Atlas and Updated Rules for the Scoring of Cyclic Alternating Pattern ( <scp>CAP</scp> ) in Human Sleep. A Consensus Report by a Taskforce of the European Sleep Research Society

The cyclic alternating pattern is a hallmark of the dynamic organisation of non-rapid eye movement sleep, reflecting the brain's oscillatory regulation of arousal and sleep stability. Since the original publication of the rules for scoring the cyclic alternating pattern in 2001, major advances in sleep neurophysiology, signal analysis and international sleep staging standards have necessitated a comprehensive revision. This consensus report by a Taskforce of the European Sleep Research Society presents the updated 2025 Atlas and Rules for the scoring of the cyclic alternating pattern in human sleep. The new guidelines preserve the foundational framework of the cyclic alternating pattern while introducing several critical innovations: (i) expanded definitions and a broader catalogue of Phase A electroencephalographic patterns; (ii) refined onset and offset criteria based on amplitude and frequency shifts, with strict inter-lead concordance requirements; (iii) standardised metrics for the quantification and reporting of the cyclic alternating pattern; (iv) formal guidance for scoring the cyclic alternating pattern in paediatric populations and optional scoring in rapid eye movement sleep; and (v) a technical framework for computerised detection and analysis. These updates align scoring with contemporary sleep staging standards, enhancing precision, reproducibility and applicability across research and clinical contexts.