They may reduce the effectiveness of clopidogrel (Plavix), a drug that prevents blood clots.

In addition to those risks, two recent studies have raised troubling new questions about the long-term use of these drugs.

The first study, published in February, found that PPI use was tied to a higher risk for chronic kidney disease, while the use of a different kind of acid-blocking drug, called an H2 blocker, was not.

The second study, published in April, found a higher risk for dementia in people who use PPIs compared to those who don’t.

The studies linking PPIs to long-term health problems have been high-quality, but observational, experts say. At best, they can only show when two trends travel in the same direction. They can’t prove one thing causes another.

Scott Gabbard, MD, a gastroenterologist at the Cleveland Clinic in Ohio, says so many of his patients have become frightened of PPIs that he’s had to do his homework so he can fully explain the risks.

Take, for instance, the recent study that linked PPIs to chronic kidney disease. The study, which included more than 250,000 people, found that taking a PPI hiked a person’s risk of kidney disease by about 50%. But in absolute terms, the increased risk was still relatively small. Over 10 years, people who took a PPI had an almost 12% risk of developing chronic kidney disease, while people who weren’t taking the drugs had an 8.5% risk of getting kidney disease -- a difference of about 3%.

The same goes for the recent study that tied PPIs to dementia. Gabbard says the absolute risk increase seen in the study was small. People who took these meds had a 13% risk of getting dementia over the 7 years of the study, while people who didn’t take them had about an 8% -- a difference of about 5%.

Older studies have raised other health concerns. A 2015 study linked PPIs to a higher risk for heart attacks.

Also, there’s an ongoing debate about whether taking a PPI may increase a person’s risk for cancers of the esophagus and stomach.