Helicobacter pylori infection and respiratory diseases: actual data and directions for future studies.

Helicobacter pylori (H. pylori) has been conclusively related to several gastroduodenal diseases. The possible role of the bacterium in the development of extragastric manifestations has been investigated in the past few years. To identify all publications on the association between H. pylori and respiratory diseases, a MEDLINE search of all studies published in English from 1965 to 2013 was conducted. All data are based on case-control studies. Controversial findings of H. pylori seroprevalence have been obtained in patients with bronchial asthma, lung cancer, pulmonary tuberculosis, sarcoidosis, cystic fibrosis, chronic bronchitis and bronchiectasis. At present, on epidemiological bases, there is no definite evidence of a causal relationship between H. pylori infection and respiratory diseases. There is a low consideration of confounding factors as poorer socioeconomic status and tobacco use. The activation of pro-inflammatory cytokines by H. pylori might be a possible pathogenetic mechanism. However, there are no convincing data about the influence of H. pylori on the inflammatory changes of the bronchoepithelium so far. Further studies are needed on the impact of H. pylori eradication, on the prevention, development and natural history of these disorders.