The prevalence of ulcerative colitis is increasing steadily in Japan.
In Western countries, a bimodal distribution, with ulcerative colitis onset peaks in youth and middle age, is observed, and smoking cessation is reported as a risk factor for ulcerative colitis.
However, there are few reports on a bimodal distribution of onset age among Japanese patients.
Dr Haruhiko Takahashi and colleagues from Japan investigated the distribution of onset age and factors related to late onset in ulcerative colitis patients in Japan.
|Late onset was more common among patients diagnosed in 2001 or later|
|Journal of Gastroenterology & Hepatology|
A questionnaire survey of ulcerative colitis patients was conducted to investigate the distribution of the age of onset, and factors that may be related to ulcerative colitis onset in a Japanese university hospital.
Among 465 ulcerative colitis patients, 343 patients responded.
In the distribution of onset age, the research team observed a large peak in patients aged 10–20s, and small peaks were seen at age 40–44 years and then in 50–60s.
The team found that the onset age was older in the ulcerative colitis patients diagnosed in 2001 or later than in those diagnosed in 2000 or earlier.
The researchers noted that late onset was more common among the ulcerative colitis patients diagnosed in 2001 or later, and among former smokers on multivariate analysis.
Dr Takahashi's team concludes, "Similar to ulcerative colitis patients in Western countries, a bimodal distribution of onset age was also observed in Japanese ulcerative colitis patients, and smoking cessation may partly contribute to the increase in late-onset ulcerative colitis patients in recent years in Japan."