1.2　Age and Gender

Gender differences exist in chronic pancreatitis，and the majority of patients were male.The seventh nationwide epidemiological study of CP in Japan reported the sex ratio（male/female）of the patients with CP was 4.6（Hirota et al.2014）.James estimated between 73%and 91%of CP patients were male based on previous studies（Jupp et al.2010；Wang et al.2009；Levy et al.2006；Lankisch et al.2002b；Garg and Tandon 2004；Wehler et al.2004）.The gender distribution of CP is related with etiological factors.Men are more likely to have Alcohol-related pancreatitis than women，but the gender differences decrease with the rising alcohol consumption among women（Muniraj et al.2014；Yadav and Lowenfels 2013）.Pancreatitis is more associated with gallstones，endoscopic retrograde cholangiopancreatography（ERCP），autoimmune diseases，or to be idiopathic among women（Yadav and Lowenfels 2013）.(https://www.daowen.com)

Chronic pancreatitis is more common among persons who are between 40 and 60 years old.The mean age of the CP patients varied with geographical region and time based on the previous studies.A study in England and Wales described the hospital admissions for chronic pancreatitis peaked in those aged between 35 and 54 years（Tinto et al.2002）.A prospective nationwide survey among 1086 subjects in India reported the mean age of patients was 39.7 years（Balakrishnan et al.2008）.The mean age of CP patients in a retrospective multicenter survey from 22 hospitals in China was 48.90 years（Wang et al.2009）.The average age of CP patients was 47.80 years for both men and women in the 1960s，and it increased to 57.6 years for men and 60.2 years for women in the 1990s in Japan（Jupp et al.2010；Garg and Tandon 2004）.The data from the sixth nationwide epidemiological survey in Japan in 2007 showed the mean age of males and females with definite and possible CP was 59.3 and 60.2 years，respectively（Hirota et al.2012）.In the seventh survey conducted in Japan in 2011，the mean age increased to 62.2 years in males and 63.3 years in females（Hirota et al.2014）.