@article {987, title = {Gait variability and the risk of incident mobility disability in community-dwelling older adults.}, journal = {J Gerontol A Biol Sci Med Sci}, volume = {62}, year = {2007}, month = {2007 Sep}, pages = {983-8}, abstract = {

BACKGROUND: Gait speed is a strong predictor of incident walking disability. The objective was to determine if gait variability adds to the prediction of incident mobility disability independent of gait speed.

METHODS: Participants included 379 older adults (mean age = 79 years; 78\% Caucasian, and 40\% men) in the Cardiovascular Health Study at the Pittsburgh site. All could ambulate independently and reported no difficulty walking a half mile. Gait characteristics were determined from a 4-meter computerized walkway. For each gait parameter, variability was defined as the standard deviation from the individual steps from two passes. Incident walking disability was obtained by phone interview every 6 months for 54 months and was defined as new difficulty walking a half mile or inability to walk a half mile.

RESULTS: Of the 379 participants, 222 (58.6\%) developed incident mobility disability. In unadjusted Cox proportional hazards models gait speed, mean step length, mean stance time, and stance time variability were associated with incident mobility disability. After adjusting for gait speed, demographics, chronic conditions, prescription medications, health status, and physical activity level, only stance time variability remained an important indicator of disability. In the adjusted model, an increase in stance time variability of 0.01 seconds was associated with a 13\% higher incidence of mobility disability (hazard ratio 1.13, 95\% confidence interval, 1.01-1.27).

CONCLUSIONS: Stance time variability is an independent predictor of future mobility disability. Future efforts are needed to determine whether interventions that decrease stance time variability will also delay mobility disability.

}, keywords = {Aged, Aged, 80 and over, Aging, Cohort Studies, Female, Gait, Gait Disorders, Neurologic, Humans, Male, Mobility Limitation, Prospective Studies, Risk Factors, Walking}, issn = {1079-5006}, doi = {10.1093/gerona/62.9.983}, author = {Brach, Jennifer S and Studenski, Stephanie A and Perera, Subashan and VanSwearingen, Jessie M and Newman, Anne B} } @article {1065, title = {The reliability and validity of measures of gait variability in community-dwelling older adults.}, journal = {Arch Phys Med Rehabil}, volume = {89}, year = {2008}, month = {2008 Dec}, pages = {2293-6}, abstract = {

OBJECTIVE: To examine the test-retest reliability and concurrent validity of variability of gait characteristics.

DESIGN: Cross-sectional study.

SETTING: Research laboratory.

PARTICIPANTS: Older adults (N=558) from the Cardiovascular Health Study.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: Gait characteristics were measured using a 4-m computerized walkway. SD determined from the steps recorded were used as the measures of variability. Intraclass correlation coefficients (ICC) were calculated to examine test-retest reliability of a 4-m walk and two 4-m walks. To establish concurrent validity, the measures of gait variability were compared across levels of health, functional status, and physical activity using independent t tests and analysis of variances.

RESULTS: Gait variability measures from the two 4-m walks demonstrated greater test-retest reliability than those from the single 4-m walk (ICC=.22-.48 and ICC=.40-.63, respectively). Greater step length and stance time variability were associated with poorer health, functional status and physical activity (P<.05).

CONCLUSIONS: Gait variability calculated from a limited number of steps has fair to good test-retest reliability and concurrent validity. Reliability of gait variability calculated from a greater number of steps should be assessed to determine if the consistency can be improved.

}, keywords = {Activities of Daily Living, Aged, Cross-Sectional Studies, Disability Evaluation, Exercise, Female, Gait, Health Status, Humans, Male, Pennsylvania, Rehabilitation, Reproducibility of Results}, issn = {1532-821X}, doi = {10.1016/j.apmr.2008.06.010}, author = {Brach, Jennifer S and Perera, Subashan and Studenski, Stephanie and Newman, Anne B} } @article {970, title = {Stance time and step width variability have unique contributing impairments in older persons.}, journal = {Gait Posture}, volume = {27}, year = {2008}, month = {2008 Apr}, pages = {431-9}, abstract = {

Gait variability may have multiple causes. We hypothesized that central nervous system (CNS) impairments would affect motor control and be manifested as increased stance time and step length variability, while sensory impairments would affect balance and be manifested as increased step width variability. Older adults (mean+/-standard deviation (S.D.) age=79.4+/-4.1, n=558) from the Pittsburgh site of the Cardiovascular Health Study participated. The S.D. across steps was the indicator of gait variability, determined for three gait measures, step length, stance time and step width, using a computerized walkway. Impairment measures included CNS function (modified mini-mental state examination, Trails A and B, Digit Symbol Substitution, finger tapping), sensory function (lower extremity (LE) vibration, vision), strength (grip strength, repeated chair stands), mood, and LE pain. Linear regression models were fit for the three gait variability characteristics using impairment measures as independent variables, adjusted for age, race, gender, and height. Analyses were repeated stratified by gait speed. All measures of CNS impairment were directly related to stance time variability (p<0.01), with increased CNS impairment associated with increased stance time variability. CNS impairments were not related to step length or width variability. Both sensory impairments were inversely related to step width (p<0.01) but not step length or stance time variability. CNS impairments affected stance time variability especially in slow walkers while sensory impairments affected step width variability in fast walkers. Specific patterns of gait variability may imply different underlying causes. Types of gait variability should be specified. Interventions may be targeted at specific types of gait variability.

}, keywords = {Aged, Aged, 80 and over, Biomechanical Phenomena, Female, Gait Disorders, Neurologic, Humans, Linear Models, Longitudinal Studies, Male, Neuropsychological Tests, Postural Balance, Range of Motion, Articular, Risk Factors, Signal Processing, Computer-Assisted}, issn = {0966-6362}, doi = {10.1016/j.gaitpost.2007.05.016}, author = {Brach, Jennifer S and Studenski, Stephanie and Perera, Subashan and VanSwearingen, Jessie M and Newman, Anne B} } @article {1259, title = {Gait speed and survival in older adults.}, journal = {JAMA}, volume = {305}, year = {2011}, month = {2011 Jan 05}, pages = {50-8}, abstract = {

CONTEXT: Survival estimates help individualize goals of care for geriatric patients, but life tables fail to account for the great variability in survival. Physical performance measures, such as gait speed, might help account for variability, allowing clinicians to make more individualized estimates.

OBJECTIVE: To evaluate the relationship between gait speed and survival.

DESIGN, SETTING, AND PARTICIPANTS: Pooled analysis of 9 cohort studies (collected between 1986 and 2000), using individual data from 34,485 community-dwelling older adults aged 65 years or older with baseline gait speed data, followed up for 6 to 21 years. Participants were a mean (SD) age of 73.5 (5.9) years; 59.6\%, women; and 79.8\%, white; and had a mean (SD) gait speed of 0.92 (0.27) m/s.

MAIN OUTCOME MEASURES: Survival rates and life expectancy.

RESULTS: There were 17,528 deaths; the overall 5-year survival rate was 84.8\% (confidence interval [CI], 79.6\%-88.8\%) and 10-year survival rate was 59.7\% (95\% CI, 46.5\%-70.6\%). Gait speed was associated with survival in all studies (pooled hazard ratio per 0.1 m/s, 0.88; 95\% CI, 0.87-0.90; P < .001). Survival increased across the full range of gait speeds, with significant increments per 0.1 m/s. At age 75, predicted 10-year survival across the range of gait speeds ranged from 19\% to 87\% in men and from 35\% to 91\% in women. Predicted survival based on age, sex, and gait speed was as accurate as predicted based on age, sex, use of mobility aids, and self-reported function or as age, sex, chronic conditions, smoking history, blood pressure, body mass index, and hospitalization.

CONCLUSION: In this pooled analysis of individual data from 9 selected cohorts, gait speed was associated with survival in older adults.

}, keywords = {Aged, Cohort Studies, Female, Gait, Geriatric Assessment, Humans, Life Expectancy, Male, Survival Analysis, United States}, issn = {1538-3598}, doi = {10.1001/jama.2010.1923}, author = {Studenski, Stephanie and Perera, Subashan and Patel, Kushang and Rosano, Caterina and Faulkner, Kimberly and Inzitari, Marco and Brach, Jennifer and Chandler, Julie and Cawthon, Peggy and Connor, Elizabeth Barrett and Nevitt, Michael and Visser, Marjolein and Kritchevsky, Stephen and Badinelli, Stefania and Harris, Tamara and Newman, Anne B and Cauley, Jane and Ferrucci, Luigi and Guralnik, Jack} } @article {1391, title = {Cardiovascular physiology in premotor Parkinson{\textquoteright}s disease: a neuroepidemiologic study.}, journal = {Mov Disord}, volume = {27}, year = {2012}, month = {2012 Jul}, pages = {988-95}, abstract = {

Changes in cardiovascular physiology in Parkinson{\textquoteright}s disease (PD) are common and may occur prior to diagnostic parkinsonian motor signs. We investigated associations of electrocardiographic (ECG) abnormalities, orthostasis, heart rate variability, and carotid stenosis with the risk of PD diagnosis in the Cardiovascular Health Study, a community-based cohort of older adults. ECG abnormality, orthostasis (symptomatic or asymptomatic), heart rate variability (24-hour Holter monitoring), and any carotid stenosis (>=1\%) by ultrasound were modeled as primary predictors of incident PD diagnosis using multivariable logistic regression. Incident PD cases were identified by at least 1 of the following: self-report, antiparkinsonian medication use, and ICD-9. If unadjusted models were significant, they were adjusted or stratified by age, sex, and smoking status, and those in which predictors were still significant (P <= .05) were also adjusted for race, diabetes, total cholesterol, low-density lipoprotein, blood pressure, body mass index, physical activity, education level, stroke, and C-reactive protein. Of 5888 participants, 154 incident PD cases were identified over 14 years of follow-up. After adjusting models with all covariates, those with any ECG abnormality (odds ratio [OR], 1.45; 95\% CI, 1.02-2.07; P = .04) or any carotid stenosis (OR, 2.40; 95\% CI, 1.40-4.09; P = .001) at baseline had a higher risk of incident PD diagnosis. Orthostasis and heart rate variability were not significant predictors. This exploratory study suggests that carotid stenosis and ECG abnormalities occur prior to motor signs in PD, thus serving as potential premotor features or risk factors for PD diagnosis. Replication is needed in a population with more thorough ascertainment of PD onset.

}, keywords = {Aged, Antiparkinson Agents, Cardiovascular Physiological Phenomena, Carotid Stenosis, Cohort Studies, Data Interpretation, Statistical, Dizziness, Electrocardiography, Female, Heart Rate, Hospitalization, Humans, Longitudinal Studies, Male, Movement Disorders, Neurologic Examination, Parkinson Disease, Risk, Ultrasonography}, issn = {1531-8257}, doi = {10.1002/mds.24979}, author = {Jain, Samay and Ton, Thanh G and Perera, Subashan and Zheng, Yan and Stein, Phyllis K and Thacker, Evan and Strotmeyer, Elsa S and Newman, Anne B and Longstreth, Will T} } @article {7131, title = {Digit Symbol Substitution test and future clinical and subclinical disorders of cognition, mobility and mood in older adults.}, journal = {Age Ageing}, volume = {45}, year = {2016}, month = {2016 Sep}, pages = {688-95}, abstract = {

OBJECTIVE: to examine whether psychomotor speed predicts individual and combined disorders in cognition, mobility and mood and if white matter hyperintensities explain these associations.

DESIGN AND SETTING: longitudinal; Cardiovascular Health Study.

SUBJECTS: 5,888 participants (57.6\% women, 15.7\% black, 75.1 (5.5), mean years (SD)).

METHODS: psychomotor speed (Digit Symbol Substitution Test (DSST)) and small vessel disease (white matter hyperintensities (WMH)) were measured in 1992-94. Global cognition (Modified Mini-Mental State (3MS) examination), mobility (gait speed (GS)) and mood (Center for Epidemiologic Studies Depression (CES-D) scale) were measured annually over 5 years and classified as clinical, subclinical or no disorders based on established values (3MS: 80 and 85 points; GS: 0.6 and 1.0 m/s; CES-D: 10 and 5 points). Analyses were adjusted for demographics, baseline status, education, diabetes, hypertension, ankle-arm index.

RESULTS: among those with no disorder in cognition, mobility and mood (N~=~619) in 1992-94, being in the lowest DSST quartile compared to the highest was associated with nearly twice the odds of developing 1+ clinical or subclinical disorders (N~=~413) during follow-up. Associations were stronger for incident clinical disorders in cognition (OR: 8.44, p~<~0.01) or mobility (OR: 9.09, p~<~0.05) than for mood (OR: 1.88, p~<~0.10). Results were similar after adjustment for WMH.

CONCLUSIONS: slower psychomotor speed may serve as a biomarker of risk of clinical disorders of cognition, mobility and mood. While in part attributable to vascular brain disease, other potentially modifiable contributors may be present. Further studying the causes of psychomotor slowing with ageing might provide novel insights into age-related brain disorders.

}, issn = {1468-2834}, doi = {10.1093/ageing/afw116}, author = {Rosano, Caterina and Perera, Subashan and Inzitari, Marco and Newman, Anne B and Longstreth, William T and Studenski, Stephanie} } @article {7161, title = {Gait Speed Predicts Incident Disability: A Pooled Analysis.}, journal = {J Gerontol A Biol Sci Med Sci}, volume = {71}, year = {2016}, month = {2016 Jan}, pages = {63-71}, abstract = {

BACKGROUND: Functional independence with aging is an important goal for individuals and society. Simple prognostic indicators can inform health promotion and care planning, but evidence is limited by heterogeneity in measures of function.

METHODS: We performed a pooled analysis of data from seven studies of 27,220 community-dwelling older adults aged 65 or older with baseline gait speed, followed for disability and mortality. Outcomes were incident inability or dependence on another person in bathing or dressing; and difficulty walking {\textonequarter} - {\textonehalf} mile or climbing 10 steps within 3 years.

RESULTS: Participants with faster baseline gait had lower rates of incident disability. In subgroups (defined by 0.2 m/s-wide intervals from <0.4 to >= 1.4 m/s) with increasingly greater gait speed, 3-year rates of bathing or dressing dependence trended from 10\% to 1\% in men, and from 15\% to 1\% in women, while mobility difficulty trended from 47\% to 4\% in men and 40\% to 6\% in women. The age-adjusted relative risk ratio per 0.1 m/s greater speed for bathing or dressing dependence in men was 0.68 (0.57-0.81) and in women: 0.74 (0.66-0.82); for mobility difficulty, men: 0.75 (0.68-0.82), women: 0.73 (0.67-0.80). Results were similar for combined disability and mortality. Effects were largely consistent across subgroups based on age, gender, race, body mass index, prior hospitalization, and selected chronic conditions. In the presence of multiple other risk factors for disability, gait speed significantly increased the area under the receiver operator characteristic curve.

CONCLUSION: In older adults, gait speed predicts 3 year incidence of bathing or dressing dependence, mobility difficulty, and a composite outcome of disability and mortality.

}, keywords = {Activities of Daily Living, Aged, Aged, 80 and over, Aging, Cohort Studies, Disability Evaluation, Disabled Persons, Female, Gait, Geriatric Assessment, Humans, Independent Living, Male, Mobility Limitation, Predictive Value of Tests, Prognosis, Psychomotor Performance, Risk Assessment, Risk Factors, ROC Curve, Survival Analysis, United States}, issn = {1758-535X}, doi = {10.1093/gerona/glv126}, author = {Perera, Subashan and Patel, Kushang V and Rosano, Caterina and Rubin, Susan M and Satterfield, Suzanne and Harris, Tamara and Ensrud, Kristine and Orwoll, Eric and Lee, Christine G and Chandler, Julie M and Newman, Anne B and Cauley, Jane A and Guralnik, Jack M and Ferrucci, Luigi and Studenski, Stephanie A} }