Significant sleep disturbances in euthymic bipolar patients

Objective

A growing amount of data suggests that sleep dysfunction is frequently observed in bipolar disorder (BD) patients even when they do not fulfill the criteria for major mood episodes. Thus, we performed a case–control study assessing sleep status in a group of euthymic BD patients and a group of health controls.

Methods

A total of 209 subjects (104 health controls and 105 BD patients) were enrolled in the study. The Pittsburgh Sleep Quality Index (PSQI) was used for sleep assessment. Inclusion criteria for the BD group were a diagnosis of BD, following DSM-IV-TR criteria, according to the MINI-plus structured clinical interview. Euthymia was established as a score lower than 7 both in the Hamilton Depression Rating Scale (HDRS) and in the Young Mania Rating Scale (YMRS). Health controls were also interviewed using the MINI-plus and included in this study if they were free of any current or past DSM-IV-TR axis I psychiatric disorder as well the actual use of psychopharmacological medications.

Results

While 21.2 % of the control group displayed poor sleep quality according to the global PSQI-BR score, 82.9 % of the euthymic BD patients had poor sleep quality (p = 0.000). PSQI sleep duration subcomponent showed comparable results in the two groups (p = 0.535), even though BD patients had significant disruptions in sleep latency (p = 0.000) and sleep efficiency (p = 0.000) subcomponents.

Conclusion

We were able to show that BD patients, even in euthymic phase, exhibit a significantly worse sleep quality as compared with health controls as assessed by PSQI total score and five of its seven subcomponents.