Ultradian Sleep Cycles Correlate With REM Alterations in Major Depression

Alterations in rapid eye movement (REM) sleep architecture may be associated with the number of sleep ultradian cycles in patients with major depressive disorder (MDD), according to study data published in Psychiatry Research. Higher numbers of sleep ultradian cycles were correlated with REM sleep (REMS) disinhibition, whereas lower numbers correlated with REMS deficiency. 

Investigators at the department of psychiatry and sleep laboratory, Erasme Hospital in Brussels, Belgium abstracted data from 3511 individuals who underwent sleep examinations between 2002 and 2014. They examined medical records data for 211 people (181 with untreated MDD; 30 healthy controls). Patients with a major sleep disorder other than hypersomnia or insomnia secondary to depression were excluded, and patients with MDD were not receiving psychotropic medication at the time of examination.

From the polysomnographic recordings, the investigators calculated the number of sleep ultradian cycles, defined as the combination of a REMS episode and the immediately preceding non-REMS (NREMS) episode. REMS episodes had no minimum duration, though ultradian cycles required at least 15 minutes of NREMS to be recorded. The number of sleep ultradian cycles were dichotomized (>4 vs <4 cycles), and sleep data from healthy controls were used as baseline parameters. The investigators also measured depression symptoms, insomnia, and excessive daytime sleepiness.

Patients with MDD who had <4 sleep ultradian cycles (n=61) demonstrated sleep alteration indicative of REMS deficiency compared with controls, including a decrease in REMS percentage, REMS duration, and REMS/NREMS ratio (all P <.001). In contrast, patients with depression who had >4 ultradian sleep cycles (n=52) displayed sleep alterations consistent with REMS disinhibition, including shortened REM latency and increases in REMS percentage, REMS duration, and REMS/NREMS ratio (all P <.001). Among patients with MDD and exactly 4 sleep ultradian cycles, REMS alterations were observed at a severity between that of patients with <4 and >4 cycles.

Overall, in all patients with MDD, sleep ultradian cycle number was positively associated with REMS percentage, REMS duration, and REMS/NREMS ratio and negatively associated with REM latency (all P <.05). As study limitations, however, the investigators cited the retrospective design and the potentially limited external generalizability.

Overall, the investigators concluded that REM alterations support the “involvement of distinct pathophysiological mechanisms” in MDD. Specifically, MDD subtypes characterized by REMS alterations appear to correlate with the number of sleep ultradian cycles, and heterogeneity in REMS alterations could provide a roadmap for future sleep-based research in depression.

Reference

Hein M, Lanquart JP, Mungo A, Hubain P, Loas G. Impact of number of sleep ultradian cycles on polysomnographic parameters related to REM sleep in major depression: implications for future sleep research in psychiatry [published online January 26, 2020]. Psychiatry Res. doi: 10.1016/j.psychres.2020.112818