Circadian rest-activity rhythm and sleep in women with fibromyalgia and other central sensitization syndromes

Objective To investigate circadian rest-activity rhythms (RAR) in women with fibromyalgia and other central sensitization syndromes (CSS) and examine links with symptom severity. Methods Cross-sectional study including 73 women with fibromyalgia, 40 women with CSS, and 33 controls. Participants completed seven nights of actigraphy and sleep diaries. Sleep and nonparametric RAR parameters were derived, including least-active five-hour period (L5), most-active ten-hour period (M10), relative amplitude (RA), interdaily stability (IS), and intradaily variability (IV). Pain, fatigue, functional impact, anxiety, depression, and sleep quality were assessed with questionnaires. Analyses included age-adjusted analysis of covariance and partial correlations. Results Both patient groups showed reduced daytime activation versus controls (lower M10 activity). Fibromyalgia participants exhibited later onset of the least-active period (L5 onset) and greater IV, indicating fragmented rhythms. CSS participants demonstrated higher nocturnal activity (L5 average) and greater sleep fragmentation than fibromyalgia and controls, respectively. Syndrome-specific associations emerged: in CSS, earlier M10 onset and higher sleep fragmentation were associated with poorer subjective sleep quality. In fibromyalgia, higher IV was associated with greater reported fatigue. Conclusion Women with fibromyalgia and other CSS shared lower daytime activation but diverged in 24-h disruption: fibromyalgia by within-day fragmentation and later least-active timing, other CSS by nocturnal activation and sleep-maintenance disturbance. These syndrome-specific patterns suggest exploring condition-specific rather than uniform management approaches.