Objective The effect of Helicobacter pylori on Barrett’s esophagus is poorly understood. We conducted a meta-analysis to summarize the existing literature examining the effect that H pylori has on Barrett’s esophagus. Design We performed a comprehensive search to identify studies pertaining to the association between H pylori and Barrett’s esophagus. We conducted meta-regression analyses to identify sources of variation in the effect of H pylori on Barrett’s esophagus. Results Our analysis included a total of 49 studies that examined the effect of H pylori on Barrett’s esophagus and 7 studies that examined the effect of cag A positivity on Barrett’s esophagus. Overall, H pylori, and even more so cag A, tended to be protective for Barrett’s esophagus in most studies; however there was obvious heterogeneity across studies. The effect of H pylori on Barrett’s esophagus varied by geographic location and in the presence of selection and information biases. Only 4 studies were found without obvious selection and information bias, and these showed a protective effect of H pylori on Barrett’s esophagus (Relative Risk = 0.46 [95% CI: 0.35, 0.60]). Conclusions Estimates for the effect of H pylori on Barrett’s esophagus were heterogeneous across studies. We identified selection and information bias as potential sources of this heterogeneity. Few studies without obvious selection and information bias have been conducted to examine the effect of H pylori on Barrett’s esophagus, but in these, H pylori infection is associated with a reduced risk of Barrett’s esophagus.

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We conducted an exploratory study to investigate which exposures (including poultry oncogenic viruses) are associated with brain cancer in poultry workers. A total of 46,819 workers in poultry and nonpoultry plants from the same union were initially followed for mortality. Brain cancer was observed to be in excess among poultry workers. Here we report on a pilot case-cohort study with cases consisting of 26 (55%) of the 47 brain cancer deaths recorded in the cohort, and controls consisting of a random sample of the cohort (n = 124). Exposure information was obtained from telephone interviews, and brain cancer mortality risk estimated by odds ratios. Increased risk of brain cancer was associated with killing chickens, odds ratio (OR) = 5.8 (95% confidence interval, 1.2-28.3); working in a shell-fish farm, OR = 13.0 (95% CI, 1.9-84.2); and eating uncooked fish, OR = 8.2 (95% CI, 1.8-37.0). Decreased risks were observed for chicken pox illness, OR = 0.2 (95% CI, 0.1-0.6), and measles vaccination, OR = 0.2 (95% CI, 0.1-0.6). Killing chickens, an activity associated with the highest occupational exposure to poultry oncogenic viruses, was associated with brain cancer mortality, as were occupational and dietary shellfish exposures. These findings are novel.

These results may have important public health implications, since the general population is also exposed to these viruses. Elevated risks were observed for non-poultry-related occupational exposures such as working in a stockyard, working in a chemical plant, use of chemicals to kill moulds, and working in plants where plastic products were manufactured. These preliminary findings indicate that full scale epidemiological studies of adequate statistical power are needed to examine the role of occupational exposures in cancer occurrence in poultry workers.

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