title: Physical activity and sleep: Day-to-day associations among individuals with and without Bipolar Disorder.
abstract: OBJECTIVE
  To evaluate the relative role of psychopathology in the relationship between physical activity and sleep, the present study investigated the day-to-day relationship between physical activity and sleep in individuals without a psychiatric disorder and individuals with bipolar disorder using a longitudinal, naturalistic design.
  
  
  METHODS
  Participants in two groups-a healthy group with no psychiatric illness (N=36) and an inter-episode bipolar disorder group (N=32)- were studied over a two-month period. Physical health was assessed by the SF-36. Daily subjective and objective measures of physical activity and sleep were collected. A total of 6,670 physical activity measurements and 6,548 sleep measurements were logged.
  
  
  RESULTS
  The bipolar disorder group exhibited poorer physical health on the SF-36 and more sleep disturbance relative to the healthy group. No group differences were found in physical activity, nor in models examining the relationship between physical activity and sleep. Hierarchical linear models indicated that for every standard deviation increase in sleep disturbance (i.e., increased total wake time), there was a three percent decrease in subsequent day physical activity, in both the healthy and bipolar groups. Increased physical activity was associated with improved sleep for participants who reported greater average sleep disturbance.
  
  
  CONCLUSIONS
  The results for all participants in the study suggest that reduced physical activity and sleep difficulties may be mutually maintaining processes, particularly for individuals who suffer from poor sleep. Findings also raise the potential importance of targeting physical activity and sleep concurrently in interventions aimed at improving physical and mental health.
authors.affiliation: Columbia University Medical Center, New York State Psychiatric Institute.
authors.forename: Eleanor L
authors.initials: EL
authors.lastname: McGlinchey
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine.
authors.forename: Anda
authors.initials: A
authors.lastname: Gershon
authors.affiliation: San Francisco Bay Area Center for Cognitive Therapy.
authors.forename: Polina
authors.initials: P
authors.lastname: Eidelman
authors.affiliation: Department of Psychology, University of California, Berkeley.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Kaplan
authors.affiliation: Department of Psychology, University of California, Berkeley.
authors.forename: Allison G
authors.initials: AG
authors.lastname: Harvey
keywords: Actigraphy; Bipolar Disorder; Physical Activity; Physical Health; Sleep