An actigraphy study investigating sleep in bipolar I patients, unaffected siblings and controls

•We found no sleep disturbances in bipolar patients and non-affected siblings compared to controls.•We found no relation between sleep pattern and bipolar illness characteristics.•Measures of depression and sleep pattern were directly associated in patients.•Our data suggests that sleep disturbances are primarily a state marker of mood symptomatology.

ObjectivesDisturbances in sleep and waking patterns are highly prevalent during mood episodes in bipolar disorder. The question remains whether these disturbances persist during phases of euthymia and whether they are heritable traits of bipolar disorder. The current study investigates objective sleep measures in a large sample of bipolar I patients, non-affected siblings and controls.MethodsA total of 107 bipolar disorder I patients, 74 non-affected siblings, and 80 controls were included. Sleep was measured with actigraphy over the course of 14 days. Seven sleep parameters were analyzed for group differences and their relationship with age at onset, number of episodes and psychotic symptoms using linear mixed model analysis to account for family dependencies.ResultsPatients had a longer sleep duration and later time of sleep offset compared to the non-affected siblings but these differences were entirely attributable to differences in mood symptoms. We found no difference between patients and controls or siblings and controls when the analyses were restricted to euthymic patients. None of the bipolar illness characteristics were associated with sleep.LimitationsMedication use was not taken into account which may have influenced our findings and controls were younger compared to non-affected siblings.ConclusionsIn the largest study to date, our findings suggest that recovered bipolar I patients and their siblings do not experience clinically significant sleep disturbances. Sleep disturbances are primarily a reflection of current mood state, but are unrelated to the course of the disorder.