The National Association of Medical Examiners (NAME) in the United States asked me recently to present the history of SIDS.Reference Wright^[1] The context for this was an attempt to strike the term ‘SIDS’ from the medical lexicon, as proposed in the June 2017 theme issue of their journal Academic Forensic Pathology and replace this with ‘undetermined’. The articleReference Wright^[1] did not take sides on this thorny issue but was designed to provide historical context and help guide discussions within NAME. Since it was directed towards an American audience, it naturally had a somewhat American focus. My historical article caught the attention of the editors of this book, and they have asked me to write a brief historical entry highlighting important global contributions. While recognising that SIDS is not a single entity and that the use of this name, which dates back to only 1969, to classify deaths is controversial and may change in some jurisdictions, the term SIDS is used for simplicity’s sake, even though the three ‘SIDS investigators’ I will discuss did much or all of their important work before 1969.

Prior to the 1940s and 1950s, SIDS was generally thought to be due to overlying, infanticide, thymic asthma, status thymicolymphaticus, smothering by bedclothes, and accidental suffocationReference Wright^[1] which will not be covered here. Fundamental work published in the 1940s suggested that SIDS is a natural entity with typical pathological and epidemiological findings. The first of these types of studies included the publications of New York City forensic pathologist Jacob Werne in 1942, Birmingham UK pathologist W. H. Davidson in 1945, and Werne, and his wife Irene Garrow from 1947 to 1953; these papers all suggested that many of these sudden, unexpected infant deaths had natural causes and that performing autopsies demonstrated explainable causes of death in some instances and provided histopathological findings demonstrating vague, mild respiratory disease processes in most of the rest.Reference Wright^[1] These observations paved the way for the better understanding of SIDS that took place in the latter half of the twentieth century and changed the way these deaths were classified.Reference Wright^[1]

The next wave of investigators confirmed these preliminary findings and took epidemiological analyses much further, helping establish the entity that would be named SIDS by J. Bruce Beckwith in 1969.Reference Wright^[1] These included Melbourne forensic pathologist Keith Macrae Bowden (1908–1999), British Medical Journal editor Douglas Swinscow (1917–1992), and Sheffield paediatric pathologist John Lewis Emery (1915–2000). By virtue of the fact that they were working on opposite sides of the world, the convergence of their findings, combined with those of American investigators,Reference Wright^[1] were even more compelling.

Bowden published three important papers in the Medical Journal of Australia from January 1950 to November 1952.Reference Bowden^[2–Reference Bowden^4] He noted that about thirty babies per year were found dead in their cots in the Melbourne area. The first paper addressed the question ‘do babies accidentally suffocate in the bedclothes or face downwards on the bedding?’ It provides his intriguing analyses into babies’ spontaneous choices of sleep position at 2–7 months vs. 7–18 months of age and it comes very close to outlining the full ‘triple-risk model’Reference Wright^[1] currently used to explain SIDS. Bowden reported his autopsy series and concluded that if complete autopsies were performed, pathological findings are usually present. He notes that: ‘although in every case the question why sudden death occurred, and although the exact mechanism of death is obscure in some cases, in practically every case natural disease was present’.Reference Bowden^[2] In one of his cases, the cause of death was determined to be an inherited metabolic disease, predicting a fertile area of research that would begin several decades later.Reference Wright^[1] In his second paper, he added bacterial cultures and in some instances influenza virus cultures into his analyses and concluded that in twenty of forty-three cases, ‘histological evidence of respiratory tract infection can be found, but in which the aetiological agent was not isolated’.Reference Bowden and French^[3] He also observed that parents initially reported the infant to be ‘quite well when last seen’ before the death but, that when questioned later, ‘a carefully taken history revealed evidence of several days or weeks of minor illness’ in over two-thirds of cases.Reference Bowden and French^[3] Bowden’s final study examined overlaying as a possible cause of death in 179 consecutive infants brought to the Melbourne City Morgue after dying suddenly and unexpectedly. In only 11 instances, was one or both parents actually sleeping with the infant and in 10 of these instances a complete autopsy established a natural cause of death. Bowden concludes that in all of Melbourne over the past four years, ‘there has been one possible case of overlying’.Reference Bowden^[4] Bowden cited a forensic textbook claiming that accidental overlaying ‘causes quite an appreciable annual loss of life’ and that it is ‘the most common form of accidental smothering’, both of which he showed to be incorrect. All of Bowden’s papers support his major premise: ‘the more thorough the autopsy, the less the likelihood of a diagnosis of ‘accidental suffocation’’.Reference Bowden and French^[3]

Swinscow wrote only one paper on SIDS, but it was influential.Reference Swinscow^[5] ‘So-called accidental mechanical suffocation of infants’ was published in the British Medical Journal on October 1951; it called attention to the works of Davison, Werne and Garrow, and Bowden suggesting that many of these deaths had a natural cause. He then provided a detailed explanation of sex-ratio statistics and how they can be used to categorise deaths. Swinscow noted that: ‘The two main factors concerned here are the sex distribution of the population exposed to risk and the differing susceptibility, characteristic of each sex, to death from a particular cause. When comparing the sex ratios of death from two or more causes in the same population, we find that the main effective reason for the difference between them is the fact that the deaths are caused by different agents’.Reference Swinscow^[5] He then used England–Wales death statistics recorded by the Registrar-General for the years 1921–30, 1931–9, and 1940–9 to reveal that sex-ratio analyses showed a preponderance of male infants dying in cots and cradles when compared to infant deaths known to be accidental mechanical suffocation (eg., aspiration of food). He concluded ‘many of the cot deaths are caused differently from (known accidental mechanical suffocation) deaths … Yet all are alleged to be due to the same cause – accidental mechanical suffocation.’Reference Swinscow^[5] He further stresses ‘the effect that such a diagnosis may have on the parents … No infant’s death should be attributed to accidental mechanical suffocation unless there is clear positive evidence of it.’Reference Swinscow^[5]

John Emery’s contributions to the understanding of SIDS began in 1956 and he published at least another seventy-five papers on the topic after that. In fact, studying SIDS became a lifelong passion. One of his own children died in infancy, which gave him compassionate insights allowing him to deal with grieving families. According to A. H. Cameron:

Emery’s first SIDS paper began by citing Swinscow’s mortality statistics; next, he noted that Davidson ‘thought that most of these deaths were due to natural causes, and that with skilled necropsy the cause of death would be found’ but concluded, ‘unfortunately this is not wholly true’.Reference Emery and Crowley^[7] He noted that others have found only non-specific chronic inflammation in lungs. He then presented his own Sheffield data showing the added value of better history-taking. He notes that ‘in only five of 50 infants studied was the complete correct history available at the time of necropsy’ and ‘in 33 the history … available to the pathologist was not only inadequate but misleading’ (i.e., ‘wrong enough to affect the diagnosis’)Reference Emery and Crowley^[7] Emery also suggested that the autopsies be performed by a paediatric pathologist at the local children’s hospital.

Emery published papers on the epidemiology of SIDS for forty years.Reference Emery^[8–Reference Emery^11] As a pathologist, he also published detailed papers on subtle pathologic findings suggestive of chronic hypoxia (fat-laden cells in the cerebro-spinal fluid (CSF), retention of periadrenal brown fat cells, histopathological changes in the trachea) seen in SIDS starting in the mid-1970sReference Gadsdon and Emery^[12–Reference Wailoo and Emery^14] as well as papers showing that some pathologic changes reported by others are not specific to SIDS.Reference Cullity and Emery^[15]

Emery performed retrospective case-control studies on SIDS and control infants examining obstetric and perinatal histories in order to identify prospective ‘criteria for detecting children at increased risk of dying unexpectedly’.Reference Protestos, Carpenter, McWeeny and Emery^[16] He and his team then used this to develop a scoring system to identify infants at risk.Reference Carpenter, Gardner, McWeeny and Emery^[17] He established a programme of Sheffield ‘health visitors’, and Emery and colleagues reported that infants who were visited and weighed frequently and received safe-sleeping advice had fewer deaths than predicted.Reference Carpenter and Emery^[18] Within the identified high-risk group, they found symptoms that further predisposed to death.Reference Carpenter, Gardner, Pursall, McWeeny and Emery^[19] This work resulted in an interventional study which showed excellent results after seven years,Reference Carpenter, Gardner, Jepson, Taylor, Salvin and Sunderland^[20] as well as the Care of Next Infant (CONI) programme funded by the Foundation for the Study of Infant Deaths (now The Lullaby Trust) to provide support to families with new babies after having experienced a cot death.Reference Emery and Waite^[21] In the 1980s, Emery published controversial estimates that about 10% of ‘SIDS’ cases were actually filicide;Reference Taylor and Emery^[22] while it was important to acknowledge that some cases signed out as SIDS are really filicide and that forensic science cannot always identify these cases, current data suggests that his estimate was too high.Reference Milroy and Kepron^[23] However, Emery did publish data proposing a much higher incidence in families in which two or more SIDS deaths have occurred,Reference Emery^[24] a finding supported a decade later by the high-profile multiple infanticide convictions of Wanda Hoyt in New York and Marie Noe in Philadelphia,Reference Wright^[1] as well as chilling publications from Sir Roy Meadows and David Southall showing parents deliberately harming their infants.Reference Wright^[1, Reference Milroy and Kepron^23] Emery’s contributions to SIDS were many.

Keith Macrae Bowden, Douglas Swinscow, and John Lewis Emery made important pathological and/or epidemiological contributions to the establishment of SIDS as a diagnostic entity and helped advance its understanding. It is imperative that these be remembered, and their work has not been highlighted in a previous historical paper. For a more comprehensive history of SIDS and to see how the work of these three men fit into the overall picture, the readers are invited to read reference 1 below.