text: Changing demographics of peptic ulcer disease.
  The demography of peptic ulcer changed greatly and uniformly in western countries until the middle of this century. The demographic pattern reversed at about the turn of the century, duodenal ulcer becoming the predominant lesion, males the most often affected, and age-distribution shifting towards senior citizens. These changes have not continued beyond the 1950s, in fact a decline in the incidence of duodenal ulcer has been postulated. Although hospital admission rates have declined dramatically, there is no evidence of a general decline in the 'true' incidence of duodenal ulcer in the population. However, major changes are ongoing, but the pattern differs from country to country. These findings indicate that environmental factors other than those characterizing industrialized societies are actively involved in the etiology of peptic ulcer.