1. There was a significantly increased risk of sudden infant death syndrome among infants who resided above 8000 feet compared to those below 6000 feet, in the state of Colorado between 2007 and 2012.
2. The national Back to Sleep public health campaign produced a significant decrease in the incidence of sudden infant death syndrome in Colorado. This effect persisted to a similar degree across all residential altitudes.
Evidence Rating Level: 2 (Good)
Study Rundown: Sudden infant death syndrome (SIDS) is the third leading cause of death among infants in the United States. Several factors have been repeatedly associated with SIDS, such as maternal smoking, low socioeconomic status (SES) and sleeping in the prone position. Smaller studies have begun to uncover the connection between hypoxia and SIDS, and even fewer have investigated the potential connection between altitude-associated hypoxia and SIDS. The secondary aim explored the effect of the nationally successful Back to Sleep campaign on the incidence of SIDS in Colorado. Overall, compared with infants residing at <6000 feet, there was a significantly increased risk of SIDS in infants living at >8000 feet. Living between 6000 and 8000 feet was not associated with increased incidence of SIDS compared to those living below 6000 feet. The Back to Sleep campaign was successful in significantly decreasing the incidence of SIDS in the post-implementation time period. This decrease was proportional among all residential altitudes. This study begins to uncover an additional, somewhat modifiable, risk factor for SIDS, which may inform future public health campaigns to further reduce the incidence of SIDS. While this study makes headway in uncovering important risk factors for SIDS, it was limited by the range of assessed altitudes and geographic location.
In-Depth [retrospective cohort]: This study used the Colorado birth certificate and infant death registries data from 1990 through 2012 for both their primary and secondary analysis. The primary analysis included all infant deaths from 2007 through 2012 (n = 393 216). Altitude was obtained from the maternal residence at the time of infant birth and was divided into 3 categories, <6000 feet, between 6000 and 8000 feet and >8000 feet. Overall incidence of SIDS was 0.42/1000 live births and was lowest among infants at <6000 feet (0.40/1000) and highest among those living at >8000 feet (0.79/1000). Compared to infants living at <6000 feet, those living between 6000 and 8000 did not have increased odds of SIDS. Infants living at >8000 feet had a statistically significant higher associated with SIDS compared to those living <6000 feet (OR 2.29 95% CI 1.01-5.22). In order to compare pre- and post-Back to Sleep births for the secondary analysis, data from 1990-1993 was compared with data from 1997-2012. After implementation of this policy, there was a significant decrease in the incidence of SIDS from 1.99/1000 to 0.57/1000. This decrease was statistically significant and uniform across all altitude levels.
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