The serum leptin level in non-obese patients with obstructive sleep apnea.

OBJECTIVE: This study aimed to determine the association between the severity of obstructive sleep apnea (OSA) and the serum leptin level in non-obese OSA patients. METHODS: This prospective case-control study included non-obese OSA patients that presented with sleep-related disturbances and underwent polysomnography (PSG) between April 2015 and June 2016. The serum leptin level was measured and its relationship to PSG parameters was investigated. RESULTS: The study included 73 OSA patients (20 female and 53 male) with a mean age of 41.1±11.5 years and mean body-mass index (BMI) of 26.4±2.7kgm-2. The serum leptin level in 44 patients with moderate/severe OSA (AHI ≥15) was 3.4±2.6ngmL-1, versus 4.5±3.8ngmL-1 in 29 patients with snoring/mild OSA (AHI <15) (P=0.20). There were not any correlations between any of the PSG parameters and the serum leptin level, but there was a significant correlation between the leptin level and BMI (r=0.345, P<0.01). CONCLUSION: The serum leptin level does not differ significantly between non-obese OSA patients with moderate/severe and snoring/mild OSA. Obesity is the primary factor associated with the serum leptin level.