Frailty and the degradation of complex balance dynamics during a dual-task protocol.
BACKGROUND
Balance during quiet stance involves the complex interactions of multiple postural control systems, which may degrade with frailty. The complexity of center of pressure (COP) dynamics, as quantified using multiscale entropy (MSE), during quiet standing is lower in older adults, especially those with falls. We hypothesized that COP dynamics from frail elderly individuals demonstrate less complexity than those from nonfrail elderly controls; complexity decreases when performing a dual task; and postural complexity during quiet standing is independent of other conventional correlates of balance control, such as age and vision.


METHODS
We analyzed data from a population-based study of community-dwelling older adults. Frailty phenotype (nonfrail, prefrail, or frail) was determined for 550 participants (age 77.9 +/- 5.5 years). COP excursions were quantified for 10 trials of 30 seconds each. Participants concurrently performed a serial subtraction task in half of the trials. Complexity of balance dynamics was quantified using MSE. Root-mean-square sway amplitude was also computed.


RESULTS
Of the 550, 38% were prefrail and 9% were frail. Complexity of the COP dynamics in the anteroposterior direction was lower in prefrail (8.78 +/- 1.91 [mean +/- SD]) and frail (8.38 +/- 2.13) versus nonfrail (9.20 +/- 1.74) groups (p < .001). Complexity reduced by a comparable amount in all three groups while performing the subtraction task (p < .001). Quiet standing complexity was independently associated with frailty after adjusting for covariates related to balance while sway amplitude was not.


CONCLUSIONS
Cognitive distractions during standing may further compromise balance control in frail individuals, leading to an increased risk of falls.
Kang
Hyun Gu
HG
Institute for Aging Research, Hebrew SeniorLife, 1200 Centre Street, Boston, MA 02131, USA. hyungukang@hrca.harvard.edu
Costa
Madalena D
MD
Priplata
Attila A
AA
Starobinets
Olga V
OV
Goldberger
Ary L
AL
Peng
Chung-Kang
CK
Kiely
Dan K
DK
Cupples
L Adrienne
LA
Lipsitz
Lewis A
LA
D000058:Accidental Falls / Q000517:prevention & control / Q000706:statistics & numerical data*; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001288:Attention / Q000502:physiology; D003071:Cognition / Q000502:physiology; D015331:Cohort Studies; D005260:Female; D016330:Frail Elderly; D005684:Gait / Q000502:physiology*; D015577:Geriatric Assessment; D006801:Humans; D016015:Logistic Models; D008297:Male; D051346:Mobility Limitation; D015999:Multivariate Analysis; D004856:Postural Balance / Q000502:physiology*; D011336:Probability; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time; D018570:Risk Assessment; D012678:Sensation Disorders / Q000175:diagnosis* / Q000453:epidemiology; D013647:Task Performance and Analysis
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