Irritable bowel syndrome hits women twice as often in the West, but not everywhere
Irritable bowel syndrome affects roughly one person in nine worldwide, yet its pattern shifts with geography. In Western countries women get it about twice as often as men. In East Asia that gap vanishes, and in South America, South Asia and Africa men are affected at least as often. Nobody fully knows why.
Irritable bowel syndrome is classed as a functional disorder, meaning the gut misbehaves without visible damage. Typical features are abdominal pain, bloating and shifting bowel habits, often arriving as attacks that fade within a day and then return. By definition symptoms must have persisted for at least six months. Doctors diagnose it by ruling out look-alikes such as celiac disease and inflammatory bowel disease, and certain alarm signs, including onset after 50, weight loss or blood in the stool, point toward something else. It does not shorten life or lead to other serious diseases.
The condition has a long paper trail. It was first described in 1820, and the present name came into use in 1944. Estimates of how common it is range wildly between countries, from 1.1 to 45 per cent, partly because definitions differ, with an average across the globe of 11.2 per cent. It appears to become less frequent with age.
Its causes remain uncertain, but a leading idea is that the whole gut-brain axis, the two-way signalling between the digestive tract and the nervous system, is disturbed. Stress systems, including the hormonal loop running from the hypothalamus to the adrenal glands, behave abnormally in many patients, and anxiety or psychiatric illness comes before gut symptoms in about two-thirds of cases.
Infection is another trigger. A bout of gastroenteritis raises the risk of developing the syndrome six-fold, and about 10 per cent of cases begin this way. One proposed mechanism is molecular mistaken identity: bacteria causing the infection make a toxin called CdtB, and antibodies against it can cross-react with vinculin, one of the body's own proteins. Gut microbes differ too, with some groups more abundant and others, such as Bifidobacteria and Lactobacillus, less common than in healthy people.
Source: Irritable bowel syndrome
