Association of water quality and sewage disposal with Helicobacter pylori incidence in infants

Helicobacter pylori infection is a worldwide health problem, It is a major cause of chronic gastritis, and is strongly associated with peptic ulcer disease and gastric cancer. The infection is generally acquired during childhood, and often remains asymptomatic even in adulthood. Epidemiological studies have shown that higher infection rates occur in developing countries and that lower socioeconomic levels are associated with higher infection frequency.;H. pylori colonizes the human stomach, but it is not known with any certainty how the organism gets from one stomach to another. Evidence supports person-to-person transmission by several different pathways: fecal-oral, oral-oral or gastric-oral, which may vary by a country's level of development. Given that prevalence is higher in developing countries and at lower socioeconomic levels and that access to potable water and a sanitary sewer system are correlated with socioeconomic levels, it seems that a study of water source and sewage disposal would be important in establishing a mode of transmission of infection and provide needed information on the risk factors associated with acquisition of infection.;This dissertation serves to address some of the unknown issues by evaluating water and sewage disposal through a systematic approach, using hypothesis testing, methodological review of the literature, and finally an evaluation of issues related to uncertainty in the measures of outcome. This is accomplished in the following three papers evaluating the association between H. pylori infection rates in children and access to purified water. Paper one utilizes data from an on-going prospective cohort study of infants on the U.S./Mexico border. It tests the hypothesis that access to clean water (and a sanitary sewerage system) reduces the incidence rates of infection in young children. Paper two is a meta-analysis conducted to determine if there is consistency across published reports regarding the association between drinking water and H. pylori infection in children. And paper three is a sensitivity analysis which assesses the potential bias due to outcome measurement error on the estimated effect of drinking water source on rate of infection.