Intra-individual daily and yearly variability in actigraphically recorded sleep measures: the CARDIA study.

Published

Journal Article

STUDY OBJECTIVES:To describe the day-to-day and year-to-year variation in sleep characteristics among early middle-aged adults. DESIGN:Participants wore an Actiwatch (Mini Mitter, Inc) for 3 days on two occasions approximately 1 year apart. PARTICIPANTS:N = 669 participants aged 38-50 years from the Chicago site of the Coronary Artery Risk Development in Young Adults (CARDIA) cohort study. MEASUREMENTS AND RESULTS:Sleep measures included sleep duration, sleep latency, sleep efficiency, and time in bed. For each sleep parameter, total variance was decomposed into between-subject variance, within-subject variance from day to day, and within-subject variance from year to year. The standard deviation was calculated from the variance. Analysis yielded a within-subject daily standard deviation (SD) of 1.26 hours and a within-subject yearly SD of 0.39 hours for sleep duration. Daily SD was 30.7 minutes and yearly SD was 6.3 minutes for within-subject variability of sleep latency. Daily SD was 8.4% and yearly SD was 2.7% for within-subject variability of sleep efficiency. Finally, daily SD was 1.31 hours and yearly SD was 0.52 hours for within-subject variability of time in bed. CONCLUSIONS:For each of the 4 sleep characteristics, nightly variability was much greater than yearly variability, meaning sleep behavior changes little in one year in this cohort of early middle-aged adults, despite large daily fluctuations. These results have important methodological implications, including that single-day measures of sleep may not accurately reflect habitual behavior.

Full Text

Duke Authors

Cited Authors

  • Knutson, KL; Rathouz, PJ; Yan, LL; Liu, K; Lauderdale, DS

Published Date

  • June 2007

Published In

Volume / Issue

  • 30 / 6

Start / End Page

  • 793 - 796

PubMed ID

  • 17580601

Pubmed Central ID

  • 17580601

Electronic International Standard Serial Number (EISSN)

  • 1550-9109

International Standard Serial Number (ISSN)

  • 0161-8105

Digital Object Identifier (DOI)

  • 10.1093/sleep/30.6.793

Language

  • eng