LONDON (AP) — Stroke patients over 70 who get stents to keep their arteries open may be doubling their risk of having another stroke or dying compared to patients who get surgery instead, a new study says.

European researchers examined past studies from more than 3,400 stroke patients, including 1,725 who got stents and 1,708 who had surgery, and found that a patient's age makes a big difference in how effective stents are.

In patients older than 70, 12 percent of those who got a stent had a stroke or died within four months of the procedure, versus about 6 percent of the patients who only had surgery.

In those under 70, there was no difference between the groups — about 6 percent in each had a stroke or died within that time period.

The study was published Friday in the journal Lancet and was paid for by Britain's Stroke Association.

In February, an American study found stents were as safe as surgery for treating narrow neck arteries. It also found the stents were more dangerous in patients older than 70.

"When the (U.S.) study came out, people were interested to see stenting could match surgery but were still cautious about rushing out to use them," said Dr. Helmi Lutsep, a professor of neurology at Oregon Health & Science University and associate director of the Oregon Stroke Center who was not linked to the Lancet research. "This will hopefully lead to stenting finding its right place in the right patients."

Doctors think stents may be more dangerous in older people because their arteries are more easily damaged during the procedure to put the stents in place.

Martin Brown, a professor of neurology at University College London and the study's lead author, said the research confirmed that younger patients may have a choice between a stent or surgery.

Patients who get a stent have a tube inserted into their groin that is pushed up to the narrowed artery. A balloon is inflated to flatten the blockage and the stent holds the artery open. Patients are awake but sedated and recover within several days.

For the surgery, patients undergo general anesthesia. Their necks are cut open and the blockage is removed. They stay in the hospital for up to a week and can take several more to recover.

Tony Rudd, a stroke doctor at Guy's and St. Thomas' Trust at King's College London, said there wasn't a big price difference between the two procedures in Britain.

"Most (European) physicians have not adopted the wholesale use of stents," he said. "This study makes us very aware there are certain patients in whom they are too risky."