Crohn's disease - Risk factors

The development of inflammatory bowel diseaseA group of inflammatory conditions of the intestine. The two major forms are Crohn’s disease and ulcerative colitis. (IBDAn abbreviation for inflammatory bowel disease, a group of inflammatory conditions of the intestine. The two major forms are Crohn’s disease and ulcerative colitis.) seems to be caused by a combination of factors including genetics, which is your inherited predisposition, along with ethnic origin, your environment, diet and lifestyle.

Genetic factors

IBDAn abbreviation for inflammatory bowel disease, a group of inflammatory conditions of the intestine. The two major forms are Crohn’s disease and ulcerative colitis. can be hereditary. If you have a relative with Crohn's disease, especially in your immediate family, you are at greater risk of developing it yourself. The first geneThe basic unit of genetic material carried on chromosomes. associated with Crohn's disease, named NOD2, was discovered in 2001. A mutationA change in the genetic material (DNA) of a cell, or the change this this causes in a characteristic of the individual, which is not caused by normal genetic processes. of this geneThe basic unit of genetic material carried on chromosomes. increases a person's risk by 25 per cent. At least five other genes may also be involved.

Environmental factors

Substances in the environment, such as bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell., chemicals or pollen, have the potential to trigger the body's defence systems. These substances are known as antigens. Such a reaction could lead to uncontrolled inflammationThe body’s response to injury. in the gastrointestinal tractThe gut, which begins at the mouth and ends at the anus..

Geography

Crohn's disease is more common in North America and northern Europe than in other parts of the world, such as Asia or Africa.

Age

Crohn's disease can occur at any age, but symptoms are usually first seen between the ages of 20 and 40 years.

Diet

There is much debate about whether certain foods increase the risk of developing Crohn's disease. Some small scientific studies have suggested that a high intake of meat and fatty and sugary foods may increase the risk, at least in childhood, whereas foods such as vegetables, fruits, olive oil, fish, and fibre may reduce it.

However some doctors think that diet has no effect on the risk of developing the disease, but rather can affect the symptoms. This topic is the subject of ongoing research.

Smoking

Smoking increases the risk of developing Crohn's disease, especially among people with a family history. Smoking may also make symptoms worse or reduce the effectiveness of treatment if you have been diagnosed with Crohn's disease.

Medications

Past use of antibioticsMedication to treat infections caused by microbes (organisms that can't be seen with the naked eye), such as bacteria. may be associated with the development of Crohn's disease, but it is not known whether or not these medications actually increase the risk of this condition.

Nonsteroidal anti-inflammatoryAny drug that suppresses inflammation drugs (NSAIDsA group of drugs that provide pain relief and reduce inflammation. ) can cause flare-upsTerm to describe episodes when the symptoms of a condition worsen. of Crohn's disease and may slightly increase the risk of its development, although again, the evidence is not clear.

Women taking oral contraceptives may also be at higher risk. However, this risk has largely disappeared with the introduction of the minipill.

Infections

Scientists believe that one or more infectious agents may be involved in the development of Crohn's disease, perhaps because some people with a geneticRelating to the genes, the basic units of genetic material. susceptibility have impaired body defences or altered responses to certain microorganismsOrganisms that are too small to be seen with the naked eye, such as bacteria and viruses..

One possibility is a bacterium called Mycobacterium avium subspecies paratuberculosis (MAP), which causes a similar disease in cattle. Researchers are investigating whether treatment for this infectionInvasion by organisms that may be harmful, for example bacteria or parasites. could help patients with Crohn's disease. It is not yet clear whether MAP could initiate Crohn's disease in susceptible people when they drink infected milk.

Other organisms have also been associated with Crohn's disease, such as a type of E. coli which is often found in the lining of the small intestineThe section of gut, or gastrointestinal tract, from the stomach to the anus. in people with Crohn's disease.