title: Sleep and cognitive problems in patients with attention-deficit hyperactivity disorder.
abstract: OBJECTIVE
  Attention-deficit hyperactivity disorder (ADHD) is characterized by inattentive and impulsive behavior. Many ADHD patients reportedly have cognitive dysfunction and sleep problems, including longer sleep latency, lower sleep efficiency, and shorter total sleep time. The purpose of this study was to examine neurocognitive functions and nocturnal sleep parameters in patients with ADHD, using a cognitive function test and actigraphy.
  
  
  METHODS
  Subjects included 37 male patients with ADHD and 32 controls (7-12 years of age). For each participant, we determined intelligence quotient (IQ) and administered the Matching Familiar Figures Test (MFFT) and 72-hour actigraphy. The relationships between sleep parameters and cognitive functions were assessed.
  
  
  RESULTS
  ADHD patients significantly differed from controls in several cognitive functions and sleep variables. In the MFFT, response error rate (P<0.001) and error counts (P=0.003) were significantly increased in ADHD patients compared with control children. MFFT response latency was significantly shorter in ADHD patients than in controls (P<0.001). In addition, sleep latency (P=0.01), wake after sleep onset (WASO) (P<0.001), and fragmentation index (P<0.001) were evaluated by actigraphy and found to be significantly increased in patients with ADHD compared with controls. However, no significant differences in total sleep time or sleep efficiency were observed. WASO and response error rates were positively correlated in patients with ADHD (rho =0.52, P=0.012). Furthermore, fragmentation index sleep variables were significantly positively correlated with response error (rho =0.44, P=0.008) and response latency rates (rho =0.4, P=0.018) in the MFFT. Reaction error rate was significantly associated with the fragmentation index (beta =0.94, P=0.024).
  
  
  CONCLUSIONS
  Patients with ADHD had more sleep problems, including significantly increased sleep latency, WASO, and fragmentation index, and poorer cognitive function, compared with controls. Some of these sleep problems, including WASO and the fragmentation index, were positively correlated with impulsivity, illustrated by the cognitive function tests in patients with ADHD. However, further studies with large sample sizes and the addition of polysomnography and determination of ADHD subtypes should be performed to confirm our results regarding sleep and cognitive problems in patients with ADHD.
authors.affiliation: Department of Psychiatry, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Hae Kook
authors.initials: HK
authors.lastname: Lee
authors.affiliation: Department of Psychiatry, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Jong-Hyun
authors.initials: JH
authors.lastname: Jeong
authors.affiliation: Department of Psychiatry, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Na-Young
authors.initials: NY
authors.lastname: Kim
authors.affiliation: Department of Psychiatry, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Min-Hyeon
authors.initials: MH
authors.lastname: Park
authors.affiliation: Department of Psychiatry, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Tae-Won
authors.initials: TW
authors.lastname: Kim
authors.affiliation: Department of Psychiatry, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Ho-Jun
authors.initials: HJ
authors.lastname: Seo
authors.affiliation: Department of Psychiatry, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Hyun-Kook
authors.initials: HK
authors.lastname: Lim
authors.affiliation: Department of Psychiatry, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Seung-Chul
authors.initials: SC
authors.lastname: Hong
authors.affiliation: Department of Psychiatry, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Jin-Hee
authors.initials: JH
authors.lastname: Han
keywords: ADHD; MFFT; actigraphy; sleep problems