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Six-Minute Walk Test: A Meta-Analysis of Data From Apparently Healthy Elders

Bohannon, Richard W. PT, EdD, NCS, FAPTA, FAHA

Topics in Geriatric Rehabilitation: April-June 2007 - Volume 23 - Issue 2 - p 155–160
doi: 10.1097/01.TGR.0000270184.98402.ef
SPECIAL FEATURE
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Normative reference values are required if patient performance is to be put into perspective. This descriptive meta-analysis was undertaken to provide estimates of 6-minute walk test (6MWT) performance that could be used as normative reference values for individuals aged 60 years or older. Four bibliographic databases were searched online. Thirteen studies were identified that were usable. Meta-analysis demonstrated that reference values were best presented after grouping data by gender and age. Mean and 95% confidence intervals of 6MWT distances are presented separately for men and women in 3 age groups (60–69, 70–79. and 80–89 years). These consolidated values should provide a better estimate of normal performance than the individual studies from which they were derived.

Department of Physical Therapy, Neag School of Education, University of Connecticut, Storrs, Conn; and the Physical Therapy Consultants, West Hartford, Conn.

Corresponding author: Richard W. Bohannon, PT, EdD, NCS, FAPTA, FAHA, Physical Therapy Consultants, 130 Middlebrook Rd, West Hartford, CT 06119 (e-mail: ptconsultant@comcast.net).

The following individuals are gratefully recognized for their provision of clarification/elaboration regarding the data presented in their studies: Paul Enright, Ivan Bautmans, Elaine Cress, Geraldine Pellecchia, Claire Peel, Thierry Troosters, and VI Kalapotharakos.

THE 6-minute walk test (6MWT), a modification of the 12-minute walk test, was first described in 1985.1 Since that time, it has been used widely to quantify functional capacity and endurance.2 Although employed primarily in the evaluation of patients with pulmonary or cardiac pathology, the test has also been used with patients with other problems and with community-dwelling elders. Interpretation of an individual's performance on a test requires the availability of normative reference values.3 Normative values for the 6MWT have been published by several groups of investigators, but the procedures used and samples tested differ. Before minimum standards of performance for elders can be proffered, an examination and consolidation of available data should be conducted. The purpose of this meta-analysis, therefore, was to summarize and mathematically coalesce the results of studies describing the 6MWT performance of individuals aged at least 60 years.

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METHODS

Search strategy and selection criteria

The author conducted a search of the MEDLINE, Cumulative Index to Nursing and Allied Health, Science Citation Index, and EMBASE databases (1985–2005 [April]) to identify articles written in English that reported normative values for the 6MWT. The phrases “six minute walk” and “6 minute walk” were used in the searches. Apparently relevant articles were obtained and their reference lists were scanned for other potentially relevant articles. The titles and abstracts of articles identified by the searches were read and apparently relevant articles were obtained for further examination. Articles were retained for possible inclusion in the meta-analysis if they documented performance data for the 6MWT for apparently well individuals aged 60 years or older. Articles were excluded if subjects were clearly abnormal (eg, had heart disease or were frail), data could not be isolated for subjects 60 years or older, or data were known to duplicate (in whole or in part) those presented in another article.

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Data consolidation and analysis

The author abstracted included articles for subject sample, procedures (course, instructions, encouragement, trials, and measurement used), and performance data. Where possible, performance data were divided by decade (eg, 60–69 years) and gender. Authors were contacted as necessary and possible to assist with this breakdown when it was not provided outright. In studies reporting more than one value for 6MWT performance, those obtained at baseline or on the first trial were used.

The Statistical Package for the Social Sciences (SPSS, Version 11.0) was used to create a database suitable for the meta-analysis. The following variables were input from each relevant study: age range(s), gender, and the mean and standard deviation (SD) of the 6MWT distance (in meters). The variance (SD2) of the 6MWT distance was then computed, followed by calculation of the inverse of the variance. The syntax macros (meanes.sps and metaf.sps) provided by Wilson4 were used to analyze the homogeneity of the data obtained from different studies and to calculate overall means and 95% confidence intervals for 6MWT norms.

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RESULTS

Thirteen studies were found to include relevant data. For 12 of the studies, means and SDs for 6MWT times were either available or were made available by the authors.5–16 For one study, the mean and SD for 6MWT times were derived from scatterplots made available by the authors.17

Study specifics are reported in Table 1. All studies employed convenience samples. Most (9) of the studies involved North American subjects, but 4 studies involved subjects from Europe. Procedural variables were often unreported. The courses described varied considerably. Corridors (hallways) of various lengths (50 ft = 82.3 m) were used most often, but several studies used circular courses. Instructions were generally compatible with one another, and encouragement, when described, was standardized. When reported, the number of trials varied from 1 to 6. The measurement used was often not stated, but when designated was often the first or only trial, the second trial, or the best trial.

Table 1

Table 1

Table 1

Table 1

The mean number of meters that subjects could walk in 6 minutes ranged from 310 for 80- to 89-year-old women12 to 671 for 60- to 69-year-old men.16Table 2 presents the results of most of the meta-analysis. The analysis of all data (4809 subjects), without reference to age or gender, revealed the data to be homogeneous (Q = 76.8, P = .097) but not strongly. Therefore, data were compared between men and women. Not all studies presented separate 6MWT data for men and women, but an analysis of those that did, demonstrated a lack of homogeneity (Q = 5.79, P = .0161) between man and woman samples. Improved homogeneity was shown when analysis focused separately on men (n = 1534, Q = 33.5, P = .299) and women (n = 3212, Q = 37.3, P = .138). An analysis comparing age groups (60–69, 70–79, and 80–89 years) within each gender group found that the age groups did not provide homogeneous data for men (Q = 8.48, P = .0144) or women (Q = 9.50, P = .0087). Analyses of 6MWT data for the 3 age groups of each gender demonstrated improved homogeneity (Q = 4.1–8.0, P = .516–.689). Consequently, the weighted means (and confidence intervals) from these subgroup analyses are probably most suitable for judging the normalcy of individual 6MWTs.

Table 2

Table 2

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DISCUSSION

The 6MWT is widely used as an indicator of functional aerobic capacity.2 Although several publications have presented normative data, the norms were not obtained from multiple geographic locations and samples. In undertaking this meta-analysis, the author hoped to consolidate data from diverse studies and generate 6MWT standards against which individual patient's performance could be compared. Normative standards are provided for the entire sample, but values for men and women in 60–69, 70–79, and 80–89 years' age groups are probably most important if the intent is to judge the normalcy of performance of individuals aged between 60 and 89 years.

Granting that the normative values presented herein account for age and gender, which have been identified by the American Thoracic Society as determinants of 6MWT performance,18 other determinants such as height could not be addressed in subgroup analysis. Procedures employed in the included studies varied considerably, with many being inconsistent with the recommendations of the American Thoracic Society guidelines; that is, use of a 30-m long course in a corridor, provision of standardized instructions/feedback, and recording of the time of a single trial after no more than one practice trial. Ideally, it would be best to have norms that were (1) gathered from a large random sample of apparently healthy individuals residing in different communities and (2) obtained using standardized procedures such as those recommended by the American Thoracic Society. In the absence of such norms, those presented herein should provide a reasonable estimate for clinical comparisons.

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REFERENCES

1. Guyatt GH, Sullivan MJ, Thompson PJ, et al. The 6-minute walk: a new measure of exercise capacity in patients with chronic heart failure. Can Med Assoc J. 1985;132:921–923.
2. Sadaria KS, Bohannon RW. The 6-minute walk test: a brief review of literature. Clin Exerc Physiol. 2001;3:127–132.
3. Rothstein JM, Echternach JL. Primer on Measurement: An Introductory Guide to Measurement Issues. Alexandria, Va: American Physical Therapy Association; 1993:46–54.
4. Wilson DB. Meta-analysis stuff. Available at:
5. Bautmans I, Lambert M, Mets T. The six-minute walk test in community dwelling elderly: influence of health status. BMC Geriatr. 2004;4:6.
6. Cress ME, Petrella JK, Moore TL, Schenkman ML. Continuous-Scale Physical Functional Performance Test: validity, reliability, and sensitivity of data for the short version. Phys Ther. 2005;85:323–335.
7. Gibbons WJ, Fruchter N, Sloan S, Levy RD. Reference values for a multiple repetition 6-minute walk test in healthy adults older than 20 years. J Cardiopulm Rehabil. 2001;21:87–93.
8. Harada ND, Chiu V, Stewart AL. Mobility-related function in older adults: assessment with a 6-minute walk test. Arch Phys Med Rehabil. 1999;80:837–841.
9. Kalapotharakos VI, Michalopoulos M, Tokmakidis SP, Godolias G, Strmpakos N, Karteroliotis K. Effects of a resistance exercise programme on the performance of inactive older adults. Int J Ther Rehabil. 2004;11:318–323.
10. Kervio G, Carre F, Ville NS. Reliability and intensity of the six-minute walk test in healthy elderly subjects. Med Sci Sports Exerc. 2003;35:169–174.
11. Lusardi MM, Pellecchia GL, Schulman M. Functional performance in community living older adults. J Geriatr Phys Ther. 2003;26(3):14–22.
12. Peel C, Ballard D. Reproducibility of the 6-minute-walk test in older women. J Aging Phys Activ. 2001;9:184–193.
13. Peterson MJ, Crowley GM, Sullivan RJ, Morey MC. Physical function in sedentary and exercising older veterans as compared to national norms. J Rehabil Res Dev. 2004;41:653–658.
14. Rikli RE, Jones CJ. Functional fitness normative scores for community-residing older adults, ages 60–94. J Aging Phys Activ. 1999;7:162–181.
15. Steffen TM, Hacker TA, Mollinger L. Age- and gender-related test performance in community-dwelling elderly people: Six-Minute Walk Test, Berg Balance Scale, Timed Up & Go Test, and gait speeds. Phys Ther. 2002;82:128–137.
16. Troosters T, Gosselink R, Decramer M. Six minute walking distance in healthy elderly subjects. Eur Respir J. 1999;14:270–274.
17. Enright PL, Sherrill DL. Reference equations for the six-minute walk in healthy adults. Am Rev Respir Crit Care Med. 1998;158:1384–1387.
18. American Thoracic Society. ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med. 2002;166:111–117.
Keywords:

aging; measurement; normative reference values; 6-minute walk test

© 2007 Lippincott Williams & Wilkins, Inc.