REM SLEEP BEHAVIOUR DISORDER IN THE ELDERLY HELEN F. K. CHIU 1 à , Y. K. WING 1 , DICKY W. S. CHUNG 2 AND CROVER K. W. HO 3 1 Associate Professor, Department of Psychiatry, Chinese University of Hong Kong, Hong Kong 2 Senior Medical Ocer, Department of Psychiatry, Chinese University of Hong Kong, Hong Kong 3 Chief Technologist, Department of Psychiatry, Chinese University of Hong Kong, Hong Kong ABSTRACT REM sleep behaviour disorder is a recently described parasomnia characterized by a history of excessive motor activities during sleep and is associated with pathological absence of muscle atonia during REM sleep. There is very limited literature on the condition. Two out of 349 elderly patients referred to a psychogeriatric unit were identi®ed to have REM sleep behaviour disorder. These two patients are presented to illustrate the clinical features of the condition. Both of them showed a good response to clonazepam treatment. # 1997 John Wiley & Sons, Ltd. Int. J. Geriat. Psychiatry, 12, 888±891, 1997. No. of Figures: 0. No. of Tables: 0. No. of References: 12. KEY WORDS ÐREM sleep behaviour disorder; elderly; clinical features Sleep disorders are common in the elderly, and insomnia and sleep apnoea syndromes have been particularly widely studied. In recent years, a new disorder, rapid eye movement sleep behaviour disorder (RBD) has been described (Schenck et al., 1985). Normal REM sleep is associated with muscle paralysis that spares the diaphragm and extraocular muscle which probably acts as a pro- tective measure against the acting out of dreams. RBD is a parasomnia characterized by a history of excessive motor activities during nocturnal sleep which may lead to physical injuries and is associ- ated with pathological absence of muscle atonia during REM sleep (Schenck et al., 1986) in polygraphic studies. The presenting features are usually vigorous sleep behaviour accompanying vivid dreams which may result in repeated injuries, including ecchymoses, lacerations and fractures or disturbance to patients' bed partners. It is more common in elderly males and the mean age of presentation is 59:3 + 15:4 years in a series of 70 patients with the disorder (Schenck and Mahowald, 1990). Currently, RBD is a recognized diagnostic category in DSM-IV (1994) coded under parasomnia not otherwise speci®ed. As this entity has only been recently described, there is very limited literature on the condition. We identi®ed two patients with RBD among 349 in- and outpatient referrals to the psychogeriatric unit of the Chinese University of Hong Kong based in a general hospital over a 2-year period. Our unit serves a catchment area of 0.75 million general population, 8.7% of whom are aged 65 or above. Both patients underwent detailed polysomno- graphic study with video recording overnight in a sleep laboratory. Polysomnographic monitoring included electrooculogram (EOG), EEG, electro- myogram (EMG, chin, bilateral anterior tibialis muscle and bilateral extensor digitorum muscle), ECG, nasal±oral air¯ow and respiratory move- ments. They satis®ed the diagnostic criteria for RBD according to Mahowald and Schenck (1990), which are as follows: 1. History of problem sleep behaviour that is harmful or potentially harmful, or disruptive of sleep continuity or annoying to self or bed partner 2. Polysomnographic abnormality of either excessive augmentation of chin EMG tone or excessive chin or limb EMG twitching during REM sleep à Correspondence to: Dr H. F. K. Chiu, Department of Psychiatry, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong. Fax: (852) 2637 7884. CCC 0885±6230/97/090888±04$17.50 Received 15 October 1996 # 1997 John Wiley & Sons, Ltd. Accepted 26 February 1997 INTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, VOL. 12: 888±891 (1997)