title: Sleep patterns among rural Chinese twin adolescents.
abstract: OBJECTIVE
  To examine sleep patterns and influencing factors (age, gender, Tanner Stage, weekday vs. weekend, and pre-sleep activity) among rural Chinese adolescents.
  
  
  METHODS
  This is a prospective study among 621 adolescents aged 11-20 years (341 males) using both a questionnaire and sleep diary to obtain bedtime, wake-up time, sleep latency, and total sleep time (TST).
  
  
  RESULTS
  The median TST was 8.6h on weekdays and 9.4h on weekends. Despite absence of late night social pressure and computers, a U-shaped TST pattern was observed across age and Tanner Stage, with a nadir around age 15-16 years or Tanner IV. Bedtimes became progressively later with age and Tanner Stage, while wake-up time was considerably earlier for school students or up to Tanner IV. Later wake-up times and longer TST on weekends were seen in school students, but not in non-school adolescents (>17 years). Pre-sleep activity, like reading or studying, was related to later bedtime, earlier wake-up time, and shorter TST in both genders.
  
  
  CONCLUSIONS
  Age, Tanner Stage, and pre-sleep activity affected sleep patterns in this sample of rural Chinese adolescents. Later bedtime coupled with earlier wake-up time associated with academic demand appear to be important contributors to sleep loss among school students.
authors.affiliation: Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: Fengxiu
authors.initials: F
authors.lastname: Ouyang
authors.forename: Brandon S
authors.initials: BS
authors.lastname: Lu
authors.forename: Binyan
authors.initials: B
authors.lastname: Wang
authors.forename: Jianhua
authors.initials: J
authors.lastname: Yang
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Li
authors.forename: Liuliu
authors.initials: L
authors.lastname: Wang
authors.forename: Genfu
authors.initials: G
authors.lastname: Tang
authors.forename: Houxun
authors.initials: H
authors.lastname: Xing
authors.forename: Xiping
authors.initials: X
authors.lastname: Xu
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Chervin
authors.forename: Phyllis C
authors.initials: PC
authors.lastname: Zee
authors.forename: Xiaobin
authors.initials: X
authors.lastname: Wang