Sleep disturbance between episodes of bipolar disorder can affect illness course and may therefore be an important intervention target, say researchers.

“While several psychologic therapies for bipolar disorder target sleep disturbance, there remains significant room for improvement in treatment outcome and a need for basing treatments in empirical research,” say Allison Harvey and colleagues from the University of California in Berkley, USA.

The researchers enrolled 21 participants aged an average of 37 years with bipolar disorder who were inter-episode and asked them to complete sleep diaries for a week. Illness course and symptoms were assessed via validated semi-structured interviews.

Average total wake time ranged from 12.83 to 193.00 minutes, while average total sleep time ranged from 264.67 to 546.86 minutes and average sleep efficiency ranged from 61% to 96%.

The findings, published in the Journal of Behavior Therapy and Experimental Psychiatry, showed that participants experiencing a greater number of depressive episodes had significantly poorer and more variable sleep efficiency and more variable total wake time than other patients.

A greater number of depressive episodes also correlated, albeit not significantly, with more variability in the time at which they went to bed.

“It may be the case that experiencing a greater number of depressive episodes, which are marked by disturbed sleep, leads to spending more time in bed than is spent sleeping, possibly as the bed comes to be associated with poor sleep and depression,” suggest the researchers.

“Alternately, spending excessive time awake in bed may have detrimental effects on mood.”

The researchers also found that sleep efficiency correlated positively with concurrent manic symptoms, and although not statistically significant, there was a negative correlation between total wake time and manic symptoms other than sleep disturbance.

“This is surprising because sleep efficiency is typically considered to be a sign of good sleep,” note Harvey and team.

“These findings raise the possibility that experiencing more manic symptoms may be associated with a greater likelihood of leaving the bed during awakenings in the night or getting up earlier in the morning and starting the day rather than attempting to return to sleep.”

The researchers conclude: “Our findings support the theory that sleep disturbance may be a potential trait marker of bipolar disorder, and they extend previous research by raising the importance of sleep efficiency and sleep variability as critical sleep parameters in bipolar disorder.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

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