New research suggests that users of several popular heartburn drugs may be at increased risk for developing dementia.

Older adults who use proton pumped inhibitors (PPIs) such as Nexium from Pfizer (NYSE:PFE), Prilosev from AstraZeneca (NYSE:AZN) and Prevacid from Novartis (NYSE:NVS) may be at increased risk for dementia, according to a new observational study published in JAMA Neurology.

These over-the-counter medications reduce the amount of acid produced by the stomach, and help to remedy a variety of gastrointestinal ailments from GERD to esophagitis to peptic ulcer disease.

Researchers evaluated nearly 74,000 adults aged 75 and older without dementia in 2004, using claims from a large German health insurer’s pharmaceutical database. However, by 2011, close to 40% of the initial cohort were diagnosed with dementia.

The authors believe that PPIs may cross the blood-brain barrier, leading to increased production and degradation of amyloid protein (as noted in mouse models), and subsequently bind to tau protein.

PFE stock is up 1.5% Tuesday. AZN stock is up 2.19% and NVS stock is up 0.81%.

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