Three studies provided data on the serum leptin levels in OSA patients diagnosed by portable device, and the results reveal that that the serum leptin levels were higher in these OSA patients than in the controls (WMD=3.12 ng/ml, 95%CI=0.64-5.59, P=0.013) (Table 3). The gene discussed is LEP; the disease is obstructive sleep apnea syndrome.