Heart attack patients who arrive at the hospital during the night or weekends are more likely to die, a new study published by the British Medical Journal found.

The report looked at 48 studies carried out in the United States, Canada and Europe; in all, nearly 1.9 million patients were included.

Based on the information, the researchers concluded that patients who arrive during off-hours face a 5 percent increase in mortality. This amounts to about 6,000 extra deaths each year in the United States alone, the researchers said.

For those with a STEMI heart attack, or ST elevation myocardial infarction, the study revealed a delay of nearly 15 minutes from the time the patient entered the door to the moment his or her coronary artery was inflated, also known as "door to balloon time."

Such a delay "could increase mortality by as much as 10-15 percent, assuming linearity between door to balloon time and mortality," the authors said.

Based on their results, the doctors at the University of Toronto wrote in an accompanying editorial that patients who arrive during off-hours "experience delays in urgent care and worse outcomes, and the gap seems to be increasing over time."

Future studies, they said, "should try to identify specific deficits in the care pathway during off-hours, allowing differences in outcomes to be linked to differences in processes."

According to the Centers for Disease Control and Protection, each year an estimated 715,000 Americans have a heart attack, of which 190,000 have already experienced one.

A 2005 survey revealed that while 92 percent of respondents recognized chest pain as a symptom of a heart attack, only 27 percent knew all major symptoms and to call 911 when someone was experiencing an attack.

The list of symptoms include chest pain or discomfort; upper body pain or discomfort in the arms, back, neck, jaw, or upper stomach; shortness of breath; and nausea, lightheadedness, or cold sweats.