Epidemiological characteristics of inflammatory bowel disease in Bologna, Italy--incidence and risk factors.

Recently, in Bologna, an inflammatory bowel disease incidence of 7.7/10(5)/year has been calculated, about one third of that reported in Northern Europe, confirming the existence of a 'North-South gradient'. A first peak of incidence was observed at 20-29 years of age and a second peak at 60-69 years of age for ulcerative colitis (UC) alone. A prevalence of UC males, mainly after the 7th decade, and of Crohn's disease (CD) females in the first peak was found. A greater frequency of ex-smokers in UC, with a relative risk (RR) significantly higher in males for all age groups (RR = 6.1; p < 0.01) and of smokers in CD with a RR significantly higher in 20- to 29-year-old females (RR = 11.6; p < 0.05) was observed. A different pattern for the two diseases exists: male ex-smokers and young female smokers are at risk of developing UC and CD, respectively.