New study links smoking to SIDs
Australian researchers have discovered the first evidence that exposure to cigarette smoke induces abnormalities in babies' brains, putting them at increased risk of sudden infant death syndrome.
By analysing the brain tissue of babies who had undergone an autopsy at Sydney's Glebe morgue, researchers from the University of Sydney found exposure to any second-hand smoke could precipitate these brain cell changes, and not just exposure in utero by maternal smoking.
The findings provide doctors and health workers with tangible evidence to persuade mothers and their partners not to smoke during pregnancy and to keep homes and cars smoke-free during the early months of life.
More than 1 in 10 women still smoked at some time during pregnancy, the latest data available in the NSW Mothers and Babies report 2006 said.
Rita Machaalani, a scientist at the university's Bosch Institute, said passive smoking had long been identified as a risk factor for SIDS, but the biological mechanisms that lead to death was unknown until now.
A death of an infant less than 12 months old that remains unexplained after thorough investigation is generally diagnosed as SIDS. Although deaths have halved since public health education programs began in the early 1990s, it remains the most common cause of death for this age group in developed countries, affecting an average 88 babies a year in Australia.
Dr Machaalani and her colleague Karen Waters showed there was an increase in cell death in a region of the brain that plays a major role in the control of breathing and heart function in babies who died of SIDS, compared to those who died of other causes. The post-mortems of 67 SIDS infants and 25 infants who died suddenly with another diagnosis between 1997 and 2002 were correlated with risk factors associated with SIDS, such as tummy sleeping, sharing a bed with adults and exposure to smoking, obtained during police interviews with the babies' parents and hospital records.
Of the 67 SIDS infants, 81 per cent had been exposed to cigarette smoke, compared to 58 per cent of non-SIDS infants, and 32 per cent were in bed with a parent when they died.
"No one in the world has access to such a large dataset of brain tissue or the ability to correlate the tissue with the autopsy results and a record of the risk factors and this is what makes our data really important," Dr Machaalani said.
The research, published in the journals Brain and Acta Neuropathologica, found the increase in cell death (apoptosis) was higher not only in SIDS victims, but in all infants who had a history of tobacco smoke exposure, in utero and the postnatal period.
"This study provides further evidence of increased apoptosis in the brainstem of SIDS infants but shows for the first time these changes are also affected by age and gender, and by clinical risk factors such as sleep position and cigarette smoke exposure," the authors concluded.
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