Background: Obstructive sleep apnea-hypopnea syndrome (OSAHS) is characterized by repeated oxygen desaturation. Obesity and visceral fat accumulation (VFA) are risk factors for the development of OSAHS. Circulating leptin increases in accordance with body mass index (BMI), and under experimental conditions intermittent hypoxia stimulates leptin production.
Methods: The primary objective of this study was to investigate whether hypoxemia during sleep influences the levels of circulating leptin and whether the location of body fat deposits, ie, the distribution of VFA and subcutaneous fat accumulation (SFA), affects circulating leptin levels in patients with OSAHA who are not obese. We assessed VFA and SFA by abdominal CT scan and measured circulating levels of leptin in 96 male patients with OSAHS and 52 male patients without OSAHS matched for BMI. To be matched for BMI in the two groups, patients whose BMIs were < 27 were selected for the OSAHS group.
Results: In the whole study group, circulating leptin levels correlated with BMI (r = 0.30), VFA (r = 0.44), SFA (r = 0.28), apnea-hypopnea index (AHI) [r = 0.48], sleep mean arterial oxygen saturation (Sao2) [r = 0.59], and sleep lowest Sao2 (r = 0.37). Multiple regression analysis showed that average Sao2 (p < 0.01) and lowest Sao2 (p = 0.03) were explanatory variables for serum leptin values, but AHI (p = 0.054), BMI (p = 0.33), VFA (p = 0.11), and SFA (p = 0.36) were not.
Conclusions: These results suggest that sleep hypoxemia may be the main determinant of circulating leptin levels, although the location of body fat deposits could contribute to the elevated circulating leptin levels in patients with OSAHS who are not obese.