title: Habitual sleep/wake patterns in the Old Order Amish: heritability and association with non-genetic factors.
abstract: OBJECTIVE
  We sought to evaluate the contribution of genetic and non-genetic factors on habitual sleep/wake patterns in a community-dwelling agrarian population using a physical activity monitoring device, the Actical.
  
  
  METHODS
  Cross-sectional population-based study of healthy Old Order Amish enrolled in the Heredity and Phenotype Intervention (HAPI) Heart Study.
  
  
  METHODS
  Lancaster County, PA, USA.
  
  
  METHODS
  723 healthy adults (54% men) with a mean age of 43.3 ± 13.8 years (range: 20-80). 96% of the subjects were connected into one 5-generation pedigree.
  
  
  METHODS
  N/A.
  
  
  METHODS
  Participants wore Actical accelerometers 24 hours/day for 7 days to determine physical activity level, as well as habitual wake time, bedtime, and sleep duration. Participants completed the Horne-Östberg Morningness-Eveningness Questionnaire (MEQ), a modified Epworth Sleepiness Scale (ESS), and a lifestyle questionnaire. A sub-study of 164 participants kept sleep diaries.
  
  
  RESULTS
  Habitual wake time and bedtime determined by Actical were highly correlated with results from sleep diaries (r = 0.82 for wake time and 0.72 for bedtime, both P < 0.0001). After adjustment for age, sex, occupation, and season, higher activity level was associated with earlier wake time but not with bedtime, and correspondingly with shorter sleep duration. After adjustment for the aforementioned factors and the effects of a shared household, habitual wake time, MEQ score, and ESS score showed significant heritability (wake time h(2) = 0.20, MEQ h(2) = 0.21, and ESS h(2) = 0.17).
  
  
  CONCLUSIONS
  Objectively measured wake time, self-reported morningness-eveningness preference, and daytime sleepiness appear heritable and wake time may be associated with physical activity level.
authors.affiliation: Departments of Medicine and Epidemiology & Biostatistics, University of California, San Francisco, CA, USA.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Evans
authors.forename: Soren
authors.initials: S
authors.lastname: Snitker
authors.forename: Shih-Hsuan
authors.initials: SH
authors.lastname: Wu
authors.forename: Aaloke
authors.initials: A
authors.lastname: Mody
authors.forename: Omer T
authors.initials: OT
authors.lastname: Njajou
authors.forename: Michael L
authors.initials: ML
authors.lastname: Perlis
authors.forename: Philip R
authors.initials: PR
authors.lastname: Gehrman
authors.forename: Alan R
authors.initials: AR
authors.lastname: Shuldiner
authors.forename: Wen-Chi
authors.initials: WC
authors.lastname: Hsueh
mesh_terms: D056044:Actigraphy; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002940:Circadian Rhythm / Q000235:genetics*; D003430:Cross-Sectional Studies; D005006:Ethnicity / Q000235:genetics* / Q000523:psychology; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D010414:Pennsylvania; D012890:Sleep / Q000235:genetics; D011795:Surveys and Questionnaires; D014851:Wakefulness / Q000235:genetics; D055815:Young Adult