Polysomnographic characteristics of bipolar hypomanic patients: Comparison with unipolar depressed patients

- Sleep efficiency was reduced and sleep latency was prolonged in both case groups.
- Depressed patients had remarkable decrease in sleep efficiency, stage III-IV percentage as compared to hypomanic patients.
- Depressed patients had reduced REM latency and increased REM percentages and REM density as compared to hypomanic patients. NREM sleep: increase in stage I and II with reduction in SWS in cases group.
- REM sleep: significant elevation in REM density and percentage and reduced REM latency in both case groups.
- REM sleep percentage was higher in MDD compared to controls, and did not differ significantly in hypomania compared to controls.
- There was higher polysomnographic values for sleep efficiency and slow wave sleep in hypomanic patients in comparison to depressed patients.
- Polysomnographic findings for hypomanic patients were nearly similar to that found in depressed patients, but these finding values were in the middle range between the depressed patients and healthy controls.
- The observed similarities in PSG findings between MDD and BD are consistent with the suggestion that a common mechanism underlies the sleep disturbance in both disorders.
- The relative decrease of sleep efficiency and SWS in depressed patients in comparison to hypomanic group, suggests that the differences are more of quantitative nature rather than qualitative.

BackgroundSleep profile in bipolar disorder has received little attention in comparison to sleep studies in major depressive disorders. Specific sleep abnormalities especially in REM sleep parameters have been detected in depression. The current study aimed at investigating whether bipolar disorder shares the same polysomnographic (PSG) changes or not.MethodsAll night polysomnographic assessments were made for 20 patients diagnosed to have hypomania, in addition to 20 patients with major depression and 20 healthy matched controls. All participants were examined using Standardized Sleep Questionnaire, SCID-I for psychiatric diagnosis, based on DSM-IV criteria, YMRS (for hypomanic patients), HAMD (for major depression patients), and all-night polysomnography (for all subjects).ResultsThe two patient groups differed significantly from controls in their sleep profile, especially regarding sleep continuity measures, Short REML (Rapid Eye Movement Latency), with increased REMD (Rapid Eye Movement sleep density). High similarity was found in EEG sleep profile of the two patient groups, though the changes were more robust in patients with depressionLimitationsA relatively small sample size, the absence of follow up assessment, lack of consideration of other variables like body mass index, nicotine and caffeine intake.ConclusionSimilarity in EEG sleep profile between Bipolar disorder patients and patients with major depression suggests a common biological origin for both conditions, with the difference being “quantitative” rather than “qualitative”. This quantitative difference in sleep efficiency and SWS (Slow wave sleep), being higher in hypomania, might explain the rather “refreshing” nature of sleep in hypomanic patients, compared to depression.