Vol. 123, No. 7 News | Science SelectionsOpen AccessNew Risk Factor for SIDS? Peaks in Cot Deaths Associated with Heat Waves Carrie Arnold Carrie Arnold Search for more papers by this author Published:1 July 2015https://doi.org/10.1289/ehp.123-A185Cited by:1View Article in:中文版AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit It’s every parent’s worst nightmare: A healthy infant goes down for a nap but never wakes up. Researchers have begun to identify a number of risk factors for sudden infant death syndrome (SIDS, also known as cot death), including swaddling, dressing the infant too warmly, and other behaviors that may cause the sleeping child to overheat.1 In this issue of EHP, the authors of a new study of SIDS deaths report that hotter outdoor temperatures also may be a risk factor.2SIDS deaths peak in infants between ages 2 and 4 months, and then decline,3 with males more likely to be affected than females.4 In 1994 the National Institute of Child Health and Human Development launched the Back to Sleep campaign (now known as the Safe to Sleep® campaign), which urged new parents to place their infants to sleep on their backs.5 Side- or stomach-sleeping can constrict a newborn’s airways, causing a dangerous drop in oxygen levels.6 (Stomach-sleeping may also interfere with a baby’s ability to regulate his body temperature, because a good deal of heat loss occurs through the face.1)Overheating is one of the chief risk factors for SIDS. Parents should dress their babies warmly but not go overboard with clothing and blankets.© David Nigel Owens/Getty ImagesThe campaign was a tremendous success—in its first 10 years, U.S. SIDS rates decreased by more than 50%. However, rates have since plateaued,7 and an estimated 2,300 babies still die of SIDS each year in the United States.8Although older children are able to rouse themselves and shift their sleeping position to regain adequate oxygen levels, these abilities are underdeveloped in very young infants.9 A baby’s thermoregulatory system also has not reached maturity. “Infants are not like adults; they don’t have the same ability to regulate temperature through sweating,” says Nathalie Auger, an epidemiologist at the Québec Public Health Institute and lead author of the new EHP study.A 1993 study first linked infant thermoregulation and respiratory control to SIDS,10 and in 2008 scientists reported that the use of a fan in an infant’s bedroom appeared to help reduce SIDS risk.11 These studies, Auger believed, hinted that extreme heat events also might increase SIDS risk, although no one had actually tested that.Auger and colleagues identified 196 certified cases of SIDS in metropolitan Montreal in April through October for the years 1981 through 2000. To analyze the effects of heat, the researchers used a case-crossover design, where each case of SIDS served as its own control. For each SIDS case, the researchers ascertained the maximum temperatures on the day of and the day before death. Then they compared these temperatures with the maximum temperatures of matched control days. Control days were chosen on the basis of each infant’s death date, such that for a child who died on a Saturday in July 2000, for instance, control days would consist of all the other Saturdays in that month. This study design allowed the researchers to control for confounders such as secondhand smoke exposure, birth weight, and sleep environment.On the hottest days, when the temperature exceeded 29°C (84.2°F), infants had 2.78 times greater odds of dying from SIDS compared with days when the temperature was 20°C (68.0°F). The relationship between higher temperatures and SIDS was stronger for babies aged 3–12 months compared with those aged 1–2 months, with odds ratios of 3.90 and 1.73, respectively, for deaths on days with maximum temperatures of 29°C versus 20°C.2“I have to congratulate the authors on doing SIDS research—it’s not an easy task,” says De-Kun Li, a senior research scientist at the Kaiser Permanente Northern California Division of Research, who was not involved in the study. However, he points out an important limitation of the study: Although the authors measured outdoor temperatures, they didn’t measure the actual temperature of the room in which the baby slept. Plenty of SIDS deaths occur in winter when babies are dressed too warmly, and the same could occur during heat waves when houses may be air-conditioned to the point of chilliness, he says.“Understanding causes for SIDS remains a work in progress,” Li says. “It’s very hard to study.”References1 Guntheroth WG, Spiers PSThermal stress in sudden infant death: is there ambiguity with the rebreathing hypothesis?Pediatrics 107(4):693-6982001.; PMID:11335746. Crossref, Medline, Google Scholar2 Auger Net al.Ambient heat and sudden infant death: a case-crossover study spanning 30 years in Montreal, Canada.Environ Health Perspect 123(7):712-7162015.; doi:10.1289/ehp.130796025748025. Link, Google Scholar3 Filiano JJ, Kinney HCA perspective on neuropathologic findings in victims of the sudden infant death syndrome: the triple risk model.Biol Neonate 65(3-4):194-1971994.; doi:10.1159/0002440528038282. Crossref, Medline, Google Scholar4 Blair PSet al.Major epidemiological changes in sudden infant death syndrome: a 20-year population-based study in the UK.Lancet 367(9507):314-3192006.; doi:10.1016/S0140-6736(06)67968-316443038. Crossref, Medline, Google Scholar5 Safe to Sleep® Public Education Campaign [website]. Bethesda, MD:Eunice Kennedy Shriver National Institute of Child Health and Human Development (updated 2 January 2015). Available: http://www.nichd.nih.gov/sts/Pages/default.aspx [accessed 16 June 2015]. Google Scholar6 Adams SMet al.Sudden infant death syndrome.Am Fam Physician 91(11):778-7832015., PMID:26034855. Medline, Google Scholar7 Hauck FR, Tanabe KOInternational trends in sudden infant death syndrome: stabilization of rates requires further action.Pediatrics 122(3):660-6662008.; doi:10.1542/peds.2007-013518762537. Crossref, Medline, Google Scholar8 Trachtenberg FLet al.Risk factor changes for sudden infant death syndrome after initiation of Back-to-Sleep campaign.Pediatrics 129(4):630-6382012.; doi:10.1542/peds.2011-141922451703. Crossref, Medline, Google Scholar9 Willinger Met al.Infant sleep position and risk for sudden infant death syndrome: report of meeting held January 13 and 14, 1994, National Institutes of Health, Bethesda, MD.Pediatrics 93(5):814-8191994.; PMID:8165085. Medline, Google Scholar10 Fleming PJet al.Interactions between thermoregulation and the control of respiration in infants: possible relationship to sudden infant death.Acta Paediatr Suppl 82(suppl 390):57-591993.; doi:10.1111/j.1651-2227.1993.tb128788374195. Crossref, Medline, Google Scholar11 Coleman-Phox Ket al.Use of a fan during sleep and the risk of sudden infant death syndrome.Arch Pediatr Adolesc Med 162(10):963-9682008.; doi:10.1001/archpedi.162.10.96318838649. Crossref, Medline, Google ScholarFiguresReferencesRelatedDetailsCited By Waldhoer T, Heinzl H and Räisänen S (2017) Exploring the possible relationship between ambient heat and sudden infant death with data from Vienna, Austria, PLOS ONE, 10.1371/journal.pone.0184312, 12:9, (e0184312) Vol. 123, No. 7 July 2015Metrics About Article Metrics Publication History Originally published1 July 2015Published in print1 July 2015 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. 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