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SPECIAL SECTION |
Address correspondence to Marco Pahor, MD, Department of Aging and Geriatric Research, College of Medicine, University of Florida, 1329 SW 16th St., Rm. 5161, Gainesville, FL 32608. E-mail: mpahor{at}ufl.edu
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Methods. A total of 424 sedentary persons at risk for disability (ages 70–89 years) were randomized to a moderate-intensity PA intervention or a successful aging (SA) health education intervention and were followed for an average of 1.2 years.
Results. The mean baseline SPPB score on a scale of 0–12, with 12 corresponding to highest performance, was 7.5. At 6 and 12 months, the PA versus SA group adjusted SPPB (± standard error) scores were 8.7 ± 0.1 versus 8.0 ± 0.1, and 8.5 ± 0.1 versus 7.9 ± 0.2, respectively (p <.001). The 400-meter walking speed was also significantly improved in the PA group. The PA group had a lower incidence of major mobility disability defined as incapacity to complete a 400-meter walk (hazard ratio = 0.71, 95% confidence interval = 0.44–1.20).
Conclusions. A structured PA intervention improved the SPPB score and other measures of physical performance. An intervention that improves the SPPB performance may also offer benefit on more distal health outcomes, such as mobility disability.
Randomized controlled trials in older persons have shown that structured physical activity (PA) interventions, including resistance and endurance exercises, improve a variety of physical performance measures, such as walking speed, stair-climb speed, balance, and chair stands (13–24). Additional intervention studies have shown that PA can result in improved changes in the SPPB score (25,26). The latter studies have been limited by relatively small sample size and short duration of follow-up. To our knowledge, conclusive evidence from large, multicenter, randomized controlled trials that a structured PA intervention can improve the SPPB score is still lacking. To address this gap in knowledge, we report the main results of the Lifestyle Interventions and Independence for Elders pilot (LIFE-P) study. An intervention that improves performance on the SPPB score may also offer benefit on more distal health outcomes, such as major mobility disability (7).
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The study was conducted at four field centers (Cooper Institute, Stanford University, University of Pittsburgh, and Wake Forest University [WFU]). Data management and statistical analyses were performed at WFU, and the Administrative Coordinating Center was first at WFU, and later moved to the University of Florida. The study was approved by the local institutional review boards. A data safety monitoring board monitored safety and the conduct of the trial; participants gave written informed consent. The protocol is consistent with the principles of the Declaration of Helsinki and is registered at www.ClinicalTrials.gov (registration # NCT00116194).
Participants
The design of the trial has been described in detail elsewhere (27). Briefly, inclusion criteria were having an age of 70 to 89 years, having a sedentary lifestyle (<20 min per week spent in structured PA during the past month), being able to walk 400 meters within 15 minutes without sitting and without use of any assistive device, having a SPPB score 
9 (on a scale of 0 to 12, as described below), having completed a behavioral run-in related to logging health behavior, given informed consent, living in the study area, and not planning to move for at least 9 months. Participants were ineligible if they had severe heart failure, uncontrolled angina, severe pulmonary disease, chest pain or severe shortness of breath during the 400-meter walk test, severe arthritis, cancer requiring treatment in the past 3 years, Parkinson's disease, other severe illness that may interfere with physical activity, illness with life expectancy of less than 12 months, or a Mini-Mental State Examination score <21 (28). Temporary exclusion criteria were acute myocardial infarction, deep venous thrombosis, pulmonary embolism, major arrhythmias, or stroke within 6 months, recent major surgery, uncontrolled hypertension, uncontrolled diabetes, and ongoing lower extremity physical therapy.
Recruitment relied primarily on mass mailing, community outreach, and media advertising. Participants who were eligible after an initial phone screening were invited for clinic visits, during which they signed the informed consent form and completed a personal interview, the SPPB, a physical exam, an electrocardiogram, and a 400-meter walk test. Eligible participants received detailed instructions for a 1-week to 2-week behavioral run-in, during which they were asked to self-monitor specific behaviors and to complete forms related to these behaviors. Participants who successfully completed the behavioral run-in received additional baseline assessments and were randomized to the study interventions via a web-based system. Of the 3141 persons who were initially screened by phone, a total of 424 (13.5%) were ultimately randomized (Figure 1). The recruitment goal was 400 participants (70% women, 25% minorities, and 40% with SPPB score 7).
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3/week) were started. The subsequent maintenance phase consisted of the home-based intervention, optional once-to-twice-per-week center-based sessions, and monthly telephone contacts. The PA intervention included group-based behavioral counseling sessions (1/week for the first 10 weeks) that focused on PA participation and disability prevention, and on encouraging participants to increase all forms of PA. The PA intervention focused on walking as the primary mode of exercise. The goal was walking for at least 150 minutes over the course of the week (29). Each session was preceded by a brief warm-up and followed by a brief cool-down period. To complement the walking program, participants completed lower extremity strengthening exercises, followed by lower extremity stretching exercises. Balance training was introduced during the adoption phase. The intensity of training was gradually increased over the first 2–3 weeks. Perceived exertion assessed by the Borg scale (30) was used to regulate the intensity of exercise; moderate intensity exercise was promoted (31,32). Participants were asked to walk at a target intensity of 13 (somewhat hard), and they were discouraged from exercising at levels 15 (hard) or 11 (fairly light). Strengthening exercises were performed at a perceived exertion of 15–16.
Successful Aging Intervention
An SA health education intervention was used as the active control and was designed to provide attention and health education. Participants met in small groups weekly for the first 26 weeks and then monthly. Sessions included health topics relevant to older adults such as nutrition, medications, foot care, and recommended preventive services at different ages. Basic educational information related to physical activity was provided. At the end of each session, a short instructor-led intervention (5–10 min) of gentle upper extremity stretching exercises was delivered. Telephone calls were made after each missed session to encourage regular participation, and participants received a monthly newsletter.
Measurements
Participants were enrolled between April 2004 and February 2005. Follow-up was planned for 12 to18 months, depending on the date of randomization, and included semiannual clinic visits for data collection. The 18-month visit was performed only in participants who were recruited early in the study, primarily to assess the persistence of major mobility disability (data are not reported here). To ensure blinding, participants were instructed not to discuss their intervention during the assessments, and the assessments were conducted by blinded staff members at locations other than the intervention sites.
Baseline assessments included a personal interview, anthropometric measures, physical exam, electrocardiogram, and a physician evaluation. The Mini-Mental State Examination test was used for cognitive screening (28). Prevalence of clinical conditions was determined using self-reported physician-diagnosed disease information. The Community Healthy Activities Model Program for Seniors (CHAMPS) questionnaire was used to assess self-reported physical activity (33).
Outcomes
The SPPB score is based on timed measures of standing balance, walking speed, and ability to rise from a chair (7,9). For the balance test, participants were asked to maintain their feet in side-by-side, semitandem (heel of one foot beside the big toe of the other foot), and tandem (heel of one foot in front and touching the other foot) positions for 10 seconds each. Walking speed was assessed by asking participants to walk at their usual pace over a 4-meter course. Two walk times were recorded, and the faster of the two was used to compute the walking test score. For the chair test, participants were asked to stand up from a sitting position with their arms folded across the chest. If participants were able to perform this task, they were asked to stand up and sit down five times as quickly as possible, and the time to perform the test was recorded.
Each of the three performance measures was assigned a score ranging from 0 to 4, with 4 indicating the highest level of performance and 0 the inability to complete the test. A summary score (range 0–12) was subsequently calculated by adding the three scores. For the test of balance, participants were assigned the following scores: 1 if they could only hold a side-by-side standing position for 10 seconds; 2 if they could hold a semitandem position for 10 seconds, but were unable to hold a full-tandem position for more than 2 seconds; 3 if they could stand in a full-tandem position for 3 to 9 seconds; and 4 if they could stand in a full-tandem position for 10 seconds.
Four categories were computed for walking speed and chair stands, according to cut-points based on quartiles of the time to perform each task established by the Established Populations for Epidemiologic Studies of the Elderly (EPESE) (6). Gait speed was scored as follows: <0.41 m/s = 1; 0.41–0.57 m/s = 2; 0.58–0.75 m/s = 3; >0.75 m/s = 4. The time required to perform five chair stands was scored as follows: >16.6 s = 1; 13.7–16.6 s = 2; 11.2–13.6 s = 3; <11.2 s = 4.
For the 400-meter walk, participants were asked to walk 10 laps of a 20-meter course at their usual pace. Participants were allowed to stop and rest if necessary, but without sitting. Major mobility disability was defined as the inability to complete the 400-meter walk test within 15 minutes. If the 400-meter walk test could not be assessed, the outcome was adjudicated by a committee of masked investigators who used information from self-reports and proxy reports, the result of the 4-meter walk test, and medical records. Deaths were verified from proxies, death certificates, and medical records.
Statistical Analysis and Sample Size Considerations
For comparing the SPPB scores at the 6-month or 12-month visits, the study had 80% power to detect a mean difference between intervention groups of 0.52 and 90% power to detect a mean difference of 0.60, assuming a two-sided 0.05 significance level and testing hypotheses as contrasts using repeated measures analysis of covariance. A 0.5 difference in SPPB score is considered a meaningful change (34).
All comparisons between intervention groups were performed with participants grouped according to randomization assignment. Comparisons of discrete baseline characteristics (e.g., gender, race) were performed using chi-square tests and comparisons of continuous variables were performed using Wilcoxon's rank–sum test. The numbers of participants experiencing serious and nonserious adverse events, as reported during assessment visits, were compared between groups using chi-square tests. Mean differences in SPPB scores and 400-meter walk speed between intervention groups were estimated using repeated measures analysis of covariance, with the baseline value, gender (stratifying variable for randomization), intervention assignment, follow-up visit, and an intervention by visit interaction included in the model. Hypothesis tests for intervention effects at the 6-month and 12-month follow-up visits were performed using contrasts of the 6-month and 12-month intervention means. Overall comparison between groups for the SPPB score and 400-meter walk time were obtained using a contrast to compare average effects across both follow-up visits. The distribution of times until failure to complete the 400-meter walk (or death) was described using Kaplan–Meier plots. Hazard ratios and 95% confidence intervals were estimated using proportional hazards regression.
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7. The two randomized groups had similar baseline characteristics, except for a higher prevalence of diabetes in the PA group (Table 1).
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1 point and a higher number of participants in the SA group declined by 1 point (Figure 3). The 400-meter walk speed declined in the SA group and remained approximately stable in the PA group (p <.001) (Figure 2). The beneficial effects of PA on the SPPB score and on the 400-meter walk speed were fairly uniform across subgroups defined by age, gender, race, baseline physical performance, and comorbidity (Figure 4).
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There may be potential concern regarding the adherence to and long-term safety of regular structured PA interventions in older persons with functional limitations. In our study, the PA adherence rates were excellent, and comparable to or better than those achieved in other similar PA trials in older persons (19,20,37). The overall rates of nonserious adverse events were similar in the two groups. Among the specific nonserious adverse events, the PA group reported a higher rate of outpatient surgical procedures, which were primarily elective cataract surgery, and more often sought advice from a physician or medical professional for an abnormal heart rhythm. The former is unlikely to be related to the intervention, and the latter might be expected given the increase in heart rate the participants experienced during the PA sessions. Serious adverse events were equally balanced between the two groups.
Longitudinal observational studies suggest that regular PA not only may extend life expectancy, but also may reduce the risk of physical disability in later life (38–45). The benefit of PA on mobility disability may be mediated by ameliorating frequently disabling diseases, such as cardiovascular disease and depression (46), or by a direct effect on impairments such as reduced muscle strength (13,47,48), low cardiorespiratory fitness (49,50), and impaired balance (51–53).
Physical activity interventions, including resistance and endurance exercises, improve a variety of physical performance measures, such as walking speed, stair-climb speed, balance, and chair stands (13–20,54). Other short-term studies with limited sample size suggest that PA may improve the SPPB score (25,26). Our study provides new and definitive evidence that the SPPB score is significantly improved by a PA intervention, and this was consistently seen within age, gender, race, baseline physical performance, and comorbidity subgroups. The adjusted difference in average SPPB score between the two randomized groups (0.7 at 6 months and 0.6 at 12 months) ranks between a small and a substantial meaningful change (SPPB score changes of 0.5 and 1.0 point), according to the recent estimates published by Perera and colleagues (34). During follow-up in the PA group compared to the SA group, there was a significant shift in the distribution of participants that improved or declined by a substantial meaningful change (1 SPPB point), with a larger number of participants improving and lower number declining in the PA group (Figure 3). Accordingly, the number needed to treat (NNT) for improvement was approximately 6 at 6 months and 9 at 12 months. NNT for preventing decline was approximately 10 at both 6 and 12 months.
Major strengths of this study include the use of a simple, practical and broadly applicable PA intervention, the large sample size, the duration of follow-up, the excellent retention rate, and the single-blind design. The study was not powered to detect significant effects on major mobility disability, and it remains to be proven whether improvements in performance also translate into benefits on such clinically relevant health outcomes. In this regard, our study provides promising preliminary evidence that PA may prevent major mobility disability. However, a larger and longer-term randomized controlled trial is needed on this important topic [Espeland MA, Gill TM, Guralnik JM, et al. Designing Clinical Trials of Intervention for Mobility Disability: Results from the Lifestyle Interventions and Independence for Elders (LIFE) Pilot Trial. Unpublished observations] (55). Such a study will have crucial implications for prevention and public health in a rapidly aging society, and will fill an important gap in knowledge for practicing evidence-based geriatric medicine.
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APPENDIX |
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Contribution Key.--
Cooper Institute, Dallas, TX (Field Center).--
National Institute on Aging.--
Stanford University, Palo Alto, CA (Field Center).--
Tufts University.--
University of California, Los Angeles, Los Angeles, CA.--
VA San Diego Health Care System University of California, San Diego, San Diego, CA.--
University of Florida, Gainesville, FL (Administrative Coordinating Center).--
University of Pittsburgh, Pittsburgh, PA (Field Center).--
Wake Forest University, Winston-Salem, NC Field Center.--
Data Management, Analysis and Quality Control Center (DMAQC).--
Yale University.--
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The Wake Forest University Field Center was, in part, supported by the Claude D. Pepper Older American Independence Center #1 P30 AG21332.
The Pittsburgh Field Center was partially supported by the Pittsburgh Claude D. Pepper Center P30 AG024827.
Dr. Fielding's contribution is partially supported by the U.S. Department of Agriculture, under agreement No. 58-1950-4-401. Any opinions, findings, conclusion, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
Dr. Pahor's contribution is partially supported by the Geriatric Research, Education and Clinical Center (GRECC), Malcom Randall Veteran's Affairs Medical Center, North Florida/South Georgia Veterans Health System, Gainesville, Florida.
Dr. Gill is the recipient of a Midcareer Investigator Award in Patient-Oriented Research (K24AG021507) from the National Institute on Aging.
This study was funded by a grant from the National Institute on Aging (NIA). The NIA scientists had substantial involvement in the study design, data collection, analysis, interpretation and manuscript preparation.
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Received July 24, 2006
Accepted July 25, 2006
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