Sleep disruptions represent a core feature of bipolar disorders and have been widely studied through the use of actigraphy, which is an objective measure of motor activity and sleep. Finding objective outcomes, which reliably measure sleep in bipolar disorders, is essential in developing better therapies and improving follow-up monitoring strategies. Our aim is to understand the role of actigraphy as an objective measure of sleep in bipolar disorder. We undertook a systematic review and meta-analysis on studies using actigraphy to detect changes in activity and sleep patterns in bipolar patients versus healthy controls. The primary outcome measures were the analyses of 'activity mean' and 'sleep duration'. As secondary outcomes we analysed 'sleep onset latency', 'sleep efficiency', and 'time awake after sleep onset'. Thirteen studies comprising 821 subjects met quality criteria for inclusion. The results show a decrease in activity mean and an altered pattern of sleep in bipolar patients. Further analyses suggest that the results might be generalized to a bipolar condition which underlies manic and depressed episodes as well as euthymic phases. This study highlights the role of actigraphy as an important objective tool for the ambulatory monitoring of sleep and activity in bipolar disorders. (C) 2016 Elsevier Ltd. All rights reserved.