Sleep starts: Phenomenology and associations with sleep, psychological, and demographic characteristics

Sleep starts (SS) are transient phenomena during sleep onset. Although traditionally characterized by sudden muscle jerks, they may also involve sensory, cognitive, emotional, and autonomic experiences. Despite their high prevalence, empirical data on phenomenology and associated characteristics remain limited. This online survey examined SS phenomenology and exploratory associations with demographic, sleep-related, and psychological variables in 194 adults. Participants with self-reported sleep-related movement disorders or relevant medical conditions were excluded. Individuals reporting abrupt awakenings ≥1/week and ≥1 additional symptom formed the SS group (SS frequency ≥1, n = 96); all others the comparison group (SS frequency <1, n = 98). Because SS were operationalized using self-reported symptoms, they could not be distinguished from related sleep-onset phenomena (e.g., exploding head syndrome, hypnagogic hallucinations). Standardized questionnaires (PSQI, ISI, ESS, MZS, HADS) assessed sleep quality, insomnia severity, daytime sleepiness, dysfunctional sleep-related beliefs, and anxiety/depression symptoms. Participants described diverse experiences including motor jerks, falling sensations, dream-like experiences, somatosensory symptoms, autonomic arousal, and emotional reactions, accompanied by alarm, anxiety, and confusion. Compared with controls, the SS group reported poorer sleep quality, greater insomnia severity, stronger dysfunctional sleep-related beliefs, and higher anxiety/depressive symptoms (all p < .05). Exploratory regression analyses indicated that poorer sleep quality, stronger dysfunctional sleep-related beliefs, and higher anxiety symptoms were associated with higher SS frequency, whereas depressive symptoms were not. The final model explained 26.9% of variance (R 2 = .269, adjusted R 2 = .245). More frequent SS were retrospectively reported during emotional stress, whereas sleep deprivation was perceived as less influential. Although many described SS as manageable, a substantial subgroup reported distress and sleep disruption. This suggests that SS represent heterogeneous sleep-onset experiences associated with subjective sleep disturbance and cognitive-emotional arousal. Although causality cannot be inferred from cross-sectional self-report data, the results highlight potentially relevant links between SS and sleep-related cognitive-emotional processes.