The hypothesis that the prone sleeping position is associated with acc
umulation of upper airways secretions and increased bacterial growth w
as investigated in adults. Ten subjects with upper respiratory tract i
nfection lay prone for one hour and then supine for one hour. Nasal sw
abs after the prone period yielded higher bacterial counts than swabs
obtained after the supine period. This result could be relevant to sud
den infant death syndrome (SIDS), as infants who sleep in the prone po
sition are at increased risk of SIDS and one theory is that death is c
aused by toxins produced by bacterial overgrowth in the upper respirat
ory tract following a viral infection.