Epidemiology of Cot Deaths: The Northern Ireland Study

Abstract

Many family doctors have had the experience of being called urgently one morning to an infant dead in its cot. The child had been well when put to bed the previous night. Close enquiry might show that the child had had snuffles, or been off its food, or cried more than usual during the night but not to a degree to worry the parents. I n fact the parents do not believe that the child had any serious illness and they assume that it must have died from some unnatural cause. And what better than suffocation? At one time this was also the conclusion of the pathologist and the coroner. In recent times, however, the view has changed. I t is now generally agreed that these children die from a natural process but no one knows what it is. There are numerous theories (Froggatt et al., 1968) but none yet has been proved to be the right one. During 1965-7, when we carried out a study into the 70 or 80 cot deaths which occur each year in Northern Ireland, we were aware of the different theories but decided to settle the epidemiology of the condition before carrying out investigations into any one of them. Northern Ireland offered certain advantages for this; the country has a manageable size, 5,250 square miles, and a reasonably static population of 1.47 million fairly evenly divided into urban and rural communities. The coroner's law is such that all cot death infants should be reported; the coroners who are in the government service, investigate the deaths in a similar manner and always request an autopsy. The autopsies are carried out by pathologists working in the same medicolegal department and using the same technique, and the police who make the preliminary enquiries belong to a single force. I t was therefore easy to standardize the coroner's investigation. All that was required was to institute a social survey of the families of cot deaths and suitable controls. A doctor was employed, part-time, to visit each cot death family 2-3 weeks after the death so that a questionnaire could be completed concerning the family, the social background and the circumstances of the death. For each cot death a control family was interviewed; this was the family of the child of the same sex born in the same administrative area whose birth was registered next before, or next after, the cot death.