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Sudden unexpected death in infants in the Oxford record linkage area. An analysis with respect to time and place.

Beckwith (1970) proposed the following definition of the syndrome of sudden unexpected death in infancy (SUD): 'The sudden death of any infant or young child, which is unexpected by history, and in which a thorough postmortem examination fails to demonstrate an adequate cause for death'. As other causes of infant mortality are gradually being reduced, the entity sudden unexpected infant death (cot death) is coming more and more into prominence. It is thought to account for as many as 30% of deaths to infants between 1 and 12 months of age (Froggatt, Lynas, and MacKenzie, 1971a). It is now well established that the incidence increases in the cold months of the year, in both the northern and southern hemispheres (Valdes-Dapena, 1967; Froggatt et al, 1971a; Steele, Kraus, and Lang worth, 1967). Theories abound as to the cause of this syndrome?from a deficiency of magnesium (Caddell, 1972) or vitamin D (Kraus, Steele, Thomp son, and de Grosbois, 1971) to parathyroid insuf ficiency (Geertinger, 1967), hypersensitivity to cow's milk (Gunther, 1972), viral infection (Ray, Beckwith, Hebestreit, and Bergham, 1970; Brandt, 1970), and myeloid leukaemia (Stewart, 1972). The present study is undertaken in an attempt to test certain of these hypotheses against the epidemi ology of the condition as observed over a five-year period in the Oxford Record Linkage Area. The study has been undertaken as a purely statistical exercise from the linked records in our files. At no time were the families of cases or controls contacted. Although, therefore, deficient in data on aspects concerning the social environment, state of maternal care, and morbidity of the child in the period before death, these aspects have already been investigated thoroughly (Vaughan, 1968; Richards and Mcintosh, 1972) and it is unlikely that further investigation would have brought anything new to light. The present study, on the other hand, has the advantage of large numbers, an unbiased recorder (the com puter-based file), and the advantage of linking with details of delivery, hospital admissions to mother, index case and sibs, and the ability to control for several variables at once from the population of all births in the area. This first report of the study will be concerned with defining the population of index cases and analysing the inci dence with respect to age at death, sex, date of death, and area of residence of the parents. It is intended that further papers will be concerned with the mother, the pregnancy and delivery, and a profile of the baby from birth to death.