Clinical, sleep-related and polysomnographic features of dyssomnic disorders in chronic nonspecific low back pain

Introduction. Chronic nonspecific low back pain (CNLBP) is often accompanied by dyssomnic disorders, but the relationship between subjective sleep complaints, psychometric characteristics, and objective sleep measures remains insufficiently studied. Objective. To describe the clinical spectrum of dyssomnic disorders and their psychometric and polysomnographic features in patients with CNLBP. Materials and methods. This cross-sectional comparative study included baseline data from 143 patients aged 31-60 with CNLBP: 100 patients with clinically significant dyssomnic disorders and 43 patients without clinically significant sleep disturbances. All study participants underwent clinical and neurological examination, pain and disability assessment, assessment of subjective sleep characteristics, daytime sleepiness, psychological well-being, anxiety and depressive symptoms, assessment of symptoms associated with central sensitization, and overnight polysomnography. Between-group differences were analyzed with the Mann-Whitney U test and Fisher’s exact test. Correlations within the dyssomnia group were assessed using Spearman’s rank correlation coefficient. Results. Sleep-maintenance (intrasomnic) disturbances were the most common variant (52.0%); sleep-onset (presomnic) and early-morning awakening (postsomnic) variants were found in 25.0% and 23.0% of patients, respectively. Pain intensity was higher in patients with dyssomnic disorders than in the comparison group: 7.0 [6.0; 8.0] versus 6.0 [5.0; 7.0] points (p<0.001), whereas Oswestry Disability Index and Roland-Morris Disability Questionnaire scores did not differ. Patients with dyssomnic disorders (the main group) had significantly worse PSQI, ESS, PGWB, HADS, HARS, BDI, and Central Sensitization Inventory scores (all p<0.001). Polysomnography showed shorter total sleep time – 327.5 [315.8; 348.3] versus 365.0 [356.0; 444.5] min, lower sleep efficiency – 76.0 [72.0; 79.3] versus 86.0 [86.0; 89.5]%, increased wake after sleep onset (WASO) – 59.0 [49.0; 69.0] versus 24.0 [20.0; 28.0] min, increased N1 sleep, reduced N3 and REM sleep, and a higher EEG arousal index (for all the mentioned comparisons p<0.001). In the comparison group, 23 of 43 patients (53.5%) showed isolated abnormalities in sleep-onset or sleep-maintenance parameters without clinically significant sleep complaints or daytime impairment. The strongest correlations were observed between the subjective sleep characteristics questionnaire and PSQI (r_s=-0.874), WASO and REM sleep percentage (r_s=-0.731), Oswestry Disability Index and sleep efficiency (r_s=-0.587), and Roland-Morris Disability Questionnaire score and sleep efficiency (r_s=-0.561); p<0.001. Conclusions. In patients with CNLBP, dyssomnia most often manifested as sleep-maintenance disturbance and was associated with objective sleep fragmentation, reduced N3 and REM sleep, greater pain intensity, more pronounced anxiety and depressive symptoms, and higher scores for symptoms associated with central sensitization. The marked sleep-related and psychometric differences, despite similar disability scores, show that clinical assessment of CNLBP should extend beyond pain intensity and disability. Isolated polysomnographic abnormalities in patients without clinically significant dyssomnia may reflect subclinical sleep disruption; their prognostic relevance requires prospective follow-up.