People taking common heartburn and indigestion medicines may face a heightened risk of premature death, according to new observational research published Monday in the "British Medical Journal Open."

» RELATED: Common painkillers increase risk of heart attack by one-third, new study finds

A team of scientists from the Washington University School of Medicine in St. Louis, Missouri, found that the use of proton pump inhibitors (PPIs) — drugs commonly taken to treat both heartburn and stomach acid — led to 25 percent higher risk of early death by any cause when compared to those using H2 blockers, common acid reducers.

To come up with the findings, the team examined medical records of 3.5 million middle-aged Americans in the U.S. Department of Veterans Affairs system and compared those taking PPIs and those taking H2 blockers to treat heartburn.

» RELATED: Differences between PPIs and H2 blockers for heartburn

Researchers did not examine over-the-counter PPIs or particular brands of prescription-strength drugs. Instead, the team focused on prescription PPIs typically used at higher doses and for longer durations, CNN reported.

According to senior author Ziyad Al-Aly, for every 500 patients taking PPIs for one year, there would be one additional death that wouldn’t have occurred if the patient wasn’t using PPIs.

And with millions of people using PPIs on a daily basis to treat heartburn and stomach acid, thousands of additional deaths could result.

» RELATED: Popular heartburn medications may increase dementia risk, study says

Al-Aly and his team also found that the longer a patient  used PPIs, the higher their risk of premature death.

Though the precise biological reason for a possible link between PPIs and risk of premature death is unclear, the gene-changing effect of the drugs may contribute to the potential problem.

Because the research is based on observational study, the team noted the findings are “far from conclusive,” meaning they do not prove cause and effect.

» RELATED: How dangerous are energy drinks, really? Study finds link to serious heart problems

But the findings "may be used to encourage and promote pharmacovigilance [monitoring the side-effects of licensed drugs]," the authors wrote, urging patients to be judicious in their use of PPIs and limit the duration of use unless there is a clear medical benefit that outweighs any potential risk.

It's not the first time PPIs have been linked to some dangerous health trends. Previous research has also shown links between the drugs and dementia, cardiovascular disease, hip fractures and more.

Read the full study.