Relationship between ethnicity and sleep patterns in normal controls: implications for psychopathology and treatment Uma Rao a, b, c, *, Russell E. Poland a, b, c , Preetam Lutchmansingh a , Georey E. Ott a , James T. McCracken a, b, c , Keh-Ming Lin a, b a Department of Psychiatry, Harbor-UCLA Medical Center, Torrance, CA, USA b Department of Psychiatry UCLA School of Medicine, Los Angeles, CA, USA c Brain Research Institute, UCLA School of Medicine, Los Angeles, CA, USA Received 12 November 1998; received in revised form 15 April 1999; accepted 26 April 1999 Abstract The purpose of the study was to examine ethnic in¯uences on sleep regulation. Seventy-three normal volunteers from four ethnic groups (17 African-Americans, 10 Asians, 30 Caucasians and 16 Hispanics) were studied for two consecutive nights with sleep polysomnography recordings in the laboratory. The subjects were in good physical and psychological health, and were asymptomatic with respect to sleep/wake complaints or sleep disorders. With the exception of minor dierences, sleep continuity, sleep architecture and rapid eye movement (REM) sleep patterns were comparable among the four groups. African-Americans had evidence of more stages 1 and 2 and diminished stage 4 sleep, whereas the Hispanics had higher REM density. These preliminary ®ndings suggest that sleep patterns are remarkably similar across cultures. There are, however, important cross- ethnic dierences, speci®cally in the depth of sleep and in phasic REM measures. Because sleep disturbances are common symptoms of emotional disorders and since many psychoactive agents aect sleep, cross-ethnic dierences in sleep patterns may have potential implications for the treatment and prevention of psychiatric disorders. # 1999 Elsevier Science Ltd. All rights reserved. Keywords: Ethnicity; Normal; Psychopathology; Sleep regulation; Socio-cultural; Treatment 1. Introduction Diculties with sleep are among the most common symptoms of emotional disorders. For example, per- sistent insomnia is a harbinger of anxiety, mood and substance use disorders (Ford and Kamerow, 1989; Breslau et al., 1996; Perlis et al., 1997). In an attempt to identify biological markers for major psychiatric disorders, numerous electroencephalographic (EEG) sleep studies have been performed in the past three decades. In 1992, Benca and colleagues published a meta-analytic review of EEG sleep investigations from 177 controlled studies in 7151 patients and controls. The psychiatric conditions included alcoholism, anxiety disorders, borderline personality disorder, dementia, eating disorders, insomnia, mood disorders, narcolepsy and schizophrenia. Benca et al. (1992) concluded that most psychiatric groups showed evidence of reduced sleep eciency and total sleep time, speci®cally with decrements in non-rapid eye movement sleep. Although rapid eye movement (REM) sleep was rela- tively well preserved in all groups, altered REM pat- terns were observed as well, most frequently in mood disorders. With the identi®cation of objective sleep changes in association with emotional disorders, investigators have begun to use more sophisticated designs, particu- Journal of Psychiatric Research 33 (1999) 419±426 0022-3956/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0022-3956(99)00019-9 www.elsevier.com/locate/jpsychires * Corresponding author. Present address: UCLA Neuropsychiatric Institute, 760 Westwood Plaza, Room 68-237, Los Angeles, CA 90024-1759, USA. Tel.: +1-310-206-9478; fax: +1-310-825-2682. E-mail address: urao@mednet.ucla.edu (U. Rao)