS in 19 general population cohorts was 38.5 per 10 000 person-years (interquartile range = 20-45.3). In 14 cohorts with specific medical disorders, median incidence was 92 per 10 000 person-years (IQR: 73.9-119). Apart from gastroenteritis, the most common risk factors were other medical disorders, female sex, age (both young and old), anxiety and depression, life events/stress, frequent healthcare use, pain and sleep disorders. The results were conflicting for alcohol consumption, smoking and BMI. Incidence rates were similar in different countries but risk factors differed.

Conclusions: Incidence rates were generally lower than previous estimates reflecting physician-diagnosed IBS. The results highlight the importance of other medical and psychosocial problems in the onset of IBS in addition to prior gastrointestinal infections. Aetiological research could be enhanced by studying the underlying mechanisms relating to all of these risk factors.

Introduction

The aetiology of Irritable bowel syndrome (IBS) is unclear and several aetiological models have been proposed.[1–3] Many of these models relate to prior gut infection; the incidence of IBS is approximately 10% after gastroenteritis although this varies by geographical location, infective agent and time since enteritis.[4] The risk factors that emerged from Klem's systematic review of post-infectious IBS incidence included the severity and duration of the enteritis and younger age, female sex, smoking status, anxiety, depression, somatisation and neuroticism.[4] By contrast little is known about the onset of IBS which is not directly associated with recent gastroenteritis.[5–9] The aim of this review is to identify what is currently known of the incidence and risk factors for developing new onset IBS in population-based cohorts to complement what is already established regarding post-infectious IBS. In the absence of such knowledge, many reviews of IBS rely on prevalence data to support aetiological theories when only prospective studies can demonstrate causality as opposed to associations.[10]

Few prospective studies have been performed.[2,11] One review quoted four prospective studies and estimated the incidence of IBS in the population to be around 1.5% per year by questionnaire and 2-2.6 per 1000 per annum for clinically diagnosed IBS.[1] One systematic review confirmed anxiety and depression as risk factors for post-infectious IBS but only three studies were population based and, in these, anxiety and depression appeared to be weaker risk factors compared to the year after a GI infection.[12]

The current study reviewed studies that demonstrated the incidence of IBS in population-based cohorts of adults and provided data indicating the risk factors for new onset IBS.

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