Ibuprofen and other non-steroidal anti-inflammatory (NSAID) drugs might be more dangerous than most people think, according to a new study that links these over-the-counter painkillers to heart problems.

Though drugs containing ibuprofen such as Advil are widely sold without a prescription in gas stations and grocery stores around the world — giving consumers the impression that they're relatively safe — researchers at Copenhagen University Hospital determined that these drugs raise the risk of cardiac arrest by about 31 percent on average.

The researchers are calling for stricter regulation of NSAIDs, such as requiring a prescription to obtain these products, in order to ensure that patients are better informed about the health risks. The risk is greatest for individuals suffering from heart conditions like cardiovascular disease, they found.

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"Allowing these drugs to be purchased without a prescription, and without any advice or restrictions, sends a message to the public that they must be safe," Gunnar Gislason, a professor of cardiology who co-authored the study, said in a press release. "The findings are a stark reminder that NSAIDs are not harmless."

Though past studies have arrived at similar conclusions about the cardiac risks of ibuprofen, this new research only looked at NSAID use among patients who were prescribed the drug. The ingredients are the same, but as one UK trade group representing over-the-counter drug makers told The Guardian, "[p]rescribed NSAIDs would normally contain a higher dosage than those medicines available over-the-counter and would typically be used for longer durations."

For the study, which was published in the European Heart Journal on Wednesday, researchers looked at about 29,000 patients in Denmark who experienced heart attacks from 2001 and 2010. About 3,300 of those patients had taken an NSAID in the 30 days before the cardiac event, and the study compared that finding to each patient's medical records from the preceding 30 days to evaluate the risk. Here's what they found, according to the press release:

"Use of any NSAID was associated with a 31 percent increased risk of cardiac arrest. Diclofenac and ibuprofen were associated with a 50 percent and 31 percent increased risk, respectively. Naproxen, celecoxib and rofecoxib were not associated with the occurrence of cardiac arrest, probably due to a low number of events."

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NSAIDs appear to raise the risk of cardiac arrest by causing platelets to build up, which can lead to blood clots. The study also indicated that these drugs make arteries constrict and increase blood pressure.

To avoid adverse cardiac effects of NSAID use, the researchers recommend taking no more than 1,200 milligrams of ibuprofen per day, and to limit use in general.