Mood and motor activity in euthymic bipolar disorder with sleep disturbance

- A group of euthymic bipolar disorder patients show unstable rest-activity cycles.
- They also present more variability in mood and motor activity patterns.
- Patients with delayed sleep phase are potentially more affected.
- Mathematical analysis of actigraphy recordings produces a promising objective tool.

BackgroundThe aims of this observational study of patients with euthymic bipolar disorder and sleep disturbance were to 1) compare characteristics related to mood and sleep between two groups with stable and unstable rest-activity cycles and 2) detect between-group differences in motor activity patterns.Methods43 patients wore an actigraph for 6-8 days while reporting daily mood and sleep. Patients were defined as having an unstable rest-activity cycle if their diurnal active period duration presented variation above 2 h from the mean during one week: 22 patients had stable and 21 unstable rest-activity cycles. Mood variability was defined as at least moderate symptoms and a change across two levels on a 7-point mood scale during one week.ResultsPatients with unstable rest-activity cycles were younger (37 vs. 48 years, p=0.01) and displayed more mood variability (p=0.02). Ten of 11 patients diagnosed with delayed sleep phase disorder were in the unstable group (p<0.01), and the unstable group had later and more variable get-up-times and bedtimes. In actigraphy recordings, the mean activity counts per minute did not differ between groups, but the minute-to-minute variability was elevated (p=0.04) and increased relative to the overall variability (p=0.03).LimitationsA relatively small study sample and a 1-week study period prevent exploration of long-term clinical implications of results.ConclusionsA subgroup of euthymic patients with bipolar disorder displayed unstable rest-activity cycles combined with mood variability and motor activity patterns that resemble findings in affective episodes.