Sudden-infant-death syndrome

Sudden infant death syndrome in Sweden in 1973-1977 and 1979

The aim of the investigation has been to describe Sudden Infant Death Syndrome, SIDS, in Sweden, its background, true incidence and epidemiological characteristics, and finally to offer possibilities of prophylaxis. The method used has entailed a retrospective survey of all 1,873 post-perinatal (1-51 weeks) deaths from six birth cohorts in 1973-1977 and 1979. Through comprehensive documentation, 334 deaths have been isolated as SIDS. The result was an incidence of 0.54/1000 live births. Internationally, this incidence is low, but the study could establish that SIDS increased during 1973-1977 and 1979 in Sweden. The epidemiological characteristics shown by the study agree to an extent with American and British investigations, but reported Swedish incidence is lower. An assessment of the total post-perinatal mortality has also been made to demonstrate that there is no communication between SIDS with a uniform diagnosis and other causes of death. Analysis has been binary: in relation to factors in society, and on an individual basis. Geographical or social bases did not affect incidence of SIDS in Sweden, which is remarkable when comparing these findings with other reports on the subject. In regards to individuals, the analysis has been based upon the place where the infant died. Deaths in the infant's own bed showed a clear rise on Saturdays, but the incidence here remained constant over the period studied. Deaths in bed with one/two adults showed epidemiological findings which indicated disadvantageous family and social factors in many cases; this group increased from year to year. Deaths outdoors were common in winter; a certain increase towards the end of the week as well as from year to year was indicated. No social strain was shown. Deaths during car rides clearly increased from year to year, but showed no particular socio-familial profile nor weekday variation. Findings analyzing location of death have indicated that the different places have their own epidemiological characteristics distribution. Analyses of this sort are scarce. There were no certain indications of SIDS occurring more often in socially disadvantageous circumstances: 4/5 of the SIDS families had no social strain. The study has also included medico-historical notes, e.g. 'over-laying' and a description of epidemiological/pathological and forensic aspects of sudden infant death from Stockholm during the 1840s. SIDS means that neither anamnesis nor a thorough autopsy can explain the death. SIDS may be considered a dysfunction syndrome, in which endogenous and exogenous factors act together and silently lead to death.(ABSTRACT TRUNCATED AT 400 WORDS)

Thermal stress in sudden infant death: Is there an ambiguity with the rebreathing hypothesis?

OBJECTIVE

To assess the role of thermal stress in the cause of sudden infant death syndrome (SIDS), and to compare risk factors with those of rebreathing.

METHODOLOGY

Analysis of publications concerning the epidemiology and physiology of thermal stress in SIDS.

RESULTS

A strong association between thermal regulation and ventilatory control was found, specifically for prolonged apnea. Infections, excessive room heat and insulation, and prone sleeping produce significantly increased odds ratios for SIDS. Although some of the risk factors for rebreathing could be explained by the effects of thermal stress, several factors for thermal stress could not reasonably be explained by the rebreathing hypothesis.

CONCLUSIONS

Although the risk of thermal stress is widely accepted abroad, it has received relatively little attention in the United States. The incidence of SIDS in the United States can likely be further reduced by educating the public against the dangers of overheating, as an integral part of the back-to-sleep campaign.

Influence of core temperature on autoresuscitation during repeated exposure to hypoxia in normal rat pups

Failure to autoresuscitate by hypoxic gasping during prolonged sleep apnea has been suggested to play a role in sudden infant death. Furthermore, thermal stress brought about by a contribution of infection, overwrapping, or excessive environmental heating has been shown to be associated with an increased risk of sudden infant death, particularly in prone sleeping infants. The present experiments were carried out on newborn rat pups to investigate the influence of "forced" changes in core temperature on their time to last gasp during a single hypoxic exposure and on their ability to autoresuscitate during repeated exposure to hypoxia. On day 5 or 6 postpartum the pups were placed in a temperature-controlled chamber regulated to 33, 35, 37, 39, or 41 degrees C and exposed to a single period of hypoxia (97% N(2)-3% CO(2)) and their time to last gasp was determined, or they were exposed repeatedly to hypoxia and their ability to autoresuscitate from primary apnea was determined. Increases in core temperature brought about by changes in ambient temperature from 33 to 41 degrees C decreased the time to last gasp after a single hypoxic exposure and decreased the number of successful autoresuscitations after repeated hypoxic exposures. Thus our data support the hypothesis that forced changes in core temperature brought about by changes in ambient temperature influence protective responses in newborns that may prevent death during hypoxia, as may occur during single or repeated episodes of prolonged sleep apnea.

Thermal environment and sudden infant death syndrome: case-control study

OBJECTIVE

To compare the thermal environment of infants who died of the sudden infant death syndrome with that of age matched control infants.

DESIGN

Case-control study. Infants who died were matched with two controls, one for age and one for age and birth weight. Thermal measurements were conducted at the death scene for cases and at the scene of last sleep for control infants, who were visited unexpectedly within four weeks of the index infant's death on a day of similar climatic conditions. A follow up questionnaire was administered to parents of cases and controls.

SETTING

The geographical area served by the professional Tasmanian state ambulance service, which includes 94% of the Tasmanian population.

SUBJECTS

41 infants died of the sudden infant death syndrome at home; thermal observations at death scene were available for 28 (68%), parental questionnaire data were available for 40 (96%). 38 controls matched for age and 41 matched for age and birth weight.

RESULTS

Cases had more excess thermal insulation for their given room temperature (2.3 togs) than matched controls (0.6 togs) (p = 0.009). For every excess thermal insulation unit (tog) the relative risk of the sudden infant death syndrome was 1.26 (95% confidence interval 1.05 to 1.52). The average thermal bedding value calculated from parental recall was similar to that observed by attendant ambulance officers (mean difference = 0.4 tog, p = 0.39). Cases were more likely to have been found prone (odds ratio 4.58; 1.48 to 14.11). Prone sleeping position was not a confounder or effect modifier of the relation between excess thermal insulation and the syndrome.

CONCLUSIONS

Overheating and the prone sleeping position are independently associated with an increased risk of the sudden infant death syndrome. Further work on infant thermal balance and sudden infant death is required and guidelines for appropriate infant thermal care need to be developed.

Sudden infant death. Overheating and cot death

Four risk factors for overheating were sought in the histories of 34 cot-death victims in Oxford and Scarborough. 19 babies were unusually hot or sweating when found dead; 14 died in an unusually warm environment; 17 had evidence of a terminal infective illness; and 24 were excessively clothed or overwrapped. 3 babies had all four risk factors, 8 had three, 17 had two, and 4 had one risk factor. Only 2 had no risk factor; both had had very low birthweights. In 6 of 15 babies (40%) whose rectal temperature was recorded after death the temperature was above 37 degrees C, the highest being 42 degrees C. If parents could be educated to anticipate the dangerous situations preceding febrile apnoea, many cot deaths could probably be avoided.