Breast-fed babies arouse more readily from deep sleep, Monash researchers have found, in a discovery that could help reduce deaths due to Sudden Infant Death Syndrome (SIDS).
An ability to wake up from sleep is believed to be an important survival mechanism that may be impaired in victims of SIDS. Although education programs to encourage parents to put babies to sleep on their backs and protecting babies from exposure to passive smoke have been effective in reducing the number of SIDS cases worldwide, it remains the major cause of death in infants aged between one month and one year.
Dr Rosemary Horne and colleagues from the Department of Paediatrics and the Ritchie Centre for Baby Health Research at the Monash Institute of Reproduction and Development have investigated whether breast-fed infants wake more readily from sleep than formula-fed infants.
Their research has been published in the Archives of Disease in Childhood.
Babies have two basic sleep states - quiet sleep and active sleep. Active sleep is equivalent to REM (rapid eye movement) sleep in adults, which is a deep sleep and when dreaming occurs. Quiet sleep is similar to non-REM sleep.
"People have queried which sleep state is the most dangerous for babies," Dr Horne said. "In quiet sleep, babies have more control over their physiology - their breathing and heart rate are quite regular. But in active sleep their breathing and heart rate are irregular and often babies will stop breathing for short periods of time. It appears that SIDS babies may be unable to rouse themselves and start breathing again.
"We also believe that babies who die from SIDS die toward the morning, which is when they have more active sleep."
Dr Horne and her colleagues - Dr Peter Parslow, Ms Dorita Ferens, Ms Anne-Maree Watts and Associate Professor Michael Adamson - studied 43 healthy full-term infants who had been breast-fed or formula-fed and looked at how readily these infants woke from active sleep and quiet sleep.
The researchers attempted to wake the infants with a ticklish sensation - a gentle puff of air up the nose - when the babies were aged two to four weeks, two to three months and five to six months.
"We found that breast-fed infants were more easily aroused from active sleep at two to three months of age than formula-fed infants," Dr Horne said. "Two to four months is the age at which the risk of SIDS is greatest. Very few babies die under one month, and the number dramatically decreases after four to five months."
The researchers found no difference in the arousal responses of formula- and breast-fed babies during quiet sleep at any of the three ages studied.
"These study results support breast-feeding of infants during the critical risk period for SIDS, as reduced arousal, particularly in active sleep, could impair the ability of an infant to respond appropriately to a life-threatening situation," Dr Horne said.