Gastric Cancer Mortality Trends in the Southern Cone: Disentangling age, period and cohort patterns in Argentina and Chile.

Although Argentina and Chile are neighboring countries, gastric cancer (GC) is the first cancer death cause in the Chilean male population, while it is ranked in fifth place for Argentinean males. This study is the first to identify the differential time-patterns associated with the age-period-cohort effects for the last few decades (1990-2015) in these Southern Cone countries. Trends of age-standardized truncated mortality rates (ASMR) for GC were analyzed using log-linear Poisson age-period-cohort models, including cubic splines for each component. The ASMR trends for GC decreased in both sexes but more considerably in Chile and more favorably for males (annual percentage changes 2002-2015 = -3.5, 95%CI: -3.9 to -3.1). Moreover, GC age-specific mortality rates were noticeably higher in Chile. A favorable decreasing mortality risk throughout the periods (from 2000) and by cohort was observed for both countries; however, the risk reduction has stabilized in younger female cohorts since 1950-cohort. In conclusion, overall favorable decreasing trends for GC mortality were found; however, when age-period-cohort effects were disentangled, Chile and younger female cohorts showed a more unfavorable scenario. Obesity, lifestyles, and environmental conditions (like altitude) may explain country differences. This analytical approach may be a valuable tool to be replicated in other countries with no population-based cancer registries and acceptable mortality data quality.