High frequency spectral power of sleep EEG increases with depressive and insomnia symptoms in kidney transplant recipients

Abstract

The prevalence of depression and insomnia is high among kidney transplant recipients and the co-occurence of the two disorders is frequent. Hyperarousal of the central nervous system (CNS) might play a role in the pathomechanism of both conditions. The hypervigilant state of the CNS is characterized by heightened beta- and gamma spectral power of the EEG. We investigated whether depressive and isomnia symptoms correlate with high frequency spectral power among kidney transplant recipients. Fitfy-six kidney tranplant recipients participated in the study (35 males, mean age 49 ± 13 years, BMI 26 ± 4 kg/m 2 , estimated glomerular filtration rate 50 ± 17 ml/min). Symptoms of insomnia and depression were measured by the Athens Insomnia Scale (AIS) and the Center for Epidemiologic Studies Depression Scale (CESD), respectively. After one-night polysomnography (PSG) each recording was visually scored and EEG absolute spectral power was computed within the sigma (11.25–15 Hz), beta1 (15.25–25 Hz), beta2 (25.25–35 Hz), and gamma (35.25–45 Hz) frequency bands. AIS score correlated with sleep latency ( r = 0.274, p < 0.05) among the PSG macrostructure parameters while CESD score did not correlate with any PSG variables. CESD score correlated with NREM and REM gamma ( r = 0.35; r = 0.27), beta2 ( r = 0.28; r = 0.3), beta1 ( r = 0.32; r = 0.27) spectra, respectively. AIS score correlated with NREM and REM gamma ( r = 0.27; r = 0.31), beta2 ( r = 0.27; r = 0.44), NREM sigma ( r = 0.29) and REM beta1 ( r = 0.37) spectra, respectively ( p < 0.05 for each correlation). In multivariable linear model after controlling for age, gender, kidney function and BMI, the CESD score was an independent predictor of NREM gamma (Beta: 0.276; p < 0.05) and AIS was in independent relation with REM beta2 (Beta: 0.328; p < 0.05). We demonstrated for the first time in this population that the symptoms of depression and insomnia correlate with increased neurocognitive activity of the CNS during sleep, in particular, with increased NREM gamma and REM beta2 activity. These data support the hypothesis that CNS hyperarousal might contribute to the emergence of both conditions among kidney transplant recipients. Compared to routinely used sleep variables, quantitative analysis of EEG reveals further information about these conditions. The authors have no conflict of interest to declare in relation to this work.