TUESDAY, Dec. 21 (HealthDay News) -- A new study finds that more babies die of sudden infant death syndrome (SIDS) in the United States on New Year's Day than any other day of the year.

It's not clear why, but researchers suspect it has something to do with parents who drink heavily the night before and put their children in jeopardy.

"Alcohol-influenced adults are less able to protect children in their care. We're saying the same thing is happening with SIDS: They're also less likely to protect the baby from it," said study author David Phillips, a sociologist. "It seems as if alcohol is a risk factor. We just need to find out what makes it a risk factor."

SIDS kills an estimated 2,500 babies in the United States each year. Some researchers think genetic problems contribute to most cases, with the risk boosted when babies sleep on their stomachs.

Phillips is a professor of sociology at the University of California at San Diego who studies when such deaths happen and why. He said he became curious how the choices made by parents may affect SIDS and launched the new study, which appears in the current issue of the journal Addiction.

Researchers analyzed a database of 129,090 deaths from SIDS from 1973-2006 and 295,151 other infant deaths during that time period. They found that the highest number of deaths from SIDS occur on New Year's Day: They spike by almost a third above the number of deaths that would be expected on a winter day.

The study doesn't prove that anything is the cause of the SIDS deaths. (The number of other kinds of infant deaths didn't spike significantly on New Year's Day.) However, the researchers point out that there's plenty of drinking on New Year's Eve. They point to research that says the number of people involved in alcohol-related car crashes skyrockets on New Year's Eve, well beyond any other day of the year.

Why might boozing on New Year's Eve night threaten babies on New Year's Day? Phillips thinks that drunk parents are doing something -- or not doing something -- that puts babies at higher risk. But he acknowledges that the study doesn't prove that.

"I would say there's enough evidence here to warrant further investigation," he said, "but not enough to make every parent of every SIDS baby a suspect."

One SIDS specialist said parents who have too much to drink may miss the signs of a baby in distress while they're asleep. "If you can't awaken your own self, how will you be sensitive if a baby is vulnerable?" asked Dr. Debra E. Weese-Mayer, professor of pediatrics at Northwestern University Feinberg School of Medicine.

Ultimately, she said, caregivers of babies shouldn't drink at all, even if they avoid becoming drunk. "Parents and caregivers need to grow up. If you're going to take care of a child, you have to be responsible."

More information

For more about SIDS, try the U.S. National Library of Medicine.