title: A comparison of subjective and objective measures of physical activity from the Newcastle 85+ study.
abstract: BACKGROUND
  Little is known about physical activity (PA) in the very old, the fastest growing age group in the population. We aimed to examine the convergent validity of subjective and objective measures of PA in adults aged over 85 years.
  
  
  METHODS
  A total of 484 participants aged 87-89 years recruited to the Newcastle 85+ study completed a purpose-designed physical activity questionnaire (PAQ), which categorised participants as mildly active, moderately active and very active. Out of them, 337 participants wore a triaxial, raw accelerometer on the right wrist over a 5-7-day period to obtain objective measures of rest/activity, PA intensity and PA type. Data from subjective and objective measurement methods were compared.
  
  
  RESULTS
  Self-reported PA was significantly associated with objective measures of the daily sedentary time, low-intensity PA and activity type classified as sedentary, activities of daily living and walking. Objective measures of PA were significantly different when low, moderate and high self-reported PA categories were compared (all P < 0.001).
  
  
  CONCLUSIONS
  The Newcastle 85+ PAQ demonstrated convergent validity with objective measures of PA. Our findings suggest that this PAQ can be used in the very old to rank individuals according to their level of total PA.
authors.affiliation: Newcastle Institute for Ageing, Newcastle University, The Medical School, 4th Floor William Leech Building, Newcastle upon Tyne NE2 4HH, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Innerd
authors.affiliation: Newcastle Institute for Ageing, Newcastle University, The Medical School, 4th Floor William Leech Building, Newcastle upon Tyne NE2 4HH, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Catt
authors.affiliation: Institute of Health and Society, Newcastle University, Baddiley-Clark Building, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK.
authors.forename: Joanna
authors.initials: J
authors.lastname: Collerton
authors.affiliation: Institute of Health and Society, Newcastle University, Baddiley-Clark Building, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK.
authors.forename: Karen
authors.initials: K
authors.lastname: Davies
authors.affiliation: Institute of Cellular Medicine, Newcastle University, William Leech Building, Newcastle upon Tyne, NE2 4HH, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Trenell
authors.affiliation: Newcastle Institute for Ageing, Campus for Ageing and Vitality, Newcastle upon Tyne, NE4 5PL, UK.
authors.forename: Thomas B L
authors.initials: TB
authors.lastname: Kirkwood
authors.affiliation: Newcastle Institute for Ageing, Campus for Ageing and Vitality, Newcastle upon Tyne, NE4 5PL, UK.
authors.forename: Carol
authors.initials: C
authors.lastname: Jagger
mesh_terms: D056044:Actigraphy / Q000379:methods*; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D057566:Self Report; D011795:Surveys and Questionnaires; D006113:United Kingdom; D016138:Walking / Q000502:physiology*
keywords: accelerometry; older people; physical activity; questionnaire; self-report; ‘aged 80 and over’