The possible causes of the pandemic of peptic ulcer in the late 19th and early 20th century.

Helicobacter pylori is established as a cause of peptic ulcer (PU). Less well recognised is that an epidemic of PU began around the middle of the 19th century, reached a peak at the turn of the century, and is now on the wane. As the epidemic developed, the risk of PU increased in successive generations throughout life. Then the epidemic diminished in successive generations. The risk of gastric ulcer (GU) was highest in people born around 1885, while the risk of duodenal ulcer (DU) was highest in those born about 10-30 years later. H. pylori infection offers an inadequate explanation of the PU epidemic. Although the epidemic coincided with a major rise in cigarette smoking, PU then declined in spite of an increased incidence of smoking. None of the other possible causes of ulcer (non-steroidal anti-inflammatory drugs, stress or diet) satisfactorily explains the epidemics of GU and DU and their asynchronicity. The best, but inadequate, explanation for the epidemic is the coincidence of the acquisition of a new potent strain of H. pylori in childhood and the uptake of smoking in adult life.