Epidemiological trends in stomach-related diseases.

Epidemiology is a study of disease variations by geography, population demographics and time. Temporal influences can manifest themselves as age effects, period effects, cohort effects, seasonal or monthly variations. The acquisition of Helicobacter pylori infection during early childhood and the ensuing risk for the future development of peptic ulcer or gastric cancer represents a typical example for a cohort effect in digestive diseases. The incidence and prevalence of uncomplicated peptic ulcer have decreased in recent years, largely because of the availability of treatment to eradicate H. pylori and the decreasing prevalence of H. pylori infection. Nowadays, gastric and duodenal ulcers tend to occur in older people, who were more likely to have been exposed to H. pylori in their childhood than recently born generations. The overall incidence of gastric cancers is declining; however, there has been a relative increase in the incidence of tumors of the esophagogastric junction and gastric cardia. Thus, by extrapolating the strong, stable and consistent mortality rate declines in recent decades, gastric cancer was projected to become increasingly less important as a cause of death in Europe in the next decades.