The seroepidemiology of Helicobacter pylori and its relationship to chronic atrophic gastritis
There were three main aims to this thesis: 1. to test whether infection with Helicobacter pylori was related specifically to chronic atrophic gastritis (CAG), a precursor of gastric cancer; and to measure the specificity and sensitivity of Helicobacter pylori antibody markers for detecting H.pylori infection of the gastric mucosa; and CAG; 2. to measure the distribution of H.pylori in relation to sociodemographic, dietary and lifestyle characteristics in non-clinical populations from Caerphilly (Wales), Italy, China, and Kenya; 3. to examine the relationship between H.pylori and gastric cancer. H.pylori was strongly associated with CAG and H.pylori antibody level was a sensitive and specific marker of both infection (84.8%, 92.7%) and CAG (71.4%, 90.9%). In Caerphilly and Italy, the prevalence of H.pylori increased steeply to 40-50% in those aged 45-54 years and levelled off in older age groups. In China, over 50% of those aged 35-44 were infected. In Kenya, almost all people studied between 18-30 years were infected with H.pylori. In Caerphilly, H.pylori infection was significantly higher in poorer socioeconomic groups, whilst in Italy, socioeconomic differences with regard to infection were in the same direction but not as pronounced. In Caerphilly, H.pylori infection was related to the number of the subject's siblings but not to the number of children or adults sharing the house of the subject. In Caerphilly, those infected with H.pylori consumed less vitamin C and more alcohol than those not infected. Those infected in Italy consumed more vitamin C but similar amounts of alcohol than those not infected. In China, smoking was inversely related to H.pylori infection. In China, a geographic correlation of +0.34 (2p = 0.02) was found between the prevalence of H.pylori infection (measured in 46 counties) and gastric cancer mortality. There was also a positive (but not significant) correlation with peptic ulcer mortality. No other type of cancer showed a significant association with H.pylori.