BOSTON (CNN) -- A heartbeat abnormality might be a risk factor for sudden infant death syndrome, according to the results of the largest SIDS study conducted.

Italian researchers, who studied 34,000 babies over a 19 years, found that an unusual heart rhythm, called a long QT interval, appears to be a contributing cause to the syndrome, in which newborns die for no discernible reason. The results are reported in the latest issue of the New England Journal of Medicine.

Long QT intervals can be easily detected by an electrocardiogram, or EKG. The study found that infants with the defect were 41 times more likely than usual to die of SIDS.

However, researchers said that while the results of the study are important, they are not enough to support any sweeping recommendation that all newborns be screen with an EKG, which many hospitals are not equipped to do.

Also, the risks of treatment could outweigh the benefits. In adults, a long QT interval abnormality is treated either with surgery or with drugs called beta blockers.

"I don't think we would be prepared to put a lot of small newborns on beta blockers, which have very bad side effects," said Dr. Julien Hoffman of the University of California at San Francisco.

Researchers also say their research, combined with results of earlier studies that found no link between the long QT interval defect and SIDS, lead them to the conclusion that that only 30 to 35 percent of SIDS deaths might be attributable to the problem.

That would still leave the bulk of SIDS deaths unexplained. And researchers also found that many babies with the long QT interval defect did not die of SIDS.

"Currently, the available information suggests that it's most likely to be a marker, a risk factor -- something that, if present and another trigger is present, will result in sudden death," Hoffman said.

About one in every 1,000 babies dies from SIDS. The rate dropped about 30 percent during the 1990s after doctors began warning parents to put babies to sleep on their backs, rather than their stomachs.

Medical Correspondent Rhonda Rowland and Reuters contributed to this report.