Although most patients with obstructive sleep apnea (OSA) are obese, i
t is not known how obesity contributes to airway collapse during sleep
. The purpose of this study was to determine whether the volume of adi
pose tissue adjacent to the pharyngeal airway in humans is related to
the degree of OSA. We studied 30 subjects, nine without OSA and 21 wit
h OSA; two subjects were studied before and after weight loss. Adipose
tissue was detected with magnetic resonance imaging using T1-weighted
spin echo sequences. The volume of adipose tissue adjacent to the upp
er airway was determined by measuring the volume of all pixels in the
intensity range of adipose tissue within the region bounded by the ram
us of the mandible, the spine, the anterior border of the soft palate,
and the hard palate. Polysomnography was performed with conventional
techniques. All subjects had a collection of adipose tissue adjacent t
o the upper airway; the volume of this adipose tissue correlated with
the number of apneas plus hypopneas per hour of sleep (r = 0.59, p < 0
.001). Both patients who lost weight and had fewer apneas and hypopnea
s had a marked decrease in the pharyngeal adipose tissue volume. We co
nclude that adipose tissue is deposited adjacent to the pharyngeal air
way in patients with OSA and that the volume of this tissue is related
to the presence and degree of OSA.