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- Title
Variability in Hourly Activity Levels: Statistical Noise or Insight Into Older Adult Frailty?
- Authors
Huisingh-Scheetz, Megan; Wroblewski, Kristen; Waite, Linda; Huang, Elbert S; Schumm, L Philip; Hedeker, Donald
- Abstract
<bold>Background: </bold>Frailty is associated with lower mean activity; however, hourly activity is highly variable among older individuals. We aimed to relate frailty to hourly activity variance beyond frailty's association with mean activity.<bold>Method: </bold>Using the 2010-2011 National Social Life, Health and Aging Project wrist accelerometry data (n = 647), we employed a mixed-effects location scale model to simultaneously determine whether an adapted phenotypic frailty scale (0-4) was associated with the log10-mean hourly counts per minute (cpm) and between-and within-subject hourly activity variability, adjusting for demographics, health characteristics, season, day-of-week, and time-of-day. We tested the significance of a Frailty × Time-of-day interaction and whether adjusting for sleep time altered relationships.<bold>Results: </bold>Each additional frailty point was associated with a 7.6% (10-0.0343, β = -0.0343; 95% CI: -0.05, -0.02) lower mean hourly cpm in the morning, mid-day, and late afternoon but not evening. Each frailty point was also associated with a 24.5% (e0.219, β = 0.219; 95% CI: 0.09, 0.34) greater between-subject hourly activity variance across the day; a 7% (e0.07, β = 0.07; 95% CI: 0.01¸ 0.13), 6% (e0.06, β = 0.06; 95% CI: 0, 0.12), and 10% (e0.091, β = 0.091; 95% CI: 0.03, 0.15) greater within-subject hourly activity variance in the morning, mid-day, and late afternoon, respectively; and a 6% (e-0.06, β = -0.06; 95% CI: -0.12, -0.003) lower within-subject hourly activity variance in the evening. Adjusting for sleep time did not alter results.<bold>Conclusions: </bold>Frail adults have more variable hourly activity levels than robust adults, a potential novel marker of vulnerability. These findings suggest a need for more precise activity assessment in older adults.
- Subjects
OLDER people; ADULTS; MODELS &; modelmaking; STATISTICAL hypothesis testing; NOISE
- Publication
Journals of Gerontology Series A: Biological Sciences & Medical Sciences, 2021, Vol 76, Issue 9, p1608
- ISSN
1079-5006
- Publication type
journal article
- DOI
10.1093/gerona/glaa262