Study: Stomach Bacteria Linked With Higher Risk of Alzheimer Disease


Those who were exposed to the clinically acquired stomach bacteria had a 24% increased risk of Alzheimer disease after a decade of onset.

Helicobacter pylori has been linked with a higher risk of Alzheimer disease (AD), according to results of a study published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.1,2 The risk of AD was approximately 24% after a decade of onset of clinically acquired H. pylori infection (CAHPI), according to the study authors.3

“Given the global aging population, dementia numbers are expected to triple in the next 40 years. However, there remains a lack of effective treatment options for this disease,” Paul Brassard, MD, MSc, a professor in the Department of Medicine at McGill University. “We hope the findings from this investigation will provide insight on the potential role of H. pylori in dementia in order to inform the development of prevention strategies, such as individualized eradication programs, to reduce infections at the population level.”1

H. pylori has been decreasing in prevalence worldwide, with the biggest risk factors in America being male, poor adherence or difficult access to treatment, or lack of in-home water, according to a review published in Children (Basel). According to the authors of the review, H. pylori is one of the “most important leading infectious causes of cancer worldwide, as 8 in 10 gastric cancers in adults are attributable to this infection.”2

In the study, investigators included individuals who were aged 50 years or younger from the United Kingdom’s Clinical Practice Research Datalink GOLD, a primary care database of anonymous medical records. Individuals were recruited between January 1988 and December 2018, with follow up until December 2019, according to the study authors. At time of enrollment, all individuals were free of dementia.3

3 Key Takeaways

  1. A study suggests that individuals with clinically acquired H. pylori infection (CAHPI) face a 24% increased risk of Alzheimer's disease (AD) a decade after infection onset.
  2. The findings aim to provide insights into H. pylori infection's potential role in dementia, paving the way for prevention strategies, including individualized eradication programs.
  3. Understanding the potential link between H. pylori infection and AD risk may contribute to improved treatment measurement in clinical trials and risk monitoring for cognitive decline in aging populations.

There were 4,262,092 individuals included, with an average age of 60.4 years and 52.1% female, according to the study. Characteristics were similar among the 40,455 AD cases and 1,610,502 individuals with AD, which were used as controls.3 Compared to those who had no exposure to CAHPI, those who were exposed were associated with moderately increased risk of AD. The increase peaked at 7.3 to 10.8 after CAHPI onset, according to the study authors. Investigators also reported that there were no major effects when adjusting for demographics or socioeconomic status.3

When adjusting for 3- and 5-year lag periods, censoring follow-up upon non-AD dementia, using alternative CAHPI definitions, etc., did not change the results, according to the study authors.

“The application of a 10-year lag period led to a slight decrease in the OR and a lower number of exposed cases that resulted in loss in precision with wider CIs,” according to the investigators.3

An analysis with salmonellosis, used as a control exposure, showed no association with the risk of AD, according to the study authors. Furthermore, the results also demonstrated consistent outcomes with any type of dementia.3


  1. The stomach bug that may raise your risk of Alzheimer’s disease. News release. EurekAlert. December 22, 2023. Accessed January 2, 2024.
  2. Borka Balas R, Meliț LE, Mărginean CO. Worldwide Prevalence and Risk Factors of Helicobacter pylori Infection in Children. Children (Basel). 2022;9(9):1359. doi:10.3390/children9091359
  3. Douros A, Ante Z, Fallone CA, Azoulay L, et al. Clinically apparent Helicobacter pylori infection and the risk of incident Alzheimer's disease: A population-based nested case-control study. Alzheimers Dement. 2023. doi:10.1002/alz.13561
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