Helicobacter pylori infection and dementia: can actual data reinforce the hypothesis of a causal association?

Helicobacter pylori (H. pylori) is involved in the development of several gastroduodenal diseases. Since the latest decade, several studies have reported on the link between chronic H. pylori infection and a variety of extragastric manifestations, including dementia. To identify the publications on the association between H. pylori and dementia, a MEDLINE search was conducted. Although case-control studies reported controversial data, a recent longitudinal population-based cohort study found that after 20 years of follow-up, 28.9% of H. pylori-positive versus 21.1% of H. pylori-negative subjects developed dementia. After correction for confounding factors, the infection was significantly associated with higher risk of developing dementia (P=0.04). Moreover, in another study evaluating the effect of H. pylori eradication on the progression of dementia in Alzheimer's disease patients with peptic ulcer, the cure of the bacterium was associated with a decreased risk of dementia progression compared to persistent infection. To date, defining H. pylori as a target for prevention or treatment of dementia remains a topic with much controversy but of essence, as any relationship would reduce, due to the cost-effectiveness of the therapy, a burden on the National Health Care budget. The need for extensive studies with appropriate epidemiological and clinical approaches is crucial to investigate a potential causal relationship.