@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 {1334, title = {Slower gait, slower information processing and smaller prefrontal area in older adults.}, journal = {Age Ageing}, volume = {41}, year = {2012}, month = {2012 Jan}, pages = {58-64}, abstract = {

BACKGROUND: Slower gait in older adults is related to smaller volume of the prefrontal area (PFAv). The pathways underlying this association have not yet been explored. Understanding slowing gait could help improve function in older age. We examine whether the association between smaller PFAv and slower gait is explained by lower performance on numerous neuropsychological tests.

HYPOTHESIS: We hypothesise that slower information processing explains this association, while tests of language or memory will not.

METHODS: Data on brain imaging, neuropsychological tests (information processing speed, visuospatial attention, memory, language, mood) and time to walk 15 feet were obtained in 214 adults (73.3 years, 62\% women) free from stroke and dementia. Covariates included central (white matter hyperintensities, vision) and peripheral contributors of gait (vibration sense, muscle strength, arthritis, body mass index), demographics (age, race, gender, education), as well as markers of prevalent vascular diseases (cardiovascular disease, diabetes and ankle arm index).

RESULTS: In linear regression models, smaller PFAv was associated with slower time to walk independent of covariates. This association was no longer significant after adding information processing speed to the model. None of the other neuropsychological tests significantly attenuated this association.

CONCLUSIONS: We conclude that smaller PFAv may contribute to slower gait through slower information processing. Future longitudinal studies are warranted to examine the casual relationship between focal brain atrophy with slowing in information processing and gait.

}, keywords = {Affect, Aged, Aged, 80 and over, Aging, Attention, Body Mass Index, Cross-Sectional Studies, Female, Gait Disorders, Neurologic, Geriatric Assessment, Humans, Male, Memory, Mental Disorders, Mental Processes, Muscle Strength, Neuroimaging, Neuropsychological Tests, Prefrontal Cortex, Prevalence, Walking}, issn = {1468-2834}, doi = {10.1093/ageing/afr113}, author = {Rosano, Caterina and Studenski, Stephanie A and Aizenstein, Howard J and Boudreau, Robert M and Longstreth, William T and Newman, Anne B} } @article {1363, title = {Use of stance time variability for predicting mobility disability in community-dwelling older persons: a prospective study.}, journal = {J Geriatr Phys Ther}, volume = {35}, year = {2012}, month = {2012 Jul-Sep}, pages = {112-7}, abstract = {

BACKGROUND AND PURPOSE: Mobility disability is a serious and frequent adverse health outcome associated with aging. Early identification of individuals at risk for mobility disability is important if interventions to prevent disability are to be instituted. The objectives of this prospective study were to (1) determine the magnitude of stance time variability (STV) that discriminates individuals who currently have mobility disability (prevalent mobility disability) and (2) determine the magnitude of STV that predicts a new onset of mobility disability at 1 year (incident mobility disability).

METHODS: A total of 552 community-dwelling older adults were evaluated as part of the Cardiovascular Health Study, a longitudinal cohort study. Stance time, in milliseconds, was determined from 2 passes on a 4-m computerized walkway at self-selected walking speed, and STV was defined as the standard deviation from approximately 12 individual steps. Mobility disability was defined as self-reported difficulty walking a one-half mile. Receiver operating characteristic (ROC) curves were plotted to determine an optimal cutoff value for STV for prevalent and incident mobility disability, and the area under the receiver operating characteristic curve (AUC) was computed.

RESULTS: The optimal cutoff score for STV (maximizing sensitivity and specificity) for prevalent mobility disability was 0.037 seconds (sensitivity = 65\%, specificity = 65\%, AUC = 0.70) and for incident 1-year mobility disability was 0.034 seconds (sensitivity = 61\%, specificity = 60\%, AUC = 0.65). The use of likelihood ratios demonstrated a gradient of risk across values of STV, with mobility risk increasing as values of STV increased.

DISCUSSION AND CONCLUSION: Values of STV may be useful in identifying older adults with mobility disability and at risk for future disability. We recommend the more conservative estimate for identifying risk, STV = 0.034 seconds, which maximizes the sensitivity and minimizes false negatives. The relatively modest values on the validity indices could possibly be improved by increasing the reliability of the measurement of STV. Clinicians should interpret the cutoff values liberally and use STV in conjunction with other measures until further work is completed to validate STV as an indicator of mobility disability.

}, keywords = {Aged, Aged, 80 and over, Disability Evaluation, Female, Gait, Geriatric Assessment, Humans, Independent Living, Male, Mobility Limitation, Physical Therapy Modalities, Postural Balance, Prospective Studies, Reproducibility of Results}, issn = {2152-0895}, doi = {10.1519/JPT.0b013e318243e5f9}, author = {Brach, Jennifer S and Wert, David and VanSwearingen, Jessie M and Newman, Anne B and Studenski, Stephanie A} } @article {6107, title = {Long-term survival in adults 65 years and older with white matter hyperintensity: association with performance on the digit symbol substitution test.}, journal = {Psychosom Med}, volume = {75}, year = {2013}, month = {2013 Sep}, pages = {624-31}, abstract = {

OBJECTIVE: White matter hyperintensity (WMH) confers increased mortality risk in patients with cardiovascular diseases. However, little is known about differences in survival times among adults 65 years and older who have WMH and live in the community. To characterize the factors that may reduce mortality risk in the presence of WMH, measures of race, sex, apolipoprotein E4, neuroimaging, and cardiometabolic, physiological, and psychosocial characteristics were examined, with a particular focus on information processing as measured by the Digit Symbol Substitution Test (DSST).

METHODS: Cox proportional models were used to estimate mortality risks in a cohort of 3513 adults (74.8 years, 58\% women, 84\% white) with WMH (0-9 points), DSST (0-90 points), risk factor assessment in 1992 to 1994, and data on mortality and incident stroke in 2009 (median follow-up [range] = 14.2 [0.5-18.1] years).

RESULTS: WMH predicted a 48\% greater mortality risk (age-adjusted hazard ratio [HR; 95\% confidence interval {CI}] for WMH >3 points = 1.48 [1.35-1.62]). This association was attenuated after adjustment for DSST (HR [CI] = 1.38 [1.27-1.51]) or lacunar infarcts (HR [CI] = 1.37 [1.25,1.50]) but not after adjustment for other factors. The interaction between DSST and WMH was significant (p = .011). In fully adjusted models stratified by WMH of 3 or higher, participants with DSST greater than or equal to median had a 34\% lower mortality risk among those with WMH of 3 or higher (n = 532/1217) and a 28\% lower mortality risk among those with WMH lower than 3 (n = 1364/2296), compared with participants with DSST less than median (HR [95\% CI] = 0.66 [0.55-0.81] and 0.72 [0.62-0.83], respectively).

CONCLUSIONS: WMH is associated with increased long-term mortality risk in community-dwelling adults 65 years and older. The increased risk is attenuated for those with higher DSST. Assessment of cognitive function with DSST may improve risk stratification of individuals with WMH.

}, keywords = {Aged, Apolipoprotein E4, Biomarkers, Brain, Cardiovascular Diseases, Epidemiologic Methods, Female, Humans, Life Style, Magnetic Resonance Imaging, Male, Neuroimaging, Neuropsychological Tests, Reaction Time, Sex Factors, Stroke, Survivors}, issn = {1534-7796}, doi = {10.1097/PSY.0b013e31829c1df2}, author = {Rosano, Caterina and Chang, Yue-Fang and Kuller, Lewis H and Guralnik, Jack M and Studenski, Stephanie A and Aizenstein, Howard J and Gianaros, Peter J and Lopez, Oscar L and Longstreth, William T and Newman, Anne B} } @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} }