     Vol 118 No 1227 ISSN 1175 8716 NZMJ 16 December 2005, Vol 118 No 1227 Page 1 of 11 URL: http://www.nzma.org.nz/journal/118-1227/1788/ © NZMA Hong Kong case-control study of sudden unexpected infant death Tony Nelson, Ka-Fai To, Yuk-Ying Wong, Jim Dickinson, Kai-chow Choi, Ly-Mee Yu, Yvonne Ou, Chun-Bong Chow, Eric Wong, Nelson Tang, Magnus Hjelm, Lawrence Chen Abstract Aim To document causes of all unexpected child deaths under 2 years of age during a 4-year period (1999–2003), and to identify factors associated with sudden infant death syndrome (SIDS) in Hong Kong. Methods The case-control component of the study compared information from SIDS deaths (n=16) with healthy controls (n=223) identified randomly from all births in Hong Kong. Coroner records of all deaths under 2 years of age were later reviewed. Results SIDS risk factors included prone sleep position, smoking by mother, bedsharing with someone other than the parents, and baby found with head covered. Eighteen deaths were officially classified as SIDS but, on review of the coroner records, there were 33 potential SIDS deaths (many labelled as unascertained/unknown). Conclusion Hong Kong SIDS incidence has fallen from 0.3/1000 (95% CI: 0.18–0.46 in 1987) to 0.16/1000 (95% CI: 0.11–0.22 in 1999–2002). Despite the small number of cases, key SIDS risk factors are shown to be important in this population. Hong Kong needs to take steps to standardise the investigation and management of these deaths and to establish a child mortality review mechanism to provide feedback to the public, to the health authorities, and to health professionals. Sudden infant death syndrome (SIDS) was originally defined as the sudden death of an infant or young child, which is unexpected by history, and in which a thorough postmortem examination fails to demonstrate an adequate cause of death. 1 Other definitions have been suggested, 2 and recently a new definitional and diagnostic approach has been proposed. 3 At a time when New Zealand was reporting very high rates of SIDS (3.6-7.4/1000 live births in 1986), Hong Kong had very low rates (0.3/1000 lives births in 1987). 4,5 In the United States and Europe during the same period, reported rates were in the region of 1 to 2/1000 live births. 6 Subsequent research studies in a range of countries have shown that certain childcare practices are associated with SIDS. Placing the baby to sleep on the front (prone) has been identified to be the most important risk factor; but other factors include smoking by the mother or father, the baby sleeping in the same bed as someone else (bedsharing), baby sleeping in a room separate from the parents, and baby not using a pacifier (dummy). A striking reduction of SIDS incidence of more than 50% has been observed in many countries after parents were advised not to place their babies on their front to sleep. 7