Background <p>Patients with primary headache disorders including migraine and cluster headache often report poor sleep quality. While subjective reports of disturbed sleep are well established, the objective alterations in sleep architecture which occur in primary headache have not been systematically characterised. This systematic review aims to determine whether previously identified macrostructure changes in migraine occur across trigeminal autonomic cephalalgias, how sleep microstructure is altered, and how sleep architecture differs between the headache-free and headache attack phase.</p> Methods <p>We conducted a systematic review across four databases (Embase, Medline, PubMed and APA PsycInfo) to identify studies assessing objective sleep parameters via polysomnography or actigraphy in individuals with migraine or cluster headache, including relevant animal models of migraine-related pain. Thirty studies met the inclusion criteria and were critically appraised in a narrative synthesis with respect to sleep macrostructure (including NREM-REM architecture, sleep fragmentation, sleep duration and sleep efficiency metrics), and sleep microstructure (cyclic alternating pattern and arousal indices).</p> Findings <p>Significant heterogeneity across studies was observed resulting in varied findings. In adult migraine patients, 50% of included studies reported a significant reduction in sleep efficiency, while an increase in the number of awakenings was identified in the majority of studies reporting this metric, highlighting potential sleep fragmentation. Assessment of sleep microstructure identified altered arousal profiles, though no clear pattern of hypo- or hyper-arousal emerged. These arousal profiles were also found to differ across different phases of the headache attack, with a small number of studies identifying a reduction in arousal the night preceding migraine headache attack. Studies assessing sleep in cluster headache were less common, although some evidence indicates alterations to REM sleep architecture, consistent with previous findings in migraine. Sleep efficiency and sleep onset latency alterations further indicate sleep disruption however further replication is required to gain a broader understanding of how sleep is altered both in bout and in remission.</p> Conclusion <p>Objective assessment supports disrupted sleep in headache disorders, with some evidence of altered sleep fragmentation and microstructure. Further studies focusing on these less widely reported metrics are necessary for a full understanding of sleep in migraine and cluster headache.</p>