Objective-to-Subjective Sleep Discrepancy in Patients with Rheumatoid Arthritis: A Pilot EEG Study

Background and Objectives: Sleep disturbance is common in patients with rheumatoid arthritis (RA), but the relationship between subjectively perceived and objectively measured sleep duration remains poorly understood. This pilot study aimed to compare objective and subjective total sleep time (TST) and to explore clinical factors associated with each measure and the difference between them. It also examined the relationship between this difference and nocturnal blood pressure regulation. Materials and Methods: Twenty-two hospitalized patients with RA underwent overnight sleep monitoring using a portable single-channel electroencephalography (EEG) device and provided subjective estimates of TST for the same night in response to a question asked the following morning. Sleep discrepancy was defined as subjective minus EEG-derived TST. Associations with clinical variables were assessed using Spearman’s rank correlation analysis with false discovery rate correction. Exploratory regression analyses adjusted for age, sex, and body mass index were performed. Ambulatory blood pressure monitoring was available for 20 patients. Results: Subjective TST exceeded EEG-derived TST by a median of 82.75 min (p = 0.0008), and the two measurements were not significantly correlated (ρ = 0.119, p = 0.598). A more positive signed sleep discrepancy was associated with lower serum albumin (ρ = −0.723, q = 0.0020), higher C-reactive protein (CRP) levels (ρ = 0.624, q = 0.0134), glucocorticoid use (q = 0.0462), higher DAS28-CRP (q = 0.0495), and greater functional disability (q = 0.0495). Associations with albumin and CRP persisted in separate exploratory models adjusted for age, sex, and body mass index. Patients with a conventional dipper blood pressure (BP) pattern had a lower signed sleep discrepancy than those with other nocturnal BP patterns (p = 0.0087). Conclusions: In this small exploratory study, subjective sleep duration in patients with RA was generally longer than EEG-derived sleep duration. Furthermore, preliminary associations were observed between sleep discrepancy and inflammatory and clinical characteristics, as well as with nocturnal BP patterns. These findings require confirmation in larger studies, and the clinical significance of sleep discrepancy remains uncertain.