The Geography of Sudden Infant Death Syndrome in North Carolina

THE GEOGRAPHY OF SUDDEN INFANT DEATH SYNDROME IN NORTH CAROLINA Jack H. Rlok Sudden Infant Death Syndrome, which is the largest killer of infants in the United States between the ages of 28 days and one year, was defined at the 1969 Second International Conference on Causes of Sudden Death in Infants as: (Jj The sudden death of any infant or young child, which is unexpected by history, and in which a thorough post-mortem examination fails to demonstrate an adequate cause for death. Medically, this definition has several weaknesses. It very likely includes a number of disease entities which have yet to be discovered, and the definition is an exclusionary one which conveys misleading impressions about Sudden Infant Death Syndrome or SIDS. (2) With the mounting numbers of SIDS cases which have been studied, most researchers of SIDS are in agreement that, "SIDS is, with rather uncommon exceptions, a diagnosis that can be made with considerable certainty on the basis of positive findings." (3) For the medical geographer the exclusionary definition of SIDS creates problems and offers a challenge. The problems stem from the uncertainties on how best to approach the study of this disease, the etiology of which is still a mystery. The central concept of medical geography, which is generally agreed upon, holds that disease is an interaction between agent, host, and environment. (4) Adherence to this concept may assist in the selection of appropriate research methods when studying a disease with a known etiology. In the case of SIDS this concept is of little direct help in the formulation of a research design, and therein lies the challenge of the exclusionary definition of SIDS to medical geography. With the existing lack of knowledge about SIDS, medical geographers are in a position to make important contributions to the emerging epidemiological and, possibly, the etiological understanding of this particular disease. Dr. Blok is assistant professor of geography at East Carolina University, Greenville , NC 27834. 38Southeastern Geographer STUDIES OF SUDDEN INFANT DEATH SYNDROME IN THE UNITED STATES. Almost all studies of SIDS in the United States have been confined to a number of large metropolitan areas. In only a few instances have attempts been made to study the distribution of SIDS cases over an entire state. One such study, in California, made use of the death certificates filed there in 1968 to determine county incidence rates of post-neonatal sudden unexplained deaths. (5) The only state-wide study to date in which pathological correlation of SIDS cases was reasonably assured was completed for North Carolina in 1976. (6) Both of these studies contain choropleth maps depicting SIDS incidence rates per thousand live births by counties. COMMON EPIDEMIOLOGICAL OBSERVATIONS ABOUT SIDS IN METROPOLITAN AREAS. Virtually all SIDS cases have at least two factors in common: age and sleep. In almost all cases death comes during sleep and only rarely have cases been reported where infants expired suddenly while apparently being awake. It is also most commonly reported that the peak incidence occurs between the ages of two and four months. Other factors frequently present, but not constantly associated, are minor upper respiratory infections (usually viral) , prematurity at birth, and low socioeconomic status. (7) Of these associated factors, the implication of a relationship between SIDS and low socioeconomic status lends itself most readily to geographical analysis. Nearly all workers with SIDS have reported that more deaths occur in winter than in summer. (8) Clustering of cases within certain months or weeks has also been suspected, but this has not been demonstrated statistically. (9) Seasonal peaks in SIDS cases may also imply potential climatological relationships. The epidemiological observations made about SIDS pertain mainly to cases in urban areas, and they can be extended only inferentially to rural areas, or to smaller cities. Questions have been raised in medical literature as to whether the SIDS rates reported for large urban areas differ significantly from those of smaller cities. (JOj It has been observed that SIDS incidence rates within major metropolitan areas vary considerably, and that this variability likely reflects of the socioeconomic differences of the populations being compared. The question has also been raised whether the incidence of SIDS in upper or middle...