Background
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.
Methods
We obtained daily individual-level infant mortality data and outdoor temperature data from 1972 to 2006 for 210 United States 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.
Results
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 to 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.
Conclusions
Temperature increases were associated with an elevated risk of SIDS in the summer, particularly among infants who were Black, 3 months and older, and living in the Midwest and surrounding northern regions.