People with irritable bowel syndrome (IBS) were three times as likely as people without the condition to have a relative who also had the disorder, Dr Yuri A. Saito of the clinic's Miles and Shirley Fiterman Center for Digestive Disease in Rochester, Minnesota, and her colleagues found.
IBS may affect up to 30% of the general population. Symptoms can include abdominal pain, diarrhoea, bloating and constipation. It's not clear what causes the condition, although severe gastrointestinal infections may increase IBS risk.
While past studies have suggested that family members of people with IBS are at increased risk of the disease themselves, these investigations have relied on patients' own reports of their relative's symptoms.
And since these symptoms aren't matters for dinner table conversation in most families, Saito noted, many patients may be unaware that a relative is also suffering from the syndrome.
How the study was done
In the current study, Saito and her team directly surveyed 477 people with IBS and 1 492 of their first-degree relatives (meaning a parent, sibling or child), as well as 297 healthy control patients and 936 of their relatives, about their bowel symptoms.
Half of the IBS patients' family members had symptoms themselves, compared to 27% of the control patients' families. This translated into a 2.75 times greater risk of IBS for patients' family members.
Saito said she hopes the findings will kick-start a hunt for genes that might be involved in IBS; right now, she noted, none have been discovered.
Environmental factors shared within families could also be a factor too, the researcher pointed out; for example, people who have been abused are at increased risk. While the findings have no treatment implications for people struggling with IBS right now, the researcher added, it may be "reassuring" for them to know that their symptoms have some biological cause.
"I think a lot of people ask themselves, 'why me,' and a lot of times we don't have a good answer to that," she said. "We don't know exactly what it is yet, but we're working on it." - (Reuters Health, March 2010)