Increased Aperiodic Neural Activity During Sleep in Major Depressive Disorder
Yevgenia Rosenblum, Leonore Bovy, Frederik D. Weber, Axel Steiger, Marcel Zeising, Martin Dresler
Abstract
In major depressive disorder (MDD), patients often express subjective sleep complaints while polysomnographic studies report only subtle alterations of the electroencephalographic (EEG) signal. We hypothesize that differentiating the signal into its oscillatory and aperiodic components may bring new insights into our understanding of sleep abnormalities in MDD. Specifically, we investigate aperiodic neural activity during sleep and its relationships with the sleep architecture, depression severity, and responsivity to antidepressant treatment. Polysomnography was recorded in 38 MDD patients (in unmedicated and 7-day medicated states) and 38 age-matched healthy controls (n=76). Aperiodic power component was calculated using the Irregularly Resampled Auto-Spectral Analysis. Depression severity was assessed with the Hamilton Depression Rating Scale. We replicated the analysis using two independently collected datasets of medicated patients and controls (n=60 and n=80). Unmedicated patients showed flatter aperiodic slopes compared to controls during non-REM 2 sleep (p=0.009). Medicated patients showed flatter aperiodic slopes compared to their later medicated state (p-values<0.001) and controls during all sleep stages (p-values<0.03). In medicated patients, flatter aperiodic slopes during non-REM sleep were linked to the higher proportion of non-REM 1, lower proportion of REM, delayed onset of non-REM-3 and REM, and shorter total sleep time. Flatter slopes of aperiodic EEG power may reflect noisier neural activity due to increased excitation-to-inhibition balance, representing a new disease-relevant feature of sleep in MDD.