The findings are surprising because of a widespread belief that clot-busting drugs help older patients just as they clearly do younger ones.

It found that the benefits of clot-busting drugs varied markedly with age.

The Harvard study also showed an increased risk of death among heart attack patients older than 75 who received clot-busting drugs.

Of 289 patients older than 75 who received the clot-busting drugs, 58, or 20.1 percent, died.

Hours may pass before symptoms are recognized, reducing the chance doctors can use clot-busting drugs.

There are clot-busting drugs that can curb brain damage, but they have to be used within three hours of the initial stroke symptoms.

Those who get clot-busting drugs soon enough may recover completely.

Ideally, the panel said, clot-busting drugs should be given within one hour of the onset of symptoms from a heart attack.

If the person gets emergency care within the first several hours of stroke onset, the person may receive clot-busting drugs.

He was one of the first to popularize the use of clot-busting drugs for vascular disease.