The percentage of people with<unk>  has been determined in Norway and the United States and is similar at 6 to 7.1:100,000. The<unk> 's and Colitis Foundation of America cites this number as approx 149:100,000; NIH cites 28 to 199 per 100,000.<unk>  is more common in northern countries, and with higher rates still in the northern areas of these countries. The incidence of<unk>  is thought to be similar in Europe but lower in Asia and Africa. It also has a higher incidence in Ashkenazi Jews and smokers.<unk>  begins most commonly in people in their teens and 20s, and people in their 50s through to their 70s. It is rarely diagnosed in early childhood. It usually affects female children more severely than males. However, only slightly more women than men have<unk> . Parents, siblings or children of people with<unk>  are 3 to 20 times more likely to develop the<unk> . Twin studies find that if one has the<unk>  there is a 55% chance the other will too. The incidence of<unk>  is increasing in Europe and in newly industrialised countries. For example, in Brazil, there has been an annual increase of 11% in the incidence of<unk>  since 1990.
Crohn's disease
Behçet's disease
Irritable bowel syndrome
Coeliac disease
Ulcerative colitis
Nonsteroidal anti-inflammatory drug
Tropical sprue
Tuberculosis