NECK AND TOTAL-BODY FAT DEPOSITION IN NONOBESE AND OBESE PATIENTS WITH SLEEP-APNEA COMPARED WITH THAT IN CONTROL SUBJECTS

Around 50% of patients with the sleep apnea/hypopnea syndrome (SAHS) a re not obese: body mass index (BMI) < 30 kg/m(2). We hypothesized that local fat deposition around the upper airway may be different in nono bese patients with SAHS from that in normal subjects with the same bod y mass. We therefore examined the relationship between indices of gene ral obesity; BMI, neck circumference (NC), and percentage total body f at with neck fat deposition measured by magnetic resonance imaging in three matched subject groups. Nine nonobese, nonsnoring control subjec ts (BMI, 25 SE 0.7 kg/m(2); NC, 38.1 SE 0.5 cm; age, 37.5 SE 2.5 yr), nine nonobese patients with SAHS (BMI, 25.7 SE 0.4 kg/m(2); NC, 39.8 S E 0.8 cm; age, 40 SE 4.2 yr), and nine obese patients with SAHS matche d to the other groups for age (BMI, 34 SE 1.1 kg/m(2); NC, 43.9 SE 0.6 cm; age, 40 SE 2.7 yr). Neck volume and fat content were assessed fro m the hard palate to the vocal cords using T1-weighted images. Percent age total body fat was 30 and 44% greater in nonobese and obese patien ts with SAHS, respectively, than in control subjects. Neck tissue volu me was 10% greater in nonobese and 28% greater in obese patients with SAHS than in control subjects. The percentage of neck tissue volume at tributed to fat was 27% greater in nonobese and 67% greater in obese p atients with SAHS than in control subjects, The excess fat in both the nonobese and obese patients with SAHS compared with that in control s ubjects was localized to areas anterolateral to the upper airway, the differences were 52 and 88%, respectively. There were no significant d ifferences between nonobese patients with SAHS and control subjects wi th respect to fat located in other areas of the neck; obese patients w ith SAHS had 42% more fat than control subjects (p < 0.05). We conclud e that even relatively nonobese patients with SAHS have excess fat dep osition, especially anterolateral to the upper airway when compared wi th control subjects with the same level of obesity assessed using BMI and NC. This may contribute to their predisposition to SAHS.