MIAMI BEACH – Patients with active bipolar disorder significantly underestimated the quality of their sleep, despite having sleep quality comparable to that of healthy controls.
Sleep complaints are common among individuals with bipolar disorder, and addressing disruptive and troubling sleep problems can be an important component of treating bipolar disorder, noted Dr. Venkatesh Krishnamurthy and his collaborators at Penn State University (Hershey, Pa.).
“Mood state may affect perception of sleep, and the impact of mood state on subjective-objective differences of sleep parameters needs to be further explored,” the researchers noted.
They reported their comparison of subjective and objective measures of sleep for symptomatic patients with bipolar disorder in a poster presentation at a meeting of the American Society for Clinical Psychopharmacology, formerly known as the New Clinical Drug Evaluation Unit meeting.
The study researchers evaluated 30 individuals with symptomatic bipolar disorder, compared with 31 healthy controls, reported Dr. Krishnamurthy, assistant professor at the department of psychiatry’s Sleep Research and Treatment Center at Penn State’s Milton S. Hershey Medical Center. Patients with bipolar disorder were inpatients or in a partial hospitalization program; 11 patients had bipolar depression, 18 had mixed-state bipolar disorder, and 1 had bipolar disorder with a manic episode, Dr. Krishnamurthy said in an interview.
To compare subjective and objective measures of sleep in the two groups, the researchers administered a sleep-quality questionnaire and used actigraphy to document sleep objectively.
The Pittsburgh Sleep Quality Index (PSQI), the instrument used for subjective assessment, is a self-reporting tool that asks patients to report on aspects of sleep quality, usual sleep duration, daytime sleepiness, and sleep medication use over the past month.
The actigraphs used in the study used accelerometers to measure patient movement at a per-second level, and were worn around the clock for the week of the study. These devices, said Dr. Krishnamurthy, give sleep data that correlate well with polysomnography, the gold standard for sleep assessment.
For both patient groups, Dr. Krishnamurthy and his colleagues reported sleep latency, sleep duration, sleep dysfunction, sleep efficiency in percentage, sleep quality, and medication need as assessed by the PSQI, as well as the overall PSQI score.
The group with bipolar disorder reported a mean time to falling asleep of 61 minutes, compared with 14 minutes for the control group (P = 0.00064). Total sleep duration from the PSQI was 6.2 hours in the bipolar disorder patients, compared with 7.4 hours in the control group (P = 0.017). All other subjective measures of sleep quality were significantly worse for the patients with bipolar disorder, and the overall score on the PSQI was also much higher (worse), compared with the control group (11.7 vs 3.3, P = 1 x 10-11).
Actigraphy was used for a 1-week period to measure sleep latency, total sleep time, sleep efficiency, and number and length of awakenings for both groups. When measured objectively, there was no significant difference in the time it took to fall asleep between the patients with bipolar disorder and the healthy controls (14.64 minutes vs. 13.15 minutes), nor was there a significant difference in total sleep time (400.7 minutes vs. 413 minutes). Overall sleep efficiency was similar between groups.
The absolute difference in sleep duration, latency, and efficiency between subjective and objective measures was compared between groups. There was significantly less difference between objective and subjective ratings of all three sleep measures in the healthy subjects than in those with bipolar disorder.
Overall, the patients with bipolar disorder exhibited a strong perception of poor sleep quality, daytime impairment, and insufficient sleep, as shown by the PSQI scores for this group in comparison with the healthy controls. However, these perceptions did not correlate with objective sleep measures for sleep latency, total sleep duration, or sleep efficiency.
Patients with bipolar disorder were significantly more likely to lack employment and to be smokers or use illicit substances; their body mass index was also significantly higher on average than their healthy counterparts.
The bipolar disorder patients may have altered circadian rhythms, cognitive dysfunction because of the illness, and dysfunctional sleep beliefs, which may have independent effects on subjective perceptions of sleep that were not accounted for in the study, said Dr. Krishnamurthy.
The study’s findings mean that clinicians may wish to consider incorporating objective assessments of sleep, such as actigraphy, into care of individuals with bipolar disorder and sleep disturbances, Dr. Krishnamurthy said in an interview. In addition, “behavioral methods to address sleep misperception may be helpful in bipolar subjects.”
The Penn State Hershey College of Medicine funded the study. The authors reported no relevant disclosures.