Stomach cancer incidence trends in selected Latin America countries: Age, period, and birth-cohort effects.

BACKGROUND

to explore the age, period, and birth-cohort effects on stomach cancer incidence trends during 3 decades in selected Latin American countries.

METHODS

a time-trend study was performed using Cancer Incidence in Five Continents data from high-quality population-based cancer registries(PBCRs) in Latin American countries. Crude and age-standardized incidence rates(ASRIs) were calculated. Time trends in ASRIs were assessed using the average annual percentage change(AAPC). Age-period-cohort effects were estimated by Poisson regression for individuals aged between 20 and 79 years with stomach cancer informed by PBCRs from 1983 to 2012 in Cali(Colombia); from 1982 to 2011 in Costa Rica; and from 1988 to 2012 for Goiania(Brazil) and Quito(Ecuador). The goodness-of-fit model was tested using the deviance of the models.

RESULTS

a decrease in age-standardized incidence rates was observed for both genders in all populations covered by PBCRs, except for young men from Cali(AAPC 3.89 95 %IC: 1.32-7.29). The age effect was statistically significant in all areas, and the curve slope reached peaks in the older age groups. The cohort effect was observed in all PBCRs. Regarding the period effect, an increased ratio rate was observed for both genders in Costa Rica(1997-2001 women RR 1.11 95 %CI: 1.05-1.17; men RR 1.12 95 %CI: 1.08-1.17) and Goiânia(2003-2007 women RR 1.21 95 %CI: 1.08-1.35; men RR 1.09 95 %CI: 1.01-1.20), while Quito(1998-2002 women RR 0.89 95 %CI: 0.81-0.98; men RR 0.86 95 %CI: 0.79-0.93) presented a decrease.

CONCLUSION

the present study showed a decreasing gastric cancer trend for over the past 30 years with gender and geographic variations. Such a decrease seems to be mainly a result of cohort effects, suggesting that the economic market opening process led to changes in the risk factor exposures over successive generations. These geographic and gender variations may reflect cultural/ethnic/gender differences and differences in dietary and smoking rate patterns. However, an increased incidence was observed for young men in Cali, and additional studies are needed to determine the cause of the increasing incidence in this group.