BACKGROUND: Although serological findings indicate the presence of a relationship between Helicobacter pylori (HP) and vascular disease, no data have been reported about a possible association of HP with dementia. The aim of the present study was to determine whether chronic HP infection might play a role in Alzheimer's disease (AD). METHODS: Plasma homocysteine level, serum folate and vitamin B(12) concentrations, plasma pyridoxal phosphate level, IgG and IgA antibodies to HP, and C-reactive protein (CRP) were determined in 30 AD patients, 30 patients affected by vascular dementia (VaD), and 30 control subjects. All patients and control subjects were matched for age, educational level, and nutritional and socioeconomic status. None of the subjects had a history of chronic gastritis, peptic ulcer, gastric cancer, or major abdominal surgery. RESULTS: HP-IgG level was significantly increased in VaD patients as compared to controls and AD patients, while AD patients had HP-IgG levels higher than those of normal controls. HP-IgA levels were equally increased in both VaD and AD patients. CRP was higher in AD patients than in VaD patients and controls, although CRP levels in VaD patients were also significantly increased. CONCLUSIONS: The present study found an association between HP infection and AD. The question remains as to whether this association is due to the ubiquity of HP, or whether it contributes to the neuroinflammatory process in AD. The relationship between HP and AD, if confirmed by additional studies with a greater number of patients, may have important clinical and therapeutic implications.