Study objectives: To define the metabolic profile
relevant to vascular risks in obstructive sleep apnea (OSA) and the
role of leptin resistance in this risk profile.
Design: Case control study.
Laboratory, Queen Mary Hospital, University of Hong Kong, China.
Methods: Thirty OSA subjects were matched with 30 non-OSA
subjects for body mass index (BMI), age, sex, and menopausal status.
Neck, waist, and hip girth, skinfold thickness, and fasting serum
levels of lipids, glucose, insulin, and leptin were compared between
these two groups.
Results: Compared with control
subjects with a similar BMI but without OSA, the OSA group had a
significantly more adverse vascular risk factor profile, including
dyslipidemia, higher diastolic BP, insulin resistance, and greater
adiposity reflected by skinfold thickness. OSA subjects also had higher
circulating leptin levels (9.18 ± 4.24 ng/mL vs 6.54 ± 3.81
ng/mL, mean ± SD, p = 0.001). Serum leptin levels correlated
positively with BMI, skinfold thickness, serum cholesterol, low-density
lipoprotein cholesterol, insulin, insulin/glucose ratio, apnea-hypopnea
index, and oxygen desaturation time; multiple stepwise regression
analysis identified skinfold thickness, waist/hip ratio, serum
low-density lipoprotein cholesterol, and diastolic BP as independent
correlates, while only serum insulin and diastolic BP were independent
correlates in OSA subjects. After treatment with nasal continuous
positive airway pressure for 6 months, there was a significant decrease
in circulating leptin (p = 0.01) and triglyceride levels (p = 0.02)
without change in other parameters.
Despite controlling for BMI, OSA subjects showed distinct profiles with
clustering of vascular risk factors. Hyperleptinemia was present in the
OSA subjects, but it can be normalized by treatment with nasal
continuous positive airway pressure, suggesting that increased leptin
resistance was not the cause of OSA or its associated vascular