title: Bidirectional associations of accelerometer-determined sedentary behavior and physical activity with reported time in bed: Women's Health Study.
abstract: To examine the day-to-day, bidirectional associations of accelerometer-derived sedentary behavior and physical activity (PA) with reported time in bed in a large cohort of older women.
  
  
  
  Data are from 10086 Women's Health Study participants (aged 71.6 years; SD, 5.7) who agreed to wear an accelerometer and complete a diary for 7 consecutive days. Generalized linear (multilevel) models with repeated measures were used to examine the adjusted associations of the following: (1) reported time in bed with next-day accelerometer-determined counts and time spent sedentary and in light- and moderate-to-vigorous-intensity PA (MVPA) and (2) accelerometer estimates with reported time in bed that night, expressed as short (<7 hours), optimal (7-9 hours), and long (>9 hours) sleep.
  
  
  
  Across days, short sleep was associated with an average of 5500 (SE, 1352) higher accelerometer counts the following day but was also related to higher average sedentary (46.5 [SE, 1.5] minutes) and light-intensity PA (11.9 [SE, 1.2] minutes) than optimal sleep (all P<.001). Long sleep was associated with lower accelerometer counts, time spent sedentary and in light-intensity PA, and a reduced likelihood of engaging in ≥20 minutes of MVPA (all P<.001) than optimal sleep. Higher PA during the day (higher accelerometer counts and ≥20 minutes of accumulated MVPA) was associated with a reduced likelihood of reporting short or long sleep that night (all P<.001).
  
  
  
  Findings support the bidirectional associations of accelerometer-determined sedentary behavior and PA with reported time in bed in older women. Future studies are needed to confirm findings with sleep actigraphy in older women.
authors.affiliation: Department of Epidemiology, Human Genetics and Environmental Sciences, University of Texas Health Science Center in Houston, School of Public Health-Austin Campus, Austin, TX 78701. Electronic address: Kelley.P.Gabriel@uth.tmc.edu.
authors.forename: Kelley
authors.initials: K
authors.lastname: Pettee Gabriel
authors.affiliation: Division of Research, Kaiser Permanente Northern California, Oakland, CA 94612.
authors.forename: Barbara
authors.initials: B
authors.lastname: Sternfeld
authors.affiliation: Division of Preventive Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA; Department of Epidemiology, Harvard TH Chan School of Public Health, Boston, MA; National Institute on Aging, National Institutes of Health, Bethesda, MD.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Shiroma
authors.affiliation: Department of Biostatistics, University of Texas Health Science Center in Houston, School of Public Health-Austin Campus, Austin, TX 78701.
authors.forename: Adriana
authors.initials: A
authors.lastname: Pérez
authors.affiliation: Stanford Center for Sleep Sciences and Medicine, Stanford University; Palo Alto, CA 94304.
authors.forename: Joseph
authors.initials: J
authors.lastname: Cheung
authors.affiliation: Division of Preventive Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA; Department of Epidemiology, Harvard TH Chan School of Public Health, Boston, MA.
authors.forename: I-Min
authors.initials: IM
authors.lastname: Lee
mesh_terms: D061725:Accelerometry; D000368:Aged; D015331:Cohort Studies; D015444:Exercise; D005260:Female; D006801:Humans; D057185:Sedentary Behavior; D012890:Sleep; D013997:Time Factors; D016387:Women's Health
keywords: Accelerometer; Epidemiological methods; Exercise; Older women; Sleep