Temporal Associations Between Physiological Sleep and Next‐Day Pain Intensity in Individuals With Activity‐Limiting Chronic Pain: A Multiple Night At‐Home Ear‐ EEG Sleep‐Monitoring Study

ABSTRACT

Chronic pain and sleep disturbances frequently co‐occur. However, most prior research relies on self‐report or actigraphy, which reflect behavioural aspects of sleep but provide only limited insight into the underlying sleep physiology. In this pre‐registered prospective observational study (NCT06368531), we investigated within‐person night‐to‐night variability in physiological sleep metrics and explored temporal associations between sleep metrics and next‐day pain. Individuals with bothersome ( n  = 4) or high‐impact ( n  = 15) chronic pain completed between 11 and 33 nights of at‐home sleep monitoring using an ear‐EEG device and rated morning pain intensity daily on a 0–10 numerical rating scale. This design enables assessment of real‐world physiological sleep patterns alongside natural fluctuations in pain, offering a high‐resolution view of sleep–pain dynamics beyond traditional diary or actigraphy‐based methods. Substantial between‐night variability was observed across multiple sleep metrics, such as sleep efficiency and sleep stage transitions (ICC values < 0.5), indicating that less than half of the total variance was attributable to differences between subjects, underscoring the importance of longitudinal within‐person monitoring. Mixed‐effects model analyses revealed that lower next‐day pain intensity was associated with greater duration ( β  = −0.01, p  = 0.005), higher percentage ( β  = −0.07, p  = 0.001) and increased stability ( β  = −0.01, p  = 0.013) of N3 sleep. In contrast, higher next‐day pain was associated with increased N3 fragmentation ( β  = 0.01, p  = 0.014) and a higher proportion of N1 sleep ( β  = 0.014, p  = 0.007). Together, these findings provide objective physiological support for previously reported associations between sleep and pain, highlighting the value of longitudinal ear‐EEG monitoring for capturing nightly sleep–pain dynamics.

Trial Registration: ClinicalTrials.gov identifier: NCT06368531.