Bipolar disorder severity worsened by poor sleep quality
MedWire News: Sleep quality may play a role in the course of bipolar disorder, with shorter total sleep time (TST) and increased sleep variability (SV) both associated with symptom severity, conclude a team of US researchers.
Previous studies have indicated that bipolar disorder patients have a reduced need for sleep during manic episodes, and either insomnia or hypersomnia during depressive episodes. Furthermore, 70% of euthymic patients have clinically significant levels of sleep disturbance.
To determine the possible role of sleep quality in bipolar disorder, June Gruber, from Yale University in New Haven, Connecticut, and colleagues examined baseline TST and SV data, along with symptom severity and functioning, in 468 bipolar disorder patients taking part in the National Institute of Mental Health Systematic Treatment Enhancement Program for Bipolar Disorder. Follow-up data was also available for 196 patients.
At baseline, age was weakly but significantly negatively correlated with TST, which was also negatively correlated with illness duration and age at onset, indicating that patients with an earlier age at onset and a longer illness duration slept less well and more variably.
Lower TST was significantly associated with increased mania severity scores, while greater SV was significantly associated with increased mania and depression severity scores. There was no significant association between either sleep marker and global functioning.
Consistent with these findings, the researchers reports in the Journal of Affective Disorders that, at 12 months, shorter TST was linked to increased mania severity, while increased SV was linked to increased mania and depression severity.
They conclude: "The present findings represent an important initial step towards identifying aspects of sleep functioning that may contribute to clinical impairment in bipolar disorder.
"Furthermore, this research underscores the importance of incorporating interventions that target sleep functioning aimed at promoting illness stabilization."
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By Liam Davenport