title: Frailty and the degradation of complex balance dynamics during a dual-task protocol.
abstract: 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.
authors.affiliation: Institute for Aging Research, Hebrew SeniorLife, 1200 Centre Street, Boston, MA 02131, USA. hyungukang@hrca.harvard.edu
authors.forename: Hyun Gu
authors.initials: HG
authors.lastname: Kang
authors.forename: Madalena D
authors.initials: MD
authors.lastname: Costa
authors.forename: Attila A
authors.initials: AA
authors.lastname: Priplata
authors.forename: Olga V
authors.initials: OV
authors.lastname: Starobinets
authors.forename: Ary L
authors.initials: AL
authors.lastname: Goldberger
authors.forename: Chung-Kang
authors.initials: CK
authors.lastname: Peng
authors.forename: Dan K
authors.initials: DK
authors.lastname: Kiely
authors.forename: L Adrienne
authors.initials: LA
authors.lastname: Cupples
authors.forename: Lewis A
authors.initials: LA
authors.lastname: Lipsitz
mesh_terms: 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
references.citation: Europhys Lett. 2007 Mar;77:68008
references.pmid: 17710211
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2005 Feb;71(2 Pt 1):021906
references.pmid: 15783351
references.citation: Med Sci Sports Exerc. 2007 Mar;39(3):469-79
references.pmid: 17473773
references.citation: J Gerontol A Biol Sci Med Sci. 2002 Mar;57(3):B115-25
references.pmid: 11867648
references.citation: Proc Natl Acad Sci U S A. 1991 Mar 15;88(6):2297-301
references.pmid: 11607165
references.citation: Proc Am Thorac Soc. 2006 Aug;3(6):467-71
references.pmid: 16921107
references.citation: Am J Physiol Regul Integr Comp Physiol. 2002 Sep;283(3):R789-97
references.pmid: 12185014
references.citation: J Gerontol A Biol Sci Med Sci. 2008 Oct;63(10):1063-8
references.pmid: 18948556
references.citation: J Gerontol A Biol Sci Med Sci. 2001 Mar;56(3):M146-56
references.pmid: 11253156
references.citation: J Electrocardiol. 1995;28 Suppl:59-65
references.pmid: 8656130
references.citation: IEEE Trans Biomed Eng. 1996 Sep;43(9):956-66
references.pmid: 9214811
references.citation: Adv Adapt Data Anal. 2009 Jan 1;1(1):61-70
references.pmid: 20041035
references.citation: Biometrics. 1986 Mar;42(1):121-30
references.pmid: 3719049
references.citation: Endocr Regul. 2002 Jun;36(2):63-72
references.pmid: 12207555
references.citation: J Gerontol A Biol Sci Med Sci. 2001 Mar;56(3):M158-66
references.pmid: 11253157
references.citation: J Neuroeng Rehabil. 2007 Oct 30;4:42
references.pmid: 17971209
references.citation: Exp Brain Res. 2007 Jul;181(1):1-11
references.pmid: 17401553
references.citation: J Appl Physiol (1985). 2003 Nov;95(5):1851-60
references.pmid: 14555665
references.citation: Clin Sci (Lond). 1997 Jun;92(6):543-50
references.pmid: 9205413
references.citation: Cardiovasc Eng. 2008 Jun;8(2):88-93
references.pmid: 18172763
references.citation: BMC Geriatr. 2008 Jul 18;8:16
references.pmid: 18638389
references.citation: Gerontology. 2007;53(5):274-81
references.pmid: 17510558
references.citation: Exp Brain Res. 2008 Nov;191(3):265-76
references.pmid: 18696056
references.citation: J Clin Epidemiol. 1993 Feb;46(2):153-62
references.pmid: 8437031
references.citation: J Gerontol. 1994 Mar;49(2):M85-94
references.pmid: 8126356
references.citation: Neurobiol Aging. 2002 Jan-Feb;23(1):1-11
references.pmid: 11755010
references.citation: J Nutr Health Aging. 2000;4(3):143-55
references.pmid: 10936901
references.citation: Brain Res Cogn Brain Res. 2003 May;16(3):434-40
references.pmid: 12706223
references.citation: Gerontology. 2001 Jul-Aug;47(4):189-94
references.pmid: 11408723
references.citation: Phys Rev Lett. 2002 Aug 5;89(6):068102
references.pmid: 12190613