Sydney:
Maternal smoking has replaced sleeping on stomach as the biggest risk factor for sudden infant death syndrome (SIDS), according to a new study.
The study showed that babies exposed to higher smoke levels had the lowest rate of cortical arousals, linked with increased wakefulness, muscle-tone, heart rate and breathing.
Senior study investigator Rosemary Horne, from the Ritchie Centre for Baby Health Research at Monash University in Melbourne, said decreased cortical arousals from sleep have been observed in victims of SIDS prior to death.
"Our study suggests that maternal smoking can impair the arousal pathways of seemingly normal infants (from sleep) which may explain their increased risk for SIDS," said Horne. SIDS is the third-leading cause of infant mortality in the US.
The study involved 12 healthy, full-term infants born to mothers who smoked an average of 15 cigarettes daily. Their arousal responses during daytime sleep were monitored and compared with that of 13 healthy infants who were born to non smoking mothers.
Daytime polysomnography (PSG, a multi-parameter test used in the study of sleep) was performed on each child on three occasions: at 2 to 4 weeks, 2 to 3 months and 5 to 6 months of age.
Arousals were induced without compromising the infants' natural sleep cycles by delivering an air-jet for five seconds at the infants' nostrils, said a Monash release.
According to the authors, 15 to 25 percent of pregnant women in western countries smoke throughout pregnancy.
The study was published in Wednesday's issue of 'Sleep'.