Doctors at the Tel Aviv Sourasky Medical Center measured the energy expenditure of 20 infants born pre-term while listening to Mozart in their incubator. They compared that figure with the amount of energy they expended without the music. But the scientists did not test a control group to measure the energy used by babies who didn't listen to Mozart at all.
Among the babies in the study, the findings showed Mozart lowered the quantity of energy they used, meaning the babies may be able to increase their weight faster.
"While listening to this specific music, a baby can have a lower energy expenditure and hopefully he will gain weight faster than without music," said Dr. Ronit Lubetzky, one of the main researchers in the study, which was published in the current issue of the medical journal Pediatrics.
The researchers used as a starting point a controversial 1993 study that showed college students improved their IQs by listening to Mozart's sonatas for 10 minutes. Those findings sparked a craze that saw droves of parents buy Mozart CDs in a bid to boost their children's brain power.
Later studies challenged what became known as "the Mozart effect," saying classical music can't increase basic intelligence among children or adults.
The purported positive effects of Mozart's music is what drew the Israeli researchers to the topic. In their article, they note that the repetition of the melody in Mozart's compositions, which resonates with a particular part of the brain, is less frequent among other classical composers and may account for the potential benefits stemming from his music.
Each of the 20 babies was played Mozart for 30 minutes, and the amount of energy they spent was measured simultaneously. The next day, the energy expenditure of the same 20 babies was observed, but without the music.
With Mozart, the energy use was reduced by at least 10 percent for each baby. Data from two of the infants were not counted because of unrelated variations that could have skewed the results.
The study did not measure the infants' weight gain and only speculated that its findings could translate into a quicker weight increase.
Lubetzky said the reasons the babies used less energy listening to Mozart aren't entirely clear, but it appeared to have relaxed them.
"They might be more calm while listening to music, or they might have fewer stress hormones. All those things mean they have a lower heart and respiratory rate," she said, meaning they spend less energy.
Prior research studying the effect of music on premature babies has been conducted using other sounds, including live music and harps.
But this study is unique because it appears to be the first to have quantified the amount of energy spent while listening to the music, one neonatologist said.
Dr. Arthur Eidelman, a retired former head of pediatrics at Jerusalem's Shaare Zedek hospital who did not participate in the research, praised the new study but did not credit Mozart for the positive results.
"What's unique about Mozart is it's rhythmical, the range of decibel level is minimal," Eidelman said. "One could almost make the case that appropriate rap music may do the same thing if you have it within the right range of volume."
Lubetzky and the other researchers plan to conduct similar studies in the coming months that will test the effects of other music genres -- anything from ethnic tunes to Israeli pop -- on premature babies.