A Proton Pump Inhibitor (PPI) such as brand-name medications Prilosec, Nexium, Prevacid and others, reduces acid production by blocking the enzyme in the wall of the stomach that produces acid that can cause ulcers in the stomach, esophagus and duodenum.
The study was conducted by researchers at the Washington University School of Medicine in St. Louis and published in June 2017 in the BMJ Journal.
Scientists conducting the study gathered data from the US Department of Veterans Affairs databases on 275,933 people who were prescribed a PPI and 73,355 who had been prescribed an H2 blocker, another class of medication used to treat conditions that cause excess stomach acid, between October 2006 and September 2008.
The study, which tracked deaths up to five years, found a 25 percent increased risk of death in the patients who took a PPI compared with the people who took H2 blockers, roughly one extra death for every 500 people taking PPIs for a year, according to CBS News.
"The results were very clear. We were startled by this," study author Dr. Ziyad Al-Aly told CBS News. "However we sliced the data, analyzed it, there was always a consistent relationship between PPI use and risk of death."
Earlier published studies have linked the use of PPI medications, which are sold over-the-counter or by prescription, with a risk of adverse reactions.
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JAMA Internal Medicine published a February 2016 study that found that the use of PPIs was associated with a higher risk of chronic kidney disease. Another study published in April 2016 in the Journal of the America Society of Nephrology found that patients who took proton pump inhibitors for more than 30 days had an increased risk of kidney failure or chronic kidney disease.
The St. Louis study noted the need for limited use of PPIs in some instances.
"The results suggest excess risk of death among PPI users. Risk is also increased among those without gastrointestinal conditions and with prolonged duration of use. Limiting PPI use and duration to instances where it is medically indicated may be warranted," according to the study.