Sudden infant death syndrome (SIDS) is a leading cause of infant mortality in the United States. While thermal stress is implicated in many risk factors for SIDS, the association between ambient temperature and SIDS remains unclear.
We obtained daily individual-level infant mortality data and outdoor temperature data from 1972 to 2006 for 210 US cities. We applied a time-stratified case–crossover analysis to determine the effect of ambient temperature on the risk of SIDS by season. We stratified the analysis by race, infant age, and climate.
There were a total of 60,364 SIDS cases during our study period. A 5.6°C (10°F) higher daily temperature on the same day was associated with an increased SIDS risk of 8.6% (95% confidence interval [CI] = 3.6%, 13.8%) in the summer, compared with a 3.1% decrease (95% CI = −5.0%, −1.3%) in the winter. Summer risks were greater among black infants (18.5%; 95% CI = 9.3%, 28.5%) than white infants (3.6%; 95% CI = −2.3%, 9.9%), and among infants 3–11 months old (16.9%; 95% CI = 8.9%, 25.5%) than infants 0–2 months old (2.7%; 95% CI = −3.5%, 9.2%). The temperature–SIDS association was stronger in climate clusters in the Midwest and surrounding northern regions.
Temperature increases were associated with an elevated risk of SIDS in the summer, particularly among infants who were black, 3 months old and older, and living in the Midwest and surrounding northern regions.
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From the aHarvard Medical School, Boston, MA; bDepartment of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA; cDepartment of Pathology, Brigham and Women’s Hospital, Boston, MA; and dDivision of Cardiovascular Medicine, Brigham and Women’s Hospital, Boston, MA.
Submitted November 16, 2016; accepted June 22, 2017.
This work was supported by NIEHS grant R21ES024012 and P30 ES000002, NIH grant P50MD010428-01, and US EPA grant 83615601-0.
The authors report no conflicts of interest.
Data availability: Because the mortality dataset was used under a Data User Agreement from each state, the dataset and code are not available for replication.
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Correspondence: Iny Jhun, Harvard Medical School, 25 Shattuck Street, Boston, MA 02215. E-mail: email@example.com.