Comparison of subjective and objective measures of insomnia in monozygotic twins discordant for chronic fatigue syndrome

Study Objectives: To examine the objective and subjective measures of insomnia in chronic fatigue syndrome (CFS). Design: Monozygotic co-twin control study. Setting: Academic medical center. Patients or Participants: Twenty-two pairs of monozygotic twins where 1 member of the pair had CFS and the other did not. Interventions: N/A Measurements and Results: Twenty-two CFS-discordant twin pairs completed a Sleep Disorders Questionnaire, overnight polysomnography, and a postpolysomnography sleep survey. Mean and percent differences in the sleep measures were compared between the CFS and healthy twins using matched-pair methods of analysis. Compared with their healthy co-twins, the CFS twins more frequently endorsed 8 subjective measures of insomnia and poor sleep (all p less than or equal to 0.05). However, the CFS and healthy twins did not differ in objective polysomnographic measures of insomnia, including sleep latency, total sleep time, sleep efficiency, arousal number, arousal index, hypnogram awakenings, rapid eye movement (REM)-sleep latency, and percent stages 1, 2, and 3-4 (delta). Percent stage REM sleep was increased in the CFS twins compared with the healthy twins (27.7% vs. 24.4%, p less than or equal to 0.05). On the postpolysomnography survey, CFS twins reported that they had slept fewer hours (6.2 vs. 6.7; p less than or equal to 0.05), and were less well rested (p less than or equal to 0.001) compared to their co-twins. Conclusions: CFS patients had worse subjective sleep than their cot-wins despite little objective data supporting this discrepancy, suggesting they suffer from an element of sleep-state misperception. The higher percentage of REM sleep in the CFS twins implies that REM sleep may play a role in this illness.