The cyclic alternating pattern demonstrates increased sleep instability and correlates with fatigue and sleepiness in adults with upper airway resistance syndrome.

OBJECTIVE: To clarify the relationship between sleep instability and subjective complaints in patients with upper airway resistance syndrome (UARS).
METHODS: Thirty subjects (15 women) with UARS and 30 age- and sex-matched controls in a prospective, single-blind, case-control study. Blinded cyclic alternating pattern (CAP) electroencephalogram analysis and scales of fatigue and sleepiness were completed. ANALYSIS: Mann-Whitney U tests for independent, nonparametric variables between groups and chi2 tests for nonparametric variables with defined standard values.
RESULTS: Patients with UARS had significantly more complaints of fatigue and sleepiness, compared with controls, demonstrated on their Fatigue Severity Scale (P < 0.001) and Epworth Sleepiness Scale (P < 0.001). By design, the mean apnea-hypopnea index was normal in both groups, whereas the respiratory disturbance index was greater in patients with UARS than in those without (14.5 +/- 3.0 vs 9 +/- 5.2, respectively [P < 0.001]). CAP analysis demonstrated abnormal non-rapid eye movement sleep with abnormally increased CAP rate, electroencephalogram arousals, A2 index, and A3 index. Decreased A1 index in controls was consistent with their more normal progression of sleep. CAP rate correlated with both the Epworth Sleepiness Scale (r = 0.38, P < 0.01) and the Fatigue Severity Scale (r = 0.51, P < 0.0001), and there was a positive trend between the Fatigue Severity Scale and phase A2 index (r = 0.29, P < 0.05).
CONCLUSION: Compared with age- and sex-matched controls, patients with UARS have higher electroencephalogram arousal indexes and important non-rapid eye movement sleep disturbances that correlate with subjective symptoms of sleepiness and fatigue. These disturbances are identifiable with sensitive measures such as CAP analysis but not with traditional diagnostic scoring systems.