Dissociated sleep states in fibromyalgia: Prevalence and correlations

Abstract

Introduction One of the prominent features in fibromyalgia patients (FMP) is the discrepancy between subjective and objective data. Pain index are more intense than in Rheumatoid Arthritis patients but supportive objective data are lacking. Sleep is among the most prevalent complaints and the intrusion of alpha activity, although common, is not specific. It may be considered that, somehow, the peripheral dysfunctions or complaints are magnified centrally. Therefore the objectives are: 1) To compare sleep and sleep questionnaires in FMP and healthy controls (HC); 2) To identify dissociated states (DS) in sleep microstructure,i.e., occurrence of alpha delta, NREM microevents in REM, presence of REMs and myoclonia in NREM. Materials and methods 20 FMP, mean age 44.00, and 14 HC, mean age 43.21, all females were evaluated with the following instruments: Type 1 PSG with 19 EEG electrodes, PSQI and Epworth Sleepiness scale (ESS). PSG were visually staged by experienced technicians and dissociated states were scored by a single technician. The percentage of DS (taking as reference the total number of sleep epochs per subject) was computed together with current sleep parameters. Student T test was used to evaluate differences between groups and Pearson correlation analysis was done to evaluated correlations between individual measures. Results Significant differences between groups are: Body Mass Index (FMP = 25.68; HC = 22.58); PSQI (FMP = 11.8; HC = 5.23); %N1 (FMP = 13.0; HC = 6.3); Microarousals (FMP = 37.8; HC = 40.4); Periodic Limb Movements of Sleep (PLMS) (FMP = 2.8; HC=.73); Alpha delta (AD) (FMP = 21.0; HC = 7.9); NREM myoclonia (FMP=.02; HC = 0.0); absence of DS (FMP = 76.8; HC = 90.6). Correlation analysis provided the following results: A- Sleep parameters: Total Sleep Time (TST) correlated with Time in bed (TIB), Sleep efficiency (SE), %N2, and negatively with %N3. SE correlates negatively with Sleep Latency (SL), REM latency (RL), %N1, Awakenings SL correlates with TIB, RL, %N1 RL correlates with TIB, Awakenings, PLMS, PSQI and negatively with %R %N1 correlates with Awakenings, PLMS, PSQI and negatively with %N3, % R %N2 correlates negatively with %N3, % R, ESS %N3 correlates with Awakenings, PSQI, ESS %R correlates negatively with Awakenings Apnea-Hypopnea Index (AHI) correlates with age PLMS correlates with PSQI ESS correlates with %N3 and negatively with %N2 B- DS parameters: AD correlates with Awakenings, %N2, Alpha REM (AR), REMs in NREM, REM without atonia and negatively with %R, ESS, absence of DS AR correlates with K-complex in REM and negatively with absence of DS Spindles in REM correlates with RL, Microarousals and NREM myoclonia REMs in NREM correlates with %N1, Awakenings, REM without atonia and negatively with ESS, absence of DS Microarousals correlates with NREM myoclonia NREM myoclonia correlates with Microarousals, PSQI, ESS REM without atonia correlates with RL, % N2, AD and negatively with %R, absence of DS Absence of DS correlates with %R, ESS and negatively with awakenings 1421. Conclusion Concerning our objectives it must be stated that the differences between groups are not overwhelming; the existent in term of polisomnography are mostly related with sleep microstructure. In fact FMP have decreased Microarousals, higher PLMS index and percentage of DS comparing with HC. FMP have also higher percentage of alpha delta sleep and NREM Myoclonia. In spite of this, and in line with the dissociation hypothesis, the subjective complaints evaluated by the PSQI are higher in FMP. The presence of dissociated states in sleep EEG is a further proof in favor of this hypothesis. The correlations found are in line with the general postulates of sleep organization. Acknowledgements Funded by: FCT project ”‘Detection of Brain Microstates in Fibromyalgia”’ (PTDC/SAU-BEB/104948/2008) Work supported by the technicians Joana Belo and Patricia Correia.