London: A combination of sensory stimuli -- by way of swaddling, sound and movement -- can effectively help parents to soothe their crying babies, according to a study.
Researchers, including those from the University of Amsterdam (UvA) in the Netherlands, discovered an immediate calming response, irrespective of whether the infant was soothed by its parent or a 'smart crib'.
A frequently crying infant can have a major impact on both the infant itself and its parents, according to the study published in the journal PLOS ONE.
Parents of excessively crying infants are often exhausted and experience symptoms of depression, researchers said.
Excessive crying is even associated with infant hospitalisation and shaken baby syndrome, they said.
There are, however, no proven effective prompt soothing methods for excessively crying infants under the age of six months.
Researchers from SEIN, the expertise centre for epilepsy and sleep medicine, and the UvA investigated whether the combination of swaddling (wrapping the baby in a swaddle sack), sound (shushing) and movement (swinging) induce a spontaneous calming response when parents soothe their baby or when a 'smart crib' soothes the baby.
They also examined whether the age of the baby influences the calming response.
Researchers looked at 69 babies aged up to six months. Each baby and one of its parents came to the UvA Family Lab.
They did a so-called counterbalanced experiment that consisted of two conditions: the parent and the smart crib.
Each of the two conditions involved three two-minute phases: baseline (to be able to determine the baseline value), laying on the back, and soothing.
"During the baseline the baby sat on the parent's lap. We then induced fussiness by putting the baby on the back, followed by parental soothing the parent shushed and rocked the swaddled baby," said researcher Eline Moller.
"We went through the same phases with the smart crib as a comforter. The smart crib also swings the baby and also makes a shushing sound," she said.
The researchers recorded the level of fussiness in the babies through observation; the baby's heart rate and heart rate variability were also measured to record physiological fussiness.
Fussiness and the baby's heart rate were lower in both soothing phases, irrespective of whether the parent or the crib did the soothing, than in the previous phase in which the baby was laying on its back.
This indicates that in both conditions the babies responded with a calming response to swaddling, movement, and sound, researchers said.
The baby's heart rate variability was higher during parental soothing than in the back phase, but during soothing by the smart crib the heart rate variability did not differ significantly from the back phase.
Younger babies responded with a stronger calming response than older babies when they were soothed by the parent.
This difference was not visible with the smart crib, researchers said.
"As for the baby's heart rate, we saw that the calming response was stronger during mechanical soothing (the smart crib) than during parental soothing.
"We saw the opposite when it comes to the observed fussiness: the calming response was stronger with parental soothing than with mechanical soothing," said Moller.