1. Worth, Tammy


The roles of serotonin and other risk factors are assessed.


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Sudden infant death syndrome (SIDS), the "sudden death of an infant younger than one year that remains unexplained after a complete autopsy and death scene investigation," is still the leading cause of death in children one month to one year of age. Two recent studies attempt to shed more light on this heartbreaking subject.

Figure. Photo courte... - Click to enlarge in new windowFigure. Photo courtesy of the Back to Sleep campaign, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Heath and Human Services (

In the first report, Duncan and colleagues, whose earlier research had revealed serotonin-binding abnormalities in the medulla oblongata of infants who had died of SIDS, proposed that the abnormality "causes an inability to restore homeostasis following life-threatening challenges" (asphyxia) and hypothesized that "SIDS is associated with reductions in tissue levels" of serotonin, its biosynthetic enzyme tryptophan hydroxylase (THP2), or both. After examining tissue samples from 41 infants who had died of SIDS, seven who had died from other known causes (controls), and five who had been hospitalized with "chronic oxygenation disorders . . . prior to death," the scientists found that serotonin levels were 26% lower in children who died of SIDS, compared with the control children; THP2 levels were 22% lower in the SIDS victims than in controls (although they were even lower in the hospitalized group). The authors call for research that focuses on the underproduction of serotonin and THP2 and suggest that deficiencies may appear as early as the first trimester; further, that the deficiencies are partial could explain why infants don't manifest the problems "during waking but are unable to respond to homeostatic stressors during sleep when the partial deficit is potentially unmasked. . . ."


The second study examined known risk factors-specifically, the frequency with which they occur and with which they appear together, and the frequency of cases in which there appear to be no risk factors. In a population-based, retrospective database review, Ostfeld and colleagues examined five years' worth of SIDS cases in New Jersey. They found only two cases that were definitively associated with no known risk factors for SIDS. In contrast, 96% of cases were associated with at least one risk factor, and multiple risk factors (many of which were modifiable) were present in 78% of cases. For instance, nonsupine sleep positioning (or shifting to a prone position) occurred in 70% of cases, and in 76% and 75% of those cases, respectively, the mother or the father had smoked; bed sharing took place in 80% of cases in which nonsupine sleep was present. Nonmodifiable risk factors, such as upper respiratory infections and premature birth, often occurred with modifiable ones. The study authors hope that these findings will give providers a better picture of the issue as a whole and the importance of educating parents on reducing the risk of SIDS.


Tammy Wortht


Duncan JR, et al. JAMA 2010;303(5):430-7;


Ostfeld BM, et al. Pediatrics 2010;125(3):447-53.