BACKGROUND: Helicobacter pylori (H. pylori) infection may play a role in Alzheimer's disease (AD).AIM: A prospective, nonrandomized, comparative study was car- ried out to examine the levels of anti-H. pylori-specific IgG antibodies in the cerebrospinal fluid (CSF) and serum of AD patients, compared with those of age-matched cognitively normal controls.PATIENTS: CSF was aspirated from 27 AD patients and 27 age-matched cognitively normal patients with prostate hyperplasia or long-bone fractures necessitating surgery after epidural anesthesia. Serum samples were obtained from AD patients and the day before surgery from controls.METHODS: CSF and serum anti-H. pylori IgG concentrations were measured by means of an enzyme-linked immunosorbent assay.RESULTS: The mean concentration of anti-H. pylori-specific IgG was significantly greater in (a) the CSF of AD patients (10.53 +/- 12.54 U/mL) than in controls (8.63 +/- 8.01 U/mL, p = 0.047), and (b) the serum of AD patients (30.44 +/- 33.94 U/mL) than in controls (16.24 +/- 5.77 U/mL, p = 0.041). CSF anti-H. pylori IgG antibodies correlated with the degree of severity of the disease.CONCLUSION: H. pylori-specific IgG antibody levels are significantly increased in CSF and serum of AD; its titer in CSF might reflect the AD severity, thereby supporting a role for this common infection in the pathobiology of the disease.