People who suffer from irritable bowel syndrome (IBS) are twice as likely to have asthmatic symptoms as well, researchers have discovered.

IBS is a common digestive disorder that produces a range of symptoms including cramp, a feeling of bloating, and a change or disruption of bowel habit, such as constipation or diarrhoea.

The symptoms appear to be due to an increased sensitivity of the bowel, which results in spasm of the bowel muscle. The cause of the disorder is unknown.

Until now IBS has not been associated with respiratory disease in the general population.

The researchers studied the responses of more than 3,000 questionnaires from patients on GP lists in the north of England.

The results, reported in the journal Gut, showed that the prevalence of gastrointestinal symptoms was high, with one in 10 men and one in five women reporting IBS.

More than 13% of men and more 14% of women reported asthmatic symptoms.

Those with confirmed asthma were more than 50% as likely to have IBS.

Both IBS and asthma have previously been linked to acid reflux, a condition in which small amounts of acid from the stomach rise up into the gullet, causing heartburn.

The number of people in the study suffering from IBS, acid reflux and IBS was two-and-a-half times greater than statistical chance.

Underlying cause

Asthma is treated with inhaled steroids

The researchers, lead by Dr Tom Kennedy, of the Department of General Practice, Guy's and St Thomas's Hospital, London, suggest there may be a common underlying disorder responsible for all three condidtions, such as smooth muscle or neuromuscular dysfunction.

A third possibililty is an inflammatory disorder causing both respiratory and gastrointestinal symptoms.

Dr Kennedy said: "It is thought that asthma is caused by an inflammation of the lining of the lung, made worse when the sufferer is exposed to a particular substance.

"It may be that the same inflammation is made manifest in the gut of people suffering from IBS.

Asthma is treated successfully with anti-inflammatory inhaled steriods.

Dr Kennedy said it might be possible to use anti-inflammatory preparations to treat IBS in future.

At present, there is no satisfactory treatment for IBS. A high fibre diet was thought to ameliorate the condition, but recent research has suggested it might exacerbate the symptoms.