Effects of Subjective and Objective Sleep Measures on Diurnal Variation in Pain Intensity Among Patients With Chronic Pain: Implications for Time‐of‐Day–Dependent Pain Management

OBJECTIVE: This study aimed to examine the effects of subjective insomnia severity and objective sleep efficiency (SE) on diurnal variation in pain intensity among patients with chronic pain. METHODS: Forty-four community-dwelling patients with chronic pain lasting more than three months were enrolled. Pain intensity was recorded using a visual analog scale at six time points per day over three consecutive days. Subjective sleep was assessed once using the Athens Insomnia Scale (AIS), and objective SE was derived from three days of actigraphy recordings. Linear mixed-effects models included pain intensity as the dependent variable; AIS score, sleep efficiency, time of day, and their interactions as fixed effects, as well as participant ID as a random effect. RESULTS: Significant main effects of time (F = 4.84, p < 0.001) and the AIS score (F = 7.58, p = 0.009) were observed. Significant interactions were found between SE and time of day (F = 3.64, p = 0.003), as well as between the AIS score and time of day (F = 2.55, p = 0.027). Higher AIS scores were associated with greater pain intensity, particularly in the morning. Higher SE was associated with higher pain intensity upon waking but lower pain intensity in the evening. CONCLUSION: In this exploratory study, subjective insomnia severity showed a consistent association with diurnal variation in pain intensity, whereas SE was associated with pain intensity in a time-of-day-dependent manner. These findings, which should be interpreted as hypothesis-generating rather than definitive, suggest that subjective and objective sleep measures capture distinct aspects of time-of-day-dependent pain variation and may inform individualized approaches to pain management, including patient education and rehabilitation planning.