A Japanese study of high quality examined 11,657 employees in factories, banks and school. The examiners suspected to have abnormal roentgenologic findings by mass examination were asked to undergo a precise examination by endoscope. The prevalence of gastric ulcers was 2.38% in shift woekers as compared with 1.03% in day workers. For duodenal ulcers, the pravalence were 1.37% and 0.69% for shift workers and day workers, respectively. Thus, the relative risk of duodenal was doubled in shift workers compared with day workers.
In summary, there is strong evidence linking shift work to peptic ulcer disease.