Gently stroking a baby before a medical procedure can help reduce pain processing in the brain, according to a new U.K. study published in the journal Current Biology.

The findings suggest that lightly caressing an infant at a certain speed — a little more than one inch per second — could provide effective pain relief before clinically necessary medical procedures.

“Parents intuitively stroke their babies at this optimal velocity,” said senior author Dr. Rebeccah Slater, professor of pediatric science at the University of Oxford, who worked alongside collaborators from Liverpool John Moores University.

“If we can better understand the neurobiological underpinnings of techniques like infant massage, we can improve the advice we give to parents on how to comfort their babies.”

For the study, the team measured newborns’ pain responses to medically necessary blood tests by observing their behavior and detecting their brain activity using electroencephalography (EEG), a technique that measures tiny bursts of electrical activity from the surface of the brain. Half of the babies had their skin gently stroked with a soft brush right before the blood test.

Previous research by Slater showed that EEG activity increases in the infant brain immediately after a blood test. This pattern of pain-related brain activity can be reduced by interventions, such as the application of a local anesthetic prior to the procedure.

In her most recent experiment, she found that infants who received light caresses exhibited lower pain-related EEG activity, but the babies still reflexed their limbs away from the stimulus.

“We hypothesized that stroking would reduce pain-related brain activity, so we were pleased to see it. But we didn’t see a reduction in how they reflex their limbs away from the heel lance,” says Slater. “That could mean our intervention is perhaps causing a dissociation between limb movement and brain activity.”

The optimal pain-reducing stroking speed of an inch per second is the same frequency that activates a class of sensory neurons in the skin called C-tactile afferents, and has been shown to reduce pain in adults. Up until now, it was unclear whether this sensory response occurred in newborns or developed over time.

“There was evidence to suggest that C-tactile afferents can be activated in babies and that slow, gentle touch can evoke changes in brain activity in infants,” Slater said.

The pain-easing power of stroking appears to be clinically useful, said Slater. It could explain anecdotal evidence of the soothing power of touch-based interventions such as infant massage and kangaroo care, the practice of holding premature babies against the skin to encourage parent-infant bonding and possibly reduce pain.

The research team plans to repeat their experiment with premature babies, whose sensory pathways are still developing.

Source: Cell Press