Sex-based differences in the incidence of inflammatory bowel diseases-pooled analysis of population-based studies from the Asia-Pacific region.

BACKGROUND: There appear to be differences in risk factor profiles for IBD between Asia-Pacific and Western populations, which might suggest idiosyncrasies in pathogenesis. Recently, sex-based differences in IBD according to the age of diagnosis have been described in Western populations.

AIM: To identify whether sex-based differences in IBD incidence similarly exist across the age spectrum for Asia-Pacific populations.

METHODS: We identified Asia-Pacific population-based cohorts where IBD incidence data stratified by sex were available for the full age spectrum. Cohorts were included only if IBD diagnoses were confirmed and validated. We calculated incidence rate ratios of Crohn's disease (CD) and ulcerative colitis (UC) according to age and compared differences between males and females using random-effects meta-analysis.

RESULTS: Among 567.8 million people from 11 Asia-Pacific countries/provinces/nations, we identified 10 553 incident CD cases (7060 males; 3493 females) and 16 946 incident UC cases (9754 males; 7192 females). Starting in early adolescence until age 50 years, there was a 36%-64% higher incidence of CD in males vs females (P < 0.001). UC incidence ranged from 20%-42% higher in males vs females in the age groups between 15 and 65 years (P < 0.05).

CONCLUSIONS: In a pooled analysis of population-based studies from the Asia-Pacific region, we found a male predominance of both CD and UC for the majority of the age spectrum from adolescence to middle/late-middle age. Additional studies are needed to clarify biological and nonbiological determinants of sex differences in IBD, which might be distinct between Asia-Pacific and Western populations.