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Gait speed was associated with survival in older adults
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Walking speed associated with survival in older adults
'For many elderly folks who walk slowly, hitting the treadmill at the gym to improve their fitness level isn't the solution. "We need to do more to figure out what slows gait speed," Sorond acknowledges. "It's a complex process."
On the other hand, if you're just starting to slow down a bit and don't have major medical problems, getting that exercise may be the key to a longer life, Sorond contends. "I'm sure a 70-year-old marathoner has a faster gait than the average person, and we know that good physical fitness is an important predictor of life expectancy." '
www.physorg.com
January 4, 2011
In an analysis that included data from 9 studies, having higher measures of walking speed among older adults was associated with increased length of survival, according to a study in the January 5 issue of JAMA.
"Remaining years of life vary widely in older adults, and physicians should consider life expectancy when assessing goals of care and treatment plans. However, life expectancy based on age and sex alone provides limited information because survival is also influenced by health and functional abilities," according to background information in the article. There are currently no well-established approaches to predicting life expectancy that incorporate health and function. Gait speed, or walking speed, has been recommended as a potentially useful clinical indicator of well-being among older adults.
Stephanie Studenski, M.D., M.P.H., of the University of Pittsburgh, and colleagues conducted a study to assess the association of gait speed with survival in older adults and to determine the degree to which gait speed explains variability in survival after accounting for age and sex. The study included a pooled analysis of 9 participating studies (collected between 1986 and 2000), using individual data from 34,485 community-dwelling adults age 65 years or older with walking speed data available at the beginning of the study, followed up for 6 to 21 years. Participants had an average age of 73.5 years; 59.6 percent were women; and 79.8 percent were white. Gait speed was calculated for each participant using distance in meters and time in seconds. All studies used instructions to walk at usual pace and from a standing start. The walk distance varied from 8 feet to 6 meters. The average gait speed of the participants was 0.92 meters (3 feet) per second.
During the course of the study, there were 17,528 deaths. The overall 5-year survival rate was 84.8 percent; the 10-year survival rate was 59.7 percent. The researchers found that gait speed was associated with differences in the probability of survival at all ages in both sexes, but was especially informative after age 75 years. At this age, predicted 10-year survival across the range of gait speeds ranged from 19 percent to 87 percent in men and from 35 percent to 91 percent in women.
"Predicted years of remaining life for each sex and age increased as gait speed increased, with a gait speed of about 0.8 meters [2.6 feet]/second at the median [midpoint] life expectancy at most ages for both sexes. Gait speeds of 1.0 meter [3.3 feet]/second or higher consistently demonstrated survival that was longer than expected by age and sex alone. In this older adult population the relationship of gait speed with remaining years of life was consistent across age groups, but the absolute number of expected remaining years of life was larger at younger ages," the authors write.
The researchers also found that predicted survival based on age, sex, and gait speed was as accurate as predictions 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.
The authors suggest there are several reasons why gait speed may predict survival. "Walking requires energy, movement control, and support and places demands on multiple organ systems, including the heart, lungs, circulatory, nervous, and musculoskeletal systems. Slowing gait may reflect both damaged systems and a high energy cost of walking."
The researchers write that there are a number of ways gait speed might be used clinically, including helping to identify older adults with a high probability of living for 5 or 10 more years, who may be appropriate targets for preventive interventions that require years for benefit. Gait speed might be used to identify older adults with increased risk of early mortality, perhaps those with gait speeds slower than 0.6 meter (2 feet)/second. "In these patients, further examination is targeted at potentially modifiable risks to health and survival." Also, gait speed might be monitored over time, with a decline indicating a new health problem that requires evaluation.
"The data provided herein are intended to aid clinicians, investigators, and health system planners who seek simple indicators of health and survival in older adults. Gait speed has potential to be implemented in practice, using a stop watch and a 4-meter [13 feet] course. From a standing start, individuals are instructed to walk at their usual pace, as if they were walking down the street, and given no further encouragement or instructions. The data in this article can be used to help interpret the results. Gait speed may be a simple and accessible indicator of the health of the older person," the authors conclude.
Gait Speed Associated With Survival in Older Adults
doctorslounge.com
Last Updated: January 04, 2011.
In older adults, gait speed appears to be related to survival, according to research published in the Jan. 5 issue of the Journal of the American Medical Association.
TUESDAY, Jan. 4 (HealthDay News) -- In older adults, gait speed appears to be related to survival, according to research published in the Jan. 5 issue of the Journal of the American Medical Association.
Stephanie Studenski, M.D., M.P.H., of the University of Pittsburgh, and colleagues analyzed nine cohort studies that included gait speed data and involved 34,485 community-dwelling adults aged 65 or older. Participants, with a mean age of 73.5, were followed for six to 21 years.
The researchers found gait speed to be associated with survival in all studies (pooled hazard ratio per 0.1 m/s, 0.88), with survival increasing significantly with 0.1-m increments. For 75-year-old adults, the 10-year survival prediction ranged 19 to 87 percent for men and 35 to 91 percent for women across the range of gait speeds. Predicted survival based on gait speed, age, and sex was as accurate as that predicted based on sex, age, self-reported function, and use of mobility aids or that predicted based on sex, age, chronic conditions, blood pressure, smoking history, body mass index, and hospitalization.
"Gait speed has potential to be implemented in practice, using a stop watch and a 4-m course. From a standing start, individuals are instructed to walk at their usual pace, as if they were walking down the street, and given no further encouragement or instructions. The data in this article can be used to help interpret the results," the authors write.
Several authors disclosed financial relationships with pharmaceutical companies, including Merck, which provided grant support for the research.
www.boston.com
A few years ago, I noticed my mom starting to walk, well, like an old lady -- slow and hunched over a bit. Being the blunt daughter that I am, I told her so. She started going to the gym more and taking daily yoga classes, and now the 64-year-old walks like she's 44.
Turns out, your walking speed may predict how long you'll live. That's according to a new study published Tuesday in the Journal of the American Medical Association.
The University of Pittsburgh researchers looked at data from nine studies involving nearly 35,000 seniors and found that only 19 percent of the slowest walking 75-year-old men lived for 10 more years compared to 87 percent of the fastest walking ones. Only 35 percent of the slowest walking 75-year-old women made it to their 85th birthday compared to 91 percent of the fastest walkers.
"This paper is a monumental effort in data analysis to come up with exact numbers and predictors in terms of the relationship between gait speed and survival," says Dr. Farzaneh Sorond, a stroke neurologist at Brigham and Women's hospital who studies gait speed in the elderly but wasn't involved in this study.
While Sorond says she typically observes how her patients walk during her assessments, she never measured their speed. "With this new information, I'd think seriously about implementing gait speed as part of a routine assessment."
The researchers found that the usual walking pace of those over 65 varied from less than 1.3 feet per second over 13 feet -- which carried the highest death risk -- to more than 4.6 feet per second, which was associated with the lowest risk. Sorond says she can use this information to advise her patients.
"If they fall into the fast super-performer group, I can tell them they have a pretty good chance of outliving their peers," she says. On the flip side, those who walk the slowest might need more aggressive interventions to treat underlying medical conditions that cause gait to slacken through the years.
But therein lies the rub. Perhaps the increased death risk comes from serious medical conditions -- like Parkinson's, multiple organ failure, and severe vascular disease -- all of which can slow walking speed and, in their own right, lead to shorter lives.
That's true, acknowledge the study researchers, but that's also the point. They write that gait speed could be considered a reliable way to access vitality "because it integrates known and unrecognized disturbances in multiple organ systems."
For many elderly folks who walk slowly, hitting the treadmill at the gym to improve their fitness level isn't the solution. "We need to do more to figure out what slows gait speed," Sorond acknowledges. "It's a complex process."
On the other hand, if you're just starting to slow down a bit and don't have major medical problems, getting that exercise may be the key to a longer life, Sorond contends. "I'm sure a 70-year-old marathoner has a faster gait than the average person, and we know that good physical fitness is an important predictor of life expectancy."
Editorial
Role of Gait Speed in the Assessment of Older Patients
JAMA. 2011;305(1):93-94. doi: 10.1001/jama.2010.1970
Matteo Cesari, MD, PhD
Author Affiliations: Area di Geriatria, Universita Campus Bio-Medico, Roma, Italy.
Corresponding Author: Matteo Cesari, MD, PhD, Area di Geriatria, Universita Campus Bio-Medico, Via Alvaro del Portillo 200, 00128 Roma, Italy (macesari@gmail.com).
Over the last 3 decades, a large and increasing amount of evidence has documented the importance of physical function in elderly individuals, both as a crucial component of clinical assessment as well as a specific outcome for interventions.1 However, the evaluation of physical function is still not considered as relevant as that of other clinical or biochemical parameters. Insufficient time, inadequate space, and the need for special equipment are some of the obstacles to the routine assessment of physical function in the geriatric clinical settings.2 To overcome these limitations, gait speed has repeatedly and increasingly been proposed as an unique measure of physical performance and as a potential screening tool,3 ,4 but adoption has remained inconsistent.
In this issue of JAMA, the study by Studenski et al5 fills an important research gap and paves the way to a broader adoption of gait speed assessment. Their findings from a pooled analysis of 9 major cohort studies confirm gait speed as a predictor of mortality in older persons3,4 ,6 and also provide the statistical foundations to estimate expected survival at different ages based only on gait speed. Several barriers limiting the clinical use of physical performance measures might thus be considered overcome. First, the study establishes the validity of a test readily adoptable to clinical use that, differently from other functional assessment tools, is inexpensive, objective, and easy to interpret. Second, the study standardizes the methods to assess gait speed to the 4-meter-long track starting from a still, standing position. This is not a trivial accomplishment because gait speed has often been measured testing individuals over tracks of different lengths (eg, 8 ft or 4 or 6 m), sometimes after exclusion of the initial acceleration time, leading to difficulties in interpretation, comparability, or both. Third, the study by Studenski et al5 assesses survival of older persons associated with various gait speed results.
The increase in life expectancy at a population level has further highlighted the heterogeneity of individuals, making it increasingly difficult to distinguish merely old (chronologically aged) from geriatric (biologically aged) patients. This very ability to screen frail geriatric patients vs old individuals is an urgent matter in geriatrics but increasingly urgent in other specialties. For example, oncologists seek objective methods to identify patients eligible for standard and more aggressive interventions because they are chronologically, but not biologically, old.7 Also, cardiac surgeons have proposed gait speed as a means to identify which older patients undergoing surgery may be at increased risk for adverse outcomes.8 ,9 Assessment of gait speed may serve as a single-item screening tool to determine which patients need a geriatric multidisciplinary approach to care. At the same time, gait speed should be regarded as an important component of the comprehensive geriatric assessment, provided it facilitates clinical decisions on the basis of a "hard" outcome such as life expectancy.
The study by Studenski et al5 may also be of interest for investigators involved in clinical research on aging. Researchers and clinicians seek results that are clinically, not just statistically, significant. Because of the established association of gait speed with survival, it could be used as a surrogate for survival outcomes in clinical trials of older persons.
Gait speed should not be regarded solely as a measure of lower extremity function. Gait speed has been associated with clinical (eg, comorbidities)10 as well as subclinical conditions (eg, atherosclerosis11 or inflammatory status12) and is able to predict several health-related events even apparently unrelated to physical function (eg, cognitive impairment, hospitalization, institutionalization).3 ,4 Gait speed may serve as a marker of physiological reserve and potentially could quantify overall health status. Indeed, a close relationship between mobility performance and the aging process has been documented in humans3 and animals.13,14 ,15 This convergence may indicate the existence of shared pathophysiological mechanisms; thus, at some point, gait speed may be considered a new "vital sign," specifically sensitive for older persons.
Results by Studenski et al5 showed that gait speed had only a statistically fair accuracy for predicting survival for gait speed (pooled area under the receiver operator characteristic curve equal to 0.717 and 0.737 for 5-year and 10-year survival, respectively). However, very similar results were also reported from models testing the overall predictive value of multiple clinical data (ie, prevalent diseases, body mass index, systolic blood pressure, and history of prior hospitalizations). Therefore, although the gait speed assessment may present some limitations in accurately estimating the expected survival, it still matches the predictive value obtained from an extensive and more complex clinical evaluation. Moreover, it is also noteworthy that overall mortality is a composite outcome, subject to a wide range of unmeasurable confounders, and thus may limit the ability to identify a highly accurate predictive model.
It is possible that the study sample considered in the analyses by Studenski et al5 may not be representative of the general older population, limiting the direct applicability of the findings. Nevertheless, the study illustrates the importance of transforming gait speed into a clinically meaningful parameter and demonstrating its predictive ability above and beyond classical comorbidities. Clinical practice is based on assumptions and, thus, never perfect. In this context, the categorization of a continuous variable (and this study greatly facilitates this task) represents the easiest way to quickly identify those at risk.
The simplicity of the gait speed assessment does not exclude possible issues from its routine implementation in clinical settings, especially in primary care practice. Functional limitations, cognitive impairment, hearing or visual problems, and balance or postural disorders may render the test more time-consuming than expected. Furthermore, clinicians will be required to spend some additional time explaining the significance of the novel assessment to their patients and relatives. However, the logistical, methodological, and conceptual familiarization of the clinical staff with the test might speed up its assessment over time. Moreover, the gait speed assessment does not need to be performed in all older patients because it is not as informative when functional disability is already present.
The prevention of physical disability is a primary goal of geriatric medicine and a major public health priority. In the scenario shaped by the present study, future analyses should consider physical disability as a primary outcome, expanding and completing the understanding of the role and relevance of gait speed as a means to identify patients at risk for functional decline. This task requires a consensus around the definitions of disability to be most widely generalizable.
Because no evidence definitively supports the hypothesis that gait speed improvements are associated with better health-related outcomes, gait speed should not be considered as a primary target for interventions at this time. It represents a global marker of health status, and an optimal secondary and complementary outcome to support research findings, clinical decisions, or both aimed at modifying more pragmatic end points.
In conclusion, assessing gait speed in older persons is likely to be a useful research tool and may have a clinical role. Future research will be needed to determine whether gait speed has the potential to change the way in which a patient is defined as geriatric.
Gait Speed and Survival in Older Adults
JAMA Jan 2011
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.
Remaining years of life vary widely in older adults, and physicians should consider life expectancy when assessing goals of care and treatment plans.1 However, life expectancy based on age and sex alone provides limited information because survival is also influenced by health and functional abilities.2 There are currently no well-established approaches to predicting life expectancy that incorporate health and function, although several models have been developed from individual data sources.3 ,4,5 Gait speed, also often termed walking speed, has been shown to be associated with survival among older adults in individual epidemiological cohort studies6,7 ,8,9 ,10,11 ,12 and has been shown to reflect health and functional status.13 Gait speed has been recommended as a potentially useful clinical indicator of well-being among the older adults.14 The purpose of this study is to evaluate the association of gait speed with survival in older adults and to determine the degree to which gait speed explains variability in survival after accounting for age and sex.
COMMENT
Gait speed, age, and sex may offer the clinician tools for assessing expected survival to contribute to tailoring goals of care in older adults. The accuracy of predictions based on these 3 factors appears to be approximately similar to more complex models involving multiple other health-related factors, or for age, sex, use of mobility aids, and functional status. Gait speed might help refine survival estimates in clinical practice or research because it is simple and informative.
Why would gait speed predict survival? Walking requires energy, movement control, and support and places demands on multiple organ systems, including the heart, lungs, circulatory, nervous, and musculoskeletal systems. Slowing gait may reflect both damaged systems and a high-energy cost of walking.13 ,39,40 ,41,42 ,43,44 ,45,46 ,47,48 ,49,50 ,51,52 ,53,54 Gait speed could be considered a simple and accessible summary indicator of vitality because it integrates known and unrecognized disturbances in multiple organ systems, many of which affect survival. In addition, decreasing mobility may induce a vicious cycle of reduced physical activity and deconditioning that has a direct effect on health and survival.6
The association between gait speed and survival is known.6 ,7,9 ,10,11 ,12,55 ,56 Prior analyses used single cohorts and presented results as relative rather than absolute risk, as done herein. Similarly, mortality prediction models have been developed.3 ,4,5 ,57,58 ,59,60 Some models use self-reported information but others also include physiological or performance data, for a total of 4 to more than 10 predictive factors. Only a few models assess overall predictive capacity using C statistics; the reported values are in the range found in the present study (published area under the curve range, 0.66-0.8261 vs this study, 0.717 and 0.737).
The strengths of this study are the very large sample of individual participant data from multiple diverse populations of community-dwelling elders who were followed up for many years and use of consistent measures of performance and outcome. We provide survival estimates for a broad range of gait speeds and calculate absolute rates and median years of survival. Compared with prior studies that were too small to assess potential effect modification by age, sex, race/ethnicity, and other subgroups, we were able to assess multiple subgroup effects with substantial power. This study has the limitations of observational research; it cannot establish causal relationships and is vulnerable to various forms of healthy volunteer bias. The participating study cohorts, while large and diverse, do not represent the universe of possible data. Our survival estimates should be validated in additional data sets. Only 1 of the 9 studies was based in clinical practice,21 and advanced dementia is rare in populations who are competent to consent for research. However, median years of survival in this study resemble estimates for US adults across the sex and age range assessed.62 We were unable to assess the association of physical activity with survival in pooled analyses because measures of activity were highly variable across studies. Also, participants in these studies had no prior knowledge about the meaning of walking speed. In clinical use, participants might walk differently if they are aware of the implications of the results. Although this study provides information on survival, further work is needed to examine associations of other important pooled outcomes such as disability and health care use and to examine effects in populations more completely based in clinical practice.
Because gait speed can be assessed by nonprofessional staff using a 4-m walkway and a stopwatch,21 it is relatively simple to measure compared with many medical assessments. Nevertheless, methodological issues such as distance and verbal instructions remain.63,64 Self-report is an alternative to gait speed for reflecting function. However, significant challenges remain in the use of self-report as well, such as choice of items and reliability, some of which can be addressed by emerging techniques such as computer adaptive testing based on item-response theory.65 The results found herein suggest that gait speed appears to be especially informative in older persons who report either no functional limitations or only difficulty with instrumental ADLs and may be less helpful for older adults who already report dependence in basic ADLs. The research studies analyzed herein used trained staff to measure gait speed. Staff in clinical settings would need initial training and may produce more variable results. Long-distance walks have become accepted in some medical fields and may contribute information beyond short walks.66 ,67,68 However, the longer distance and time to perform the test may limit feasibility in many clinical settings. Although the sample size of very slow walkers was small, our data suggest that there may be a subpopulation who walk very slowly but survive for long periods. It would be valuable to further characterize this subgroup.
Although the gait speed-survival relationship seems continuous across the entire range, cut points may help interpretation. Several authors have proposed that gait speeds faster than 1.0 m/s suggest healthier aging while gait speeds slower than 0.6 m/s increase the likelihood of poor health and function.7,21 Others propose one cutoff around 0.8 m/s.13 In our data, predicted life expectancy at the median for age and sex occurs at about 0.8 m/s; faster gait speeds predict life expectancy beyond the median. Perhaps a gait speed faster than 1.0 m/s suggests better than average life expectancy and above 1.2 m/s suggests exceptional life expectancy, but additional research will be necessary to determine this relationship.
How might gait speed be used clinically? First, gait speed might help identify older adults with a high probability of living for 5 or 10 more years, who may be appropriate targets for preventive interventions that require years for benefit. Second, gait speed might be used to identify older adults with increased risk of early mortality, perhaps those with gait speeds slower than 0.6 m/s. In these patients, further examination is targeted at potentially modifiable risks to health and survival. A recommended evaluation and management of slow walking includes cardiopulmonary, neurological and musculoskeletal systems.6 ,18 Third, gait speed might promote communication. Primary clinicians might characterize an older adult as likely to be in poor health and function because the gait speed is 0.5 m/s. In research manuscripts, baseline gait speed might help to characterize the overall health of older research participants. Fourth, gait speed might be monitored over time, with a decline indicating a new health problem that requires evaluation. Fifth, gait speed might be used to stratify risks from surgery or chemotherapy. Finally, medical and behavioral interventions might be assessed for their effect on gait speed in clinical trials. Such true experiments could then evaluate causal pathways to determine whether interventions that improve gait speed lead to improvements in function, health, and longevity.
The data provided herein are intended to aid clinicians, investigators, and health system planners who seek simple indicators of health and survival in older adults. Gait speed has potential to be implemented in practice, using a stop watch and a 4-m course. From a standing start, individuals are instructed to walk at their usual pace, as if they were walking down the street, and given no further encouragement or instructions. The data in this article can be used to help interpret the results. Gait speed may be a simple and accessible indicator of the health of the older person.
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