Positive association of plasma leptin with sleep quality in obese type 2 diabetes patients

Aims/Introduction Poor sleep quality is associated with obesity and diabetes. The adipocyte‐derived hormone, leptin, was recently shown to underlie the link between abnormal sleep and obesity. We aimed to investigate the association between leptin and sleep quality in type 2 diabetes patients. Materials and Methods In the present cross‐sectional study, we studied 182 type 2 diabetes patients, among whom 113 were diagnosed with obesity (body mass index ≥25 kg/m2). Fasting plasma leptin levels were measured, and sleep architecture was assessed using single‐channel electroencephalography. Results Using unadjusted analyses, the obese type 2 diabetes patients, but not their non‐obese counterparts, showed a positive correlation between plasma leptin levels and a parameter for deep sleep assessed by delta power during the first sleep cycle. Multivariate analysis showed that plasma leptin levels were positively associated with delta power, but not with the total sleep time, after adjusting for potential confounders including age, body mass index and the apnea–hypopnea index, in the obesity group. However, neither delta power nor total sleep time was associated with leptin in the non‐obesity group. Conclusions Plasma leptin levels are independently associated with sleep quality in obese, but not in non‐obese, type 2 diabetes patients. The present study indicates a favorable relationship between leptin and sleep quality in obese type 2 diabetes patients.