Arousals in nocturnal groaning

Background and objectiveNocturnal groaning (catathrenia) is a chronic sleep disorder classified as parasomnia with unclear effects on sleep and life quality. It is characterized by repeated episodes of monotonous vocalization in prolonged expiration (episodes of bradypnea) occurring mostly in REM sleep. We sought to assess its impact on sleep microstructure, i.e., the frequency of arousals relative to the groaning episodes. The frequency, duration and sleep-stage distribution of the groaning episodes were also studied.MethodsEight patients with nocturnal groaning (5 male, 3 female, age range 11–32 years, mean age 23 ± 7.1) were evaluated. All underwent standard neurologic examination and nocturnal videopolysomnography for two consecutive nights. The second night polysomnography data were used to evaluate sleep parameters. The groaning episodes (bradypneic events) were counted separately, not as clusters.ResultsSleep macrostructure revealed no specific changes. The number of groaning episodes/bradypneic events during the night varied from 40 to 182 (total number 725). The duration of bradypnea was from 2 to 46 s (mean duration 12.5 s). Groaning episodes prevailed in REM sleep (76.5%). The rate for NREM 2 was 21.5%, and only sporadic episodes were noted in delta sleep (1.9%); 63.3% of the events were associated with arousals, and in 94% of them an arousal occurred before or together with the onset of bradypnea. The arousal index was increased in 5 patients (mean 20.4). Bruxism was present in 4 cases, in 1 patient appearing in close association with groaning episodes. Ronchopathy was noted in 4 cases.ConclusionAlmost two-thirds of the groaning episodes were connected with arousals. Hypothetically, nocturnal groaning may well be a source of sleep disruption (mainly REM) in some cases. Because an arousal mostly preceded or coincided with groaning we believe that arousal mechanisms may be involved in the pathogenesis of nocturnal groaning.