The minimal disease severity at which patients with the sleep apnea/hypopnea syndrome (SAHS) gain benefit from treatment is not well characterized, although a pilot study of continuous positive airway pressure (CPAP) therapy showed daytime improvements in patients with 5 to 15 apneas + hypopneas per hour slept (AHI). We have thus performed a second, larger, randomized, placebo- controlled study in a prospective series of 34 patients (13 female) with mild SAHS (AHI 5 to 15) and daytime sleepiness. Patients spent 4 wk on CPAP treatment and 4 wk on an oral placebo, with randomization of treatment order, and daytime assessments on the last day of each treatment. Effective CPAP use averaged 2.8 +/- 2.1 h (mean +/- SD) per night. Compared with placebo, CPAP improved symptom score (p< 0.01), subjective (Epworth; p < 0.01) but not objective (maintenance of wakefulness test; p > 0.2) sleepiness, performances on 2 of 7 cognitive tasks (p < 0.02), depression score (p < 0.01), and five subscales of the SF-36 health/functional status questionnaire (p

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Around 50% of patients with the sleep apnea/hypopnea syndrome (SAHS) are not obese: body mass index (BMI) < 30 kg/m2. We hypothesized that local fat deposition around the upper airway may be different in nonobese patients with SAHS from that in normal subjects with the same body mass. We therefore examined the relationship between indices of general obesity; BMI, neck circumference (NC), and percentage total body fat with neck fat deposition measured by magnetic resonance imaging in three matched subject groups. Nine nonobese, nonsnoring control subjects (BMI, 25 SE 0.7 kg/m2; 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/m2; NC, 39.8 SE 0.8 cm; age, 40 SE 4.2 yr), and nine obese patients with SAHS matched to the other groups for age (BMI, 34 SE 1.1 kg/m2; NC, 43.9 SE 0.6 cm; age, 40 SE 2.7 yr). Neck volume and fat content were assessed from the hard palate to the vocal cords using T1-weighted images. Percentage total body fat was 30 and 44% greater in nonobese and obese patients with SAHS, respectively, than in control subjects. Neck tissue volume was 10% greater in nonobese and 28% greater in obese patients with SAHS than in control subjects. The percentage of neck tissue volume attributed to fat was 27% greater in nonobese and 67% greater in obese patients with SAHS than in control subjects. The excess fat in both the nonobese and obese patients with SAHS compared with that in control subjects was localized to areas anterolateral to the upper airway, the differences were 52 and 88%, respectively. There were no significant differences between nonobese patients with SAHS and control subjects with respect to fat located in other areas of the neck; obese patients with SAHS had 42% more fat than control subjects (p < 0.05). We conclude that even relatively nonobese patients with SAHS have excess fat deposition, especially anterolateral to the upper airway when compared with control subjects with the same level of obesity assessed using BMI and NC. This may contribute to their predisposition to SAHS.

Background-Obesity and increased neck circumference are risk factors for the obstructive sleep apnoea/hypopnoea syndrome (SAHS). SAHS is more common in men than in women, despite the fact that women have higher rates of obesity and greater overall body fat. One factor in this apparently paradoxical sex distribution may be the diVering patterns of fat deposition adjacent to the upper airway in men and women. A study was therefore undertaken to compare neck fat deposition in normal men and women. Methods-Using T1 weighted magnetic resonance imaging, the fat and tissue volumes in the necks of 10 non-obese men and 10 women matched for age (men mean (SE) 36 ( Conclusions-There are diVerences in neck fat deposition between the sexes which, together with the greater overall soft tissue loading on the airway in men, may be factors in the sex distribution of SAHS. (Thorax 1999;54:323-328) Keywords: sleep apnoea; neck fat; sex diVerences; magnetic resonance imaging Sleep disordered breathing, snoring, and the sleep apnoea/hypopnoea syndrome (SAHS) are 2-8 times more common in men than in women in all adult age groups.1 2 In men these conditions are associated with obesity, increased neck circumference, and reduced cross sectional area of the upper airway, 3-6 all factors which predispose to the partial or complete obstruction of the upper airway.The male predominance in SAHS has not been fully explained and is in some respects paradoxical. Compared with men, a greater proportion of total body soft tissue in normal women is fat and obesity is more frequent in women.7 8 A condition strongly associated with obesity might therefore be predicted to show a higher frequency in women. Similarly, pharyngeal airway cross sectional area has been reported to be less in women when matched for body mass index (BMI), 9 which would be expected to predispose to airway obstruction. However, women do have a smaller neck circumference when matched for BMI and so overall mass loading on the upper airway may be less.10 Dynamic factors are also relevant; the upper airway when seated is smaller in women, but there is no diVerence between supine men and women. 10 This suggests that women have a greater ability to defend the airway against posture related changes, and a higher waking upper airway dilating muscle tone in women may provide a physiological basis for this. 11Magnetic resonance imaging (MRI) has become an established method for the in vivo quantification of fat tissue.12 13 Fat has a relatively short T1 relaxation time, so fatty tissue has a higher intensity than other soft tissues in T1 weighted spin echo MRI images. The availability of this technique has prompted a number of studies which have attempted to clarify the relationship between obesity and upper airway obstruction at a detailed anatomical level. Although there is a clear relationship between overall neck size and airway obstruction in men, 3 there is still controversy about the significance of the precise anatomical distribution of fat deposition in the neck. Ho...