Sudden infant death syndrome and residential altitude

Abstract

Background: Theories of sudden infant death syndrome (SIDS) suggest hypoxia is a common pathway. Infants living at altitude have evidence of hypoxia; however, the association between SIDS incidence and infant residential altitude has not been well studied.

Methods: We performed a retrospective cohort study by using data from the Colorado birth and death registries from 2007 to 2012. Infant residential altitude was determined by geocoding maternal residential address. Logistic regression was used to determine adjusted association between residential altitude and SIDS. We evaluated the impact of the Back to Sleep campaign across various altitudes in an extended cohort from 1990 to 2012 to assess for interaction between sleep position and altitude.

Results: A total of 393 216 infants born between 2007 and 2012 were included in the primary cohort (51.4% boys; mean birth weight 3194 ± 558 g). Overall, 79.6% infants resided at altitude <6000 feet, 18.5% at 6000 to 8000 feet, and 1.9% at >8000 feet. There were no meaningful differences in maternal characteristics across altitude groups. Compared with residence <6000 feet, residence at high altitude (>8000 feet), was associated with an adjusted increased risk of SIDS (odds ratio 2.30; 95% confidence interval 1.01-5.24). Before the Back to Sleep campaign, the incidence of SIDS in Colorado was 1.99/1000 live births and dropped to 0.57/1000 live births after its implementation. The Back to Sleep campaign had similar effect across different altitudes (P = .45).

Conclusions: Residence at high altitude was significantly associated with an increased adjusted risk for SIDS. Impact of the Back to Sleep campaign was similar across various altitudes.

FIGURE 1

SIDS incidence per 1000 live births stratified by residential altitude. Incidence per 1000 live births (95% Wald Confidence Limits).

FIGURE 2

Incidence of SIDs, accidental suffocation, and death of unknown cause per 1000 live births stratified by residential altitude. Incidence per 1000 live births (95% Wald Confidence Limits): <6000 feet: SIDS 0.40 (0.34–0.48); unknown 0.19 (0.15–0.24); accidental suffocation 0.11 (0.08–0.16). 6000–8000 feet: SIDS 0.45(0.32–0.64); unknown 0.17 (0.09–0.29); accidental suffocation 0.12 (0.06–0.24). >8000 feet: SIDS 0.79 (0.35–0.1.75); unknown 0.13 (0.02–0.93); accidental suffocation 0.13 (0.02–0.93).

FIGURE 3

Incidence of SIDS and all-cause infant mortality in the pre– and post–Back to Sleep era. Pre–Back to Sleep era includes 1990 to 1993 and post–Back to Sleep era includes 1997 to 2012. Rates of SIDS and all-cause infant mortality reported per 1000 live births.