title: Comparison of Self-Reported and Accelerometer-Assessed Physical Activity in Older Women.
abstract: BACKGROUND
  Self-reported physical activity measures continue to be validated against accelerometers; however, the absence of standardized, accelerometer moderate-to-vigorous physical activity (MVPA) definitions has made comparisons across studies difficult. Furthermore, recent accelerometer models assess accelerations in three axes, instead of only the vertical axis, but validation studies have yet to take incorporate triaxial data.
  
  
  METHODS
  Participants (n = 10 115) from the Women's Health Study wore a hip-worn accelerometer (ActiGraph GT3X+) for seven days during waking hours (2011-2014). Women then completed a physical activity questionnaire. We compared self-reported with accelerometer-assessed MVPA, using four established cutpoints for MVPA: three using only vertical axis data (760, 1041 and 1952 counts per minute (cpm)) and one using triaxial data (2690 cpm).
  
  
  RESULTS
  According to self-reported physical activity, 66.6% of women met the US federal physical activity guidelines, engaging in ≥150 minutes per week of MVPA. The percent of women who met guidelines varied widely depending on the accelerometer MVPA definition (760 cpm: 50.0%, 1041 cpm: 33.0%, 1952 cpm: 13.4%, and 2690 cpm: 19.3%).
  
  
  CONCLUSIONS
  Triaxial count data do not substantially reduce the difference between self-reported and accelerometer-assessed MVPA.
authors.affiliation: Division of Preventive Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, United States of America.|Department of Epidemiology, Harvard School of Public Health, Boston, MA, United States of America.|Laboratory of Epidemiology and Population Science, Intramural Research Program of the National Institutes of Health, National Institute on Aging, Bethesda, MD, United States of America.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Shiroma
authors.affiliation: Division of Preventive Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, United States of America.|Department of Epidemiology, Harvard School of Public Health, Boston, MA, United States of America.
authors.forename: Nancy R
authors.initials: NR
authors.lastname: Cook
authors.affiliation: Division of Preventive Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, United States of America.|Department of Epidemiology, Harvard School of Public Health, Boston, MA, United States of America.
authors.forename: JoAnn E
authors.initials: JE
authors.lastname: Manson
authors.affiliation: Division of Preventive Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, United States of America.|Department of Epidemiology, Harvard School of Public Health, Boston, MA, United States of America.
authors.forename: Julie E
authors.initials: JE
authors.lastname: Buring
authors.affiliation: Division of Preventive Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, United States of America.|Department of Epidemiology, Harvard School of Public Health, Boston, MA, United States of America.|Department of Nutrition, Harvard School of Public Health, Boston, MA, United States of America.
authors.forename: Eric B
authors.initials: EB
authors.lastname: Rimm
authors.affiliation: Division of Preventive Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, United States of America.|Department of Epidemiology, Harvard School of Public Health, Boston, MA, United States of America.
authors.forename: I-Min
authors.initials: IM
authors.lastname: Lee
mesh_terms: D061725:Accelerometry; D000368:Aged; D005260:Female; D006801:Humans; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods*; D009043:Motor Activity; D057566:Self Report