澳门金沙网上娱乐平台官网:Science: New research focuses debate on cot deaths

时间:2019-03-04 05:15:02166网络整理admin

By PHYLLIDA BROWN OVER the past few weeks, several teams of researchers have added to the complex debate over the sudden infant death syndrome, or cot deaths. SIDS is now the commonest classification of death in England and Wales for babies aged between four weeks and a year, but remains unexplained. The new research focuses attention on the sleeping baby’s position, its environmental stimulation, its control of temperature and its respiratory system. But the results have so far produced more hypotheses than conclusions about why many of these tragic deaths occur. Several previous studies had found a higher proportion of babies lying on their fronts among those that died than among controls (The Lancet, vol ii 1987, p 512). For the past two decades, many Western parents have placed babies on their fronts to sleep to prevent them from inhaling any regurgitated food which could choke them. Now, a team led by Natalie Lee, at the Prince of Wales Hospital in the Chinese University of Hong Kong, has found that 44 per cent of a group of babies that died of SIDS usually slept on their fronts, compared with only 7 per cent of the control group of babies (British Medical Journal, vol 298, p 721). However, there were only 16 babies that died and only 32 controls. In a separate study published in the same issue of the journal, a team of researchers in the Netherlands questioned the reasons for a threefold increase in that country’s incidence of SIDS since 1971. Guus de Jonge at the Free University Hospital in Amsterdam and his colleagues found that the incidence of SIDS in the group studied was almost five times as high in infants who usually slept on their fronts as among those who slept in other positions (p 722). The Foundation for the Study of Infant Deaths in London advocates placing a baby on its side to sleep unless it has a medical condition requiring it to lie on its front, such as certain specific respiratory problems. However, Erica De’Ath, the foundation’s chief executive, stresses the danger of oversimplified pronouncements about sleeping positions; she says that a baby will adopt a comfortable position of its own accord as it grows older. She also points out that the study from Hong Kong looked at a small, rather selective sample and does not represent the full social range, making it difficult to compare with studies in Britain. The incidence of SIDS in England and Wales varies between ethnic groups. Rasaratnam Balarajan and his colleagues at the Epidemiology and Public Health Research Unit at the University of Surrey in Guildford, and the Office of Population Censuses and Surveys in London, have made the first detailed comparison of the incidence of SIDS between ethnic groups in England and Wales (British Medical Journal, vol 298, p 716). In babies in Britain aged between four weeks and one year, the incidence of SIDS appears to be significantly lower among those whose mothers come from the Indian subcontinent and Africa than among those whose mothers were born in Britain or the Republic of Ireland. Among those whose mothers came from Asia, the rate was half or less than half that of the babies of indigenous mothers. Even infants of mothers born in Pakistan, who had a significantly higher mortality rate for all other causes, had a lower rate of SIDS than those whose mothers were born in Britain. Balarajan finds these results ‘paradoxical’, given that there is a higher overall rate of infant mortality in poorer social classes than in richer groups. SIDS, too is almost twice as common in the richest social group as in the poorest group. Mothers born in Pakistan and Bangladesh tend to be poorer, have more children and shorter intervals between pregnancies than indigenous mothers, the researchers point out. All these factors tend to increase the risk of infant death from various causes. But despite finding a high proportion of mothers coming from Asia in the poorest economic groups, they found that the incidence of SIDS was low in these groups. The team also found that fewer babies whose mothers came from Asia died of so-called respiratory distress syndrome in the first week after birth than babies of the same age whose mothers came from Britain. This separate syndrome, affecting largely premature infants, occurs where the lung has not developed properly. Balarajan says that he has a ‘hunch worth pursuing’ that the lower incidence of SIDS and respiratory distress syndrome, as well as other respiratory diseases, in babies of Asian origin might be related in some way. Balarajan is interested in the information gleaned from further ethnic comparisons. The principal conclusion of the study in Hong Kong is that SIDS there is extremely rare. Lee’s team found only 0.3 cot deaths per 1000 live births, compared with rates between 2 and 4 per 1000 in most Western countries and about 5 per 1000 in New Zealand’s South Island. As in all such comparisons, researchers are wary of the different definitions of sudden infant death from one culture to another. The team in Hong Kong speculates that their country’s overcrowded homes mean that an infant is never alone or without environmental stimuli such as noise, even when sleeping. This factor, combined with the tradition of lying the baby on its back, could protect it from sudden death, they suggest. Balarajan speculates that many Asian households, living in extended families, could also offer greater stimuli to the infant and have different patterns of infant care such as more breast-feeding, and different sleeping habits. Yet another alternative hypothesis comes from researchers at the University of Otago at Dunedin in New Zealand. South Island’s high incidence of SIDS, they believe, might be related to particular combinations of practices for infant care – a tendency to place babies on their fronts, wrap them up heavily with blankets and lie them on soft mattresses and sheepskins. They looked at previous research which found that a significant proportion of babies found unexpectedly dead were very hot, with rectal temperatures above 38 Degree C. The team at Dunedin constructed a theoretical model of heat balance, to examine the way in which a baby loses heat when wrapped with blankets. Their model showed that the face is an important area for cooling in such conditions, and they speculate that if the model is correct, lying on their fronts may contribute to overheating which could then combine with other factors that lead to death (The Lancet, vol i 1989, p 199). Tony Milner, professor of paediatric respiratory medicine at the University Hospital in Nottingham, says that researchers need to focus on the baby’s breathing. He is developing a device that will monitor babies’ throats with a fine fibre-optic wire attached to a TV monitor. Most researchers agree that the respiratory system, environmental factors and the baby’s position and temperature are the most important factors to consider. They also need to know how many of the infants diagnosed as dying of SIDS today would have had a different diagnosis in the past (The Lancet, vol i 1989, p 674). The view seems to be that we must expect to find several causes, not one,