Global Incidence of Gastric Cancer by Age and Subtype with Age-Period-Cohort Analysis from 1988 to 2017 and Predictions to 2032.

Background: Globally, gastric cancer incidence trends and risk factors vary by age group and subtype, cardia gastric cancer (CGC) and non-cardia gastric cancer (NCGC). However, in-depth temporal studies are lacking.

Methods: Using data from Cancer Incidence in Five Continents volumes VII to XII for 25 countries, we applied the joinpoint regression to assess trends in the age-standardized incidence rate. The age-period-cohort analysis yielded cohort effects, and the Bayesian age-period-cohort analysis generated predictions.

Results: We observed declines in NCGC incidence and cohort effect between 1988 and 2017 in most countries. However, increasing trends in subpopulations in China, the United States, and New Zealand warrant attention. Notably, NCGC incidence among females under the age of 50 years (defined as the "young population" in this study) was higher than for males in 22 countries, which is contrary to previous reports showing a higher incidence in males in the whole population. CGC incidence trends were diverse, with notable increases in the overall and/or younger populations in some countries. Projections to 2032 suggest that CGC and NCGC incidences will converge, notably in males across 12 countries-nine for the whole male population and 10 for the young males.

Conclusions: Long-term incidence trends of CGC and NCGC, combined with cohort effects, reveal global shifts in incidence and risk factors, with an increasing incidence of CGC and higher NCGC rates in young females compared with males.

Impact: This study underscores changing gastric cancer trends in young populations, emphasizing the need for targeted screening and risk factor investigation.