Increased airway smooth muscle in sudden infant death syndrome

The underlying pathophysiological mechanism behind death in the sudden infa nt death syndrome (SIDS) is uncertain. Although infants dying of SIDS frequ ently have a postmortem examination performed, no specific diagnostic patho logy in any organ system has been identified. Previous theories relating to the cause of death in SIDS have included increased lower airway closure. W e examined the airway morphometry of 57 infants who died of SIDS and compar ed these findings with those obtained from 21 age-matched infants who had d ied of non-SIDS causes. Airway wall dimensions, epithelial thickness, and t he area of smooth muscle within the airway wall were measured. Airways from infants who died of SIDS showed a significantly higher proportion of airwa y smooth muscle than control airways when corrected for age and sex (p < 0. 01). There was no significant difference between the groups for wall thickn ess or epithelial thickness. Increased airway smooth muscle in infants who have died of SIDS may contribute to excessive airway narrowing, raising the possibility that the cause of death in this condition is related to abnorm alities in lower airway function.