a categorización de documentos es el proceso por el cual se asocian una o más categorías a textos escritos en un lenguaje natural basándose tan sólo en su L contenido. Aunque es posible construir de manera "manual" un categorizador, las técnicas estadísticas y, por tanto, automáticas son actualmente las preferidas puesto que no sólo ofrecen un rendimiento muy adecuado sino que resulta mucho más sencillo
Tai chi and postural stability in patients with parkinson's diseaseTai Chi and Postural Stability in Patients with Parkinson's Disease Fuzhong Li, Ph.D., Peter Harmer, Ph.D., M.P.H., Kathleen Fitzgerald, M.D., Elizabeth Eckstrom, M.D., M.P.H., Ronald Stock, M.D., Johnny Galver, P.T., Gianni Maddalozzo, Ph.D., and Sara S. Batya, M.D.
Patients with Parkinson's disease have substantially impaired balance, leading to di- From the Oregon Research Institute (F.L.),
the Oregon Medical Group (K.F.), and the minished functional ability and an increased risk of falling. Although exercise is rou- PeaceHealth Medical Group–Oregon tinely encouraged by health care providers, few programs have been proven effective. (R.S.) — all in Eugene; Willamette Univer- sity (P.H.) and BPM Physical Therapy Cen-ter (J.G.) — both in Salem, OR; Oregon Health and Science University, Portland We conducted a randomized, controlled trial to determine whether a tailored tai chi (E.E.); Oregon State University, Corvallis program could improve postural control in patients with idiopathic Parkinson's (G.M.); and Oregon Neurology Associ- ates, Springfield (S.S.B.). Address reprint disease. We randomly assigned 195 patients with stage 1 to 4 disease on the Hoehn and requests to Dr. Li at the Oregon Research Yahr staging scale (which ranges from 1 to 5, with higher stages indicating more Institute, 1715 Franklin Blvd., Eugene, OR severe disease) to one of three groups: tai chi, resistance training, or stretching. The 97403, or at [email protected].
patients participated in 60-minute exercise sessions twice weekly for 24 weeks. The N Engl J Med 2012;366:511-9.
primary outcomes were changes from baseline in the limits-of-stability test (maxi- Copyright 2012 Massachusetts Medical Society. mum excursion and directional control; range, 0 to 100%). Secondary outcomes included measures of gait and strength, scores on functional-reach and timed up-and- go tests, motor scores on the Unified Parkinson's Disease Rating Scale, and number RESULTS
The tai chi group performed consistently better than the resistance-training and
stretching groups in maximum excursion (between-group difference in the change from baseline, 5.55 percentage points; 95% confidence interval [CI], 1.12 to 9.97; and 11.98 percentage points; 95% CI, 7.21 to 16.74, respectively) and in directional con- trol (10.45 percentage points; 95% CI, 3.89 to 17.00; and 11.38 percentage points; 95% CI, 5.50 to 17.27, respectively). The tai chi group also performed better than the stretching group in all secondary outcomes and outperformed the resistance- training group in stride length and functional reach. Tai chi lowered the incidence of falls as compared with stretching but not as compared with resistance training. The effects of tai chi training were maintained at 3 months after the intervention. No serious adverse events were observed.
Tai chi training appears to reduce balance impairments in patients with mild-to-
moderate Parkinson's disease, with additional benefits of improved functional capac- ity and reduced falls. (Funded by the National Institute of Neurological Disorders and Stroke; ClinicalTrials.gov number, NCT00611481.) n engl j med 366;6 nejm.org february 9, 2012 The New England Journal of Medicine Downloaded from nejm.org at CLINICIANS HEALTH CHANNEL on February 15, 2012. For personal use only. No other uses without permission. Copyright 2012 Massachusetts Medical Society. All rights reserved. Movement impairments, especially full text of this article at NEJM.org. The trial pro- loss of the ability to maintain standing tocol, also available at NEJM.org, was approved by balance, adversely affect function and the institutional review board of the Oregon Re- quality of life in patients with Parkinson's dis- search Institute, and written informed consent was ease.1,2 With progression of the disease, patients obtained from all participants. All authors vouch lose postural stability and have gait dysfunction, for the completeness and accuracy of the data and difficulty managing activities of daily living, and attest to the fidelity of the trial to the protocol.
frequent falls.3,4 Although some motor dysfunc- tion, such as tremor, may be alleviated with drug STUDY PARTICIPANTS
therapy, characteristics such as postural instability Study participants were recruited from four Oregon are less responsive to medication and require alter- cities (Eugene, Corvallis, Salem, and Portland) by native approaches.5,6 means of newspaper advertisements, referrals from Exercise is an integral part of the management neurologists or physical therapists, and informa- of Parkinson's disease because physical activity has tion distributed to local support groups for persons been shown to retard the deterioration of motor with Parkinson's disease. Eligibility criteria includ- functions and to prolong functional indepen- ed a clinical diagnosis of Parkinson's disease, with dence.7-9 Resistance-based exercises that address a disease severity rating of stage 1 to 4 on the deficits in balance and strength have shown posi- Hoehn and Yahr scale (which ranges from 1 to 5, tive effects.10-12 However, they require safety mon- with higher scores indicating more severe disease)4; itoring and are equipment-dependent. Research on an age of 40 to 85 years; at least one score of 2 or alternative forms of exercise that could improve more for at least one limb for the tremor, rigidity, balance, gait, and function in patients with Parkin- postural stability, or bradykinesia items in the son's disease is scarce.
motor section of the Unified Parkinson's Disease Tai chi, a balance-based exercise, has been Rating Scale (UPDRS) III)18; stable medication use; shown to improve strength, balance, and physical ability to stand unaided and walk with or without function and to prevent falls in older adults.13-15 an assistive device; medical clearance for participa- Two pilot studies suggest that it may also improve tion; and willingness to be assigned to any of the axial symptoms of Parkinson's disease, such as three interventions. Exclusion criteria were current postural stability.16,17 However, there exist few data participation in any other behavioral or pharma- from large-scale randomized trials that have ad- cologic study or instructor-led exercise program, a dressed the efficacy of tai chi in this context.
Mini–Mental State examination19 score lower than The primary aim of this study was to examine 24 (indicating some degree of cognitive impair- whether a tailored tai chi program could improve ment), debilitating conditions or vision impairment postural stability in patients with Parkinson's that would impede full participation in the study, disease. Because the program emphasized rhyth- and unavailability during the study period.
mic weight shifting, symmetric foot stepping, and controlled movements near the limits of stability, SCREENING AND RANDOMIZATION
we hypothesized that tai chi would be more effec- Research staff screened patients by telephone. tive in improving postural stability in limits-of- Those who met prescreening criteria underwent an stability tasks than a resistance-based exercise in-person evaluation and baseline assessment. Eli- regimen or low-impact stretching (control).
gible participants were randomly assigned to one of the interventions, in a ratio of 1:1:1, without strat- ification, with the use of permuted-block random- ization once eligibility was confirmed and baseline STUDY DESIGN
assessments were completed. Outcome assessors We designed a randomized clinical trial to compare were unaware of group assignments.
the effects of exercise at 6 months in a group of patients assigned to tai chi classes with the effects EXERCISE INTERVENTIONS
in groups assigned to resistance-training or stretch- Tai Chi ing classes. Each group participated in a 60-minute The protocol consisted of six tai chi movements17 class that met twice weekly for 24 weeks. An ex- integrated into an eight-form routine (see the Sup- panded description of the methods is provided in plementary Appendix for more details).20,21 Be- the Supplementary Appendix, available with the cause the goal was to maintain balance through n engl j med 366;6 nejm.org february 9, 2012 The New England Journal of Medicine Downloaded from nejm.org at CLINICIANS HEALTH CHANNEL on February 15, 2012. For personal use only. No other uses without permission. Copyright 2012 Massachusetts Medical Society. All rights reserved. Tai Chi and Parkinson's Disease postural control, the protocol was specifically NeuroCom). Maximum excursion is an assessment designed to tax balance and gait by having par- of the limits of self-initiated movements as patients ticipants perform symmetric and diagonal move- shift or lean their center of gravity, without falling, ments, such as weight shifting, controlled displace- toward the theoretical limit (100%) in each of eight ment of the center of mass over the base of support, target directions. Directional control, a measure of ankle sways, and anterior–posterior and lateral movement accuracy, is calculated by comparing the stepping. The first 10 weeks emphasized the mas- amount of movement toward the target with the tery of single forms through multiple repetitions; amount of extraneous movement. Scores on both later weeks focused on repetitions to enhance bal- measures range from 0 to 100%, with higher per- ance and increase locomotion. Natural breathing centages indicating better balance or control.
was integrated into the training routine.
Gait (stride length and walking velocity) was quan- The protocol, developed from the exercise litera- tified with the use of a computerized 4.3-m (14 ft) ture,11,22-25 focused on strengthening the muscles walkway (GAITRite, CIR Systems). Participants that are important for posture, balance, and gait. were instructed to walk at their normal pace for Resistance (with weighted vests and ankle weights) four trials; the results were averaged to derive a was introduced at week 10. Weighted-vest resis- score for each measure, with higher scores indicat- tance was initially set at 1% of body weight and was ing better gait ability. Strength of bilateral knee increased by approximately 1 to 2% of body weight, extensors and flexors was measured at an angular depending on each participant's tolerance, every velocity of 60 degrees per second with the use of an fifth week until 5% of body weight was achieved. isokinetic dynamometer (Biodex System 3, Biodex Ankle weights started at 0.45 kg (1 lb) per limb and Medical Systems). Summary peak torque values (in were gradually increased to 1.36 kg (3 lb). The rou- Newton meters [Nm]) of five cycles of maximal tine involved 8 to 10 exercises, including forward extension and flexion were calculated from the av- and side steps, squats, forward and side lunges, erage of measurements of both limbs. The func- and heel and toe raises, performed in 1 to 3 sets of tional-reach test26 assessed the maximal distance a 10 to 15 repetitions. Progression was modified participant could reach forward beyond arm's for participants with physical limitations. Natural length while maintaining a fixed base of support breathing was emphasized during the training in a standing position, with higher scores indicat- ing better balance. The timed up-and-go test27 measured the time (in seconds) taken to rise from a chair, walk 3.1 m (10 ft), return, and sit down, This control condition was designed to provide a with a shorter time indicating better mobility. Par- low-intensity exercise program with the social in- ticipants' motor symptoms were assessed with teraction and enjoyment inherent in the two other the 14-item UPDRS III18; scores range from 0 to interventions but without similar training benefits 56, with lower values indicating less motor disabil- in lower-extremity weight bearing, strength, or bal- ity. Assessors were trained by a board-certified ance.13,20 The core activities encompassed a vari- neurologist according to the standard protocol.28 ety of seated and standing stretches involving the Interrater reliability was 0.96. Falls were monitored upper body (neck, upper back, shoulders, chest, and by means of daily "fall calendars" that were main- arms) and lower extremities (quadriceps, ham- tained by the study participants13 and collected strings, calves, and hips), with the use of gentle monthly throughout the intervention or until a par- joint extension and flexion and trunk rotation. ticipant withdrew from the study.
Abdominal breathing, with an emphasis on in- haling and exhaling to maximum capacity, and TEST PROCEDURES
relaxation of major muscles were also included.
Outcome measures were assessed at baseline, at 3 and 6 months, and 3 months after completion of the intervention. Participants were instructed Primary outcomes consisted of two indicators of to follow their normal schedules for physical ac- postural stability — maximum excursion and di- tivity and medication during the 6-month inter- rectional control — as measured by computerized vention period. Assessments were conducted dur- dynamic posturography (Balance Master System, ing times when participants were in "on" periods n engl j med 366;6 nejm.org february 9, 2012 The New England Journal of Medicine Downloaded from nejm.org at CLINICIANS HEALTH CHANNEL on February 15, 2012. For personal use only. No other uses without permission. Copyright 2012 Massachusetts Medical Society. All rights reserved. (i.e., when medication was working and symp- toms were controlled). The participants' antipar- kinsonian medications were monitored by means BASELINE CHARACTERISTICS OF THE PARTICIPANTS
of a self-reported measure.29 From May 2008 through November 2010, a total of 309 persons were screened for eligibility; 195 quali- fied and underwent randomization (Fig. 1 in the All primary and secondary analyses were conduct- Supplementary Appendix). Table 1 shows the base- ed on an intention-to-treat basis. Between-group line characteristics of the study population. A total differences in demographic and baseline variables of 164 persons (84%) were at stage 2 or higher on were tested with a chi-square test for categorical the Hoehn and Yahr staging system (range, 1 to 4; variables and a one-way analysis of variance for median, 2.5). The groups were well matched with regard to baseline characteristics, including age, Intervention effects on primary and secondary sex, duration of Parkinson's disease, Hoehn and continuous outcome measures were compared by Yahr stages, and baseline study outcomes of in- means of mixed repeated-measures analysis of terest.
variance, with and without adjustment for baseline A total of 176 participants completed their and time-varying covariates (e.g., age, sex, disease assigned interventions, and 185 provided complete stage, health status, medication use and change, data on the outcome measures at follow-up. There and level of physical activity). Pairwise compari- were no significant differences in the baseline de- sons between the tai chi group and the two other mographic variables or primary outcomes between groups were conducted only if the omnibus F-test participants who completed the trial and those statistics indicated that the null hypothesis should who did not. The average attendance across the be rejected. Independent-sample t-tests (with 95% 24-week period was 37 sessions (77%; 37 of 48 in confidence intervals) were used to compare group tai chi; 37 of 48 in resistance training; and 38 of means. Paired t-tests were used to examine within- 48 in stretching; median, 39; range, 3 to 48). A group changes from baseline to 6 months. Nega- total of 137 participants (70%) attended 36 or more tive binomial regression was used to model data sessions (≥75%). Attendance did not differ signifi- on falls and to derive incidence-rate ratios (with cantly among the groups (P = 0.67). There were no 95% confidence intervals). The same analytic pro- significant within-group changes in participants' cedures were used to examine the sustainability of outside physical activity (P = 0.23) or use of anti- the intervention effects.
parkinsonian medication (P = 0.16).
We calculated that a sample of 45 participants per group would provide at least 80% power to PRIMARY OUTCOMES
detect a between-group difference of 6 percentage Mean (±SD) between-group differences in out- points in maximum excursion and 10 percentage comes at 6 months are shown in Table 2. The par- points in directional control from baseline to ticipants in the tai chi group performed significant- 6 months, assuming a 15% attrition rate, at a two- ly better than those in the resistance-training and tailed alpha level of 0.05. These predicted percent- stretching groups on the primary outcomes. The tai age-point differences equate to a medium effect chi group had better performance than the resis- size of 0.30 or greater (the difference between two tance-training group in maximum excursion, with means divided by the pooled standard deviation for a between-group difference of 5.55 percentage the data). For the primary outcomes, a two-tailed points (95% confidence interval [CI], 1.12 to 9.97; alpha level of 0.01 (for four corrected comparisons P = 0.01), and in directional control, with a between- by the Bonferroni method) was considered to indi- group difference of 10.45 percentage points (95% cate statistical significance. Statistical analyses CI, 3.89 to 17.00; P = 0.002). The tai chi group also were performed with the use of SPSS software, had significantly better performance than the version 17 (IBM), and Stata software, version 11 stretching group in both maximum excursion and directional control, with between-group differenc- n engl j med 366;6 nejm.org february 9, 2012 The New England Journal of Medicine Downloaded from nejm.org at CLINICIANS HEALTH CHANNEL on February 15, 2012. For personal use only. No other uses without permission. Copyright 2012 Massachusetts Medical Society. All rights reserved. Tai Chi and Parkinson's Disease Table 1. Demographic and Clinical Characteristics of the Study Participants at Baseline.*
Female sex — no. (%) Body-mass index† Hoehn and Yahr stage — no. (%) Age at initial diagnosis — yr Duration of disease — yr Antiparkinsonian medications taken — no.
Levodopa or carbidopa Pramipexole or ropinirole Self-reported health status — no. (%) Very good or excellent Score for self-reported habitual physical activity‡ Self-reported coexisting chronic conditions — no. (%)§ * Plus–minus values are means ±SD. The chi-square test was used for categorical variables, and one-way analysis of variance for continuous variables. There were no significant between-group differences in any baseline characteristics. A more detailed listing of baseline characteristics is available in the Supplementary Appendix.
† The body-mass index is the weight in kilograms divided by the square of the height in meters.
‡ Activity was measured by means of the Physical Activity Scale for the Elderly,30 with scores ranging from 7 to 313 (derived by multiplying activity participation by established item weights). Higher scores indicate higher levels of habit- ual physical activity.
§ Conditions included arthritis, heart disease, high blood pressure, lung disease, diabetes, osteoporosis, depression, chronic back pain, and cancer; the number of conditions per participant ranged from 0 to 9.
es of 11.98 percentage points (95% CI, 7.21 to 16.74) training group had a mean increase of 4.02 per- and 11.38 percentage points (95% CI, 5.50 to 17.27), centage points in maximum excursion (P = 0.02) respectively (P<0.001 for both comparisons). The but did not have a significant change in direc- significant effect of tai chi remained after adjust- tional control (−2.43 percentage points, P = 0.35). ment for covariates.
No significant change from baseline was observed From baseline to 24 weeks, the participants in in the stretching group.
the tai chi group had a mean increase of 9.56 per- centage points in maximum excursion and 8.02 SECONDARY OUTCOMES
percentage points in directional control (P<0.001 Significant between-group differences were ob- for both outcomes). Participants in the resistance- served after 24 weeks (Table 2). The tai chi group n engl j med 366;6 nejm.org february 9, 2012 The New England Journal of Medicine Downloaded from nejm.org at CLINICIANS HEALTH CHANNEL on February 15, 2012. For personal use only. No other uses without permission. Copyright 2012 Massachusetts Medical Society. All rights reserved. had significantly better performance on the mea- velocity (P = 0.001), 14.6 Nm in knee extension sures of gait and strength, better scores on the (P<0.001), 8.9 Nm in knee flexion (P = 0.001), and functional-reach and timed up-and-go tests, and 2.2 cm in functional reach (P = 0.007), as well as better UPDRS III scores, as compared with the decreases of 1.00 second on the up-and-go test and stretching group (P<0.001 for all comparisons). The 5.07 points in the UPDRS III score (P<0.001 for tai chi group also outperformed the resistance- both comparisons). No significant change from training group on stride length and functional baseline was observed in the stretching group, ex- reach (P = 0.01 for both comparisons).
cept for deterioration in walking velocity (a de- From baseline to 24 weeks, participants in the crease of 4.50 cm per second, P = 0.01) and im- tai chi group had mean increases of 10.3 cm in provement in the UPDRS III scores (a decrease of stride length (P<0.001), 10.4 cm per second in 1.40 points, P = 0.05).
walking velocity (P<0.001), 13.9 Nm in knee exten- A total of 381 falls in 76 of the 195 participants sion (P = 0.001), 5.1 Nm in knee flexion (P = 0.01), (39%) were documented during the 6-month study and 5.0 cm in functional reach, (P<0.001), with period (Table 3). The incidence rate of falls was decreases of 1.05 seconds on the up-and-go test lower in the tai chi group (0.22 per participant- and 6.42 points in the UPDRS III score (with month) than in the other two groups. Participants lower scores indicating improvement). Similar in the tai chi group had 67% fewer falls than those improvements were observed in the resistance- in the stretching group (incidence-rate ratio, 0.33; training group: mean increases of 4.3 cm in stride 95% CI, 0.16 to 0.71). They had marginally fewer length (P = 0.01), 10.0 cm per second in walking falls than the participants in the resistance-train- Table 2. Study Measures at Baseline and 6 Months and Between-Group Differences in the Change from Baseline.*
Between-Group Difference in Mean Change from Baseline†
Tai Chi vs. Resistance Tai Chi vs. Stretching Maximum excursion (%)‡ 5.55 (1.12 to 9.97) 11.98 (7.21 to 16.74) Directional control (%)§ 62.56±21.62 10.45 (3.89 to 17.00) 11.38 (5.50 to 17.27) Stride length (cm)¶ 5.9 (1.5 to 10.4) 12.3 (8.3 to 16.4) Gait velocity (cm/sec)‖ 0.5 (−6.2 to 7.1) 14.9 (9.8 to 20.1) Peak torque knee extension −0.6 (−10.8 to 9.5) 13.5 (3.4 to 23.6) Peak torque knee flexion −3.8 (−10.2 to 2.7) 7.7 (1.9 to 13.6) Functional reach (cm)†† n engl j med 366;6 nejm.org february 9, 2012 The New England Journal of Medicine Downloaded from nejm.org at CLINICIANS HEALTH CHANNEL on February 15, 2012. For personal use only. No other uses without permission. Copyright 2012 Massachusetts Medical Society. All rights reserved. Tai Chi and Parkinson's Disease Table 2. (Continued.)
Between-Group Difference in Mean Change from Baseline†
Tai Chi vs. Resistance Tai Chi vs. Stretching Timed up and go (sec)‡‡ −0.05 (−0.55 to 0.46) −1.03 (−1.58 to −0.47) <0.001 UPDRS III score§§ −1.34 (−3.28 to 0.59) −5.02 (−6.90 to −3.13) <0.001 * Plus–minus values are means ±SD. NS denotes not significant. A more detailed version of the table, including results from the 3-month postintervention follow-up, is available in the Supplementary Appendix.
† Mixed repeated-measures analysis of variance (group by time) with baseline, 3-month, and 6-month values indicated a significant between- group difference across all outcome measures (range, P = 0.006 to P<0.001). Analyses were performed on an intention-to-treat basis. Point estimates and estimates falling within the 95% confidence interval were generated from independent t-tests for group differences. (See also Fig. 1 in the Supplementary Appendix.) ‡ Maximum excursion was assessed as the farthest distance displaced by the participant's center of gravity during performance of leaning and reaching tasks. Scores range from 0 to 100%, with higher percentages indicating better balance.
§ Directional control was assessed as the amount of movement toward a target, as compared with extraneous movement (away from the target), defined as the ratio of the amount of intended movement minus the amount of extraneous movement, divided by the amount of intended movement. The composite score of eight directions was used for analyses. Scores range from 0 to 100%, with higher percentages indicating better movement control.
¶ Stride length was measured as the distance between the heel points of two consecutive footprints of the same foot. Higher scores indicate greater stride length.
‖ Gait velocity was measured by dividing the distance traveled by the ambulation time. Higher scores indicate greater gait velocity.
** Peak torque was measured at an angular velocity of 60 degrees per second. Values are given in Newton meters (Nm). Results were the av- erage of five repetitions of measurements at both limbs, with higher values indicating greater strength.
†† Functional reach was assessed as the maximal distance a participant could reach forward beyond arm's length while maintaining a fixed base of support in a standing position. Higher scores indicate better balance.
‡‡ Timed up and go was measured as the time taken to rise from a chair, walk 3.1 m (10 ft), return, and sit down. Higher scores indicate better §§ The 14-item motor section of the Unified Parkinson's Disease Rating Scale (UPDRS) III was scored on a 5-point Likert scale from 0 to 4, with 0 representing no impairment and 4 representing marked impairment. Lower values indicate less motor disability. A change of 5 points or more in the score is considered clinically meaningful.31 ing group (incidence-rate ratio, 0.47; 95% CI, 0.21 to 1.00). All intervention effects remained significant after adjustment for baseline and time- We found that a program of twice-weekly tai chi for varying covariates.
24 weeks, as compared with a resistance-training program or a stretching program, was effective in MAINTENANCE OF INTERVENTION GAINS
improving postural stability and other functional Analyses at the 3-month postintervention follow- outcomes in patients with mild-to-moderate Par- up indicated that gains in primary and secondary kinson's disease. Tai chi training also significantly outcomes in the tai chi group were maintained reduced the incidence of falls, as compared with the (Table 2 in the Supplementary Appendix) and that, stretching program. Improvements in primary and in this postintervention period, participants in the secondary outcomes were maintained 3 months tai chi group had fewer falls than those in the after the intervention, a finding that is consistent stretching group (incidence-rate ratio, 0.31; 95% CI, with prior research involving adults 70 years of age 0.14 to 0.67; P = 0.003) and those in the resistance- or older.13 No serious adverse events were observed training group (incidence-rate ratio, 0.40; 95% CI, during tai chi training, indicating the safety and 0.18 to 0.88; P = 0.02) usefulness of this intervention for persons with The improvement in maximum excursion with No major adverse events were noted (Table 4).
reduced deviation in movement, as shown on the n engl j med 366;6 nejm.org february 9, 2012 The New England Journal of Medicine Downloaded from nejm.org at CLINICIANS HEALTH CHANNEL on February 15, 2012. For personal use only. No other uses without permission. Copyright 2012 Massachusetts Medical Society. All rights reserved. reaching forward to take objects from a cabinet, Table 3. Self-Reported Falls during the 6-Month Intervention, According to
transitioning from a seated to a standing position (and from standing to seated), and walking, while reducing the probability of falls. Similarly, the marked increase in gait velocity in participants in the tai chi group was associated with significant No. of falls — no. of participants (%) increases in stride length. These improvements in gait characteristics support the efficacy of tai chi in alleviating the bradykinetic movements associated with Parkinson's disease.
The tai chi protocol stresses weight shifting and ankle sway to effectively move the person's center Rate — no./participant-month of gravity toward the limits of stability, alternating between a narrow stance and a wide stance to * Falls were defined as unintentionally coming to rest on the floor or the ground or falling and hitting objects such as stairs or pieces of furniture.
continually change the base of support, increasing † A significant difference was found in the incidence-rate ratio between the tai support-leg standing time and trailing-leg swing chi and stretching groups (P = 0.005); a nonsignificant difference was found time, engaging rotational trunk movements with between the tai chi and resistance-training groups (P = 0.05).
upright posture, and performing heel-to-toe (forward) and toe-to-heel (backward) stepping Table 4. Adverse Events.
movements to strengthen dorsiflexion and plantar flexion. These inherent training features may have led to improved postural control and walking abil- number of events ity. Although these improvements indicate that tai chi would be effective in enhancing neuromuscular rehabilitation, the mechanisms behind the thera- peutic change in participants' motor control and Muscle soreness or pain mobility remain less understood and warrant fu- Dizziness or faintness ture exploration.
Symptoms of hypotension Falls are a common and sometimes life-threat- ening event in patients with Parkinson's dis- ease.32,33 However, to our knowledge, no clinical Symptoms of chest pain trial has shown the efficacy of exercise in reducing falls in this population. Thus, this study adds to Symptoms of hypotension the behavior-based treatment literature by showing that tai chi can effectively reduce the incidence of falls in patients with Parkinson's disease.
This study has some limitations. First, given the * Values are the number of events that occurred during in-class sessions.
behavior-based treatments, participants were aware † Data on falls are based on the total falls reported by participants in their "falls of their intervention assignments. This awareness may have introduced biases in the results, since ‡ Values are the number of events that occurred outside class settings (i.e., in the home or during an assessment). Participants did not engage in home persons interested in participating may have had practice; events presented are those that occurred in a home environment positive expectations about the benefits of exercise. while participants engaged in a habitual activity (self-reported) or that were Second, we did not include a nonexercise control observed during a laboratory assessment (assessor-reported).
group, so the net gain of tai chi training cannot be gauged. However, the results of this trial show that posturographic limits-of-stability tests, suggests tai chi is more effective than low-intensity, low- that tai chi training reduced dyskinesia by increas- impact exercise programs in alleviating the symp- ing the ability of the participants to adopt effective toms of Parkinson's disease and improving func- sway strategies (at the ankle or hip), engage in tional ability. Finally, all participants were tested controlled movements with improved balance con- during "on" periods, which may have masked un- trol near the limit of stability, or both. Clinically, derlying changes induced by the training inter- these changes indicate increased potential for ef- ventions.
fectively performing daily life functions, such as In conclusion, tai chi appears to be effective as n engl j med 366;6 nejm.org february 9, 2012 The New England Journal of Medicine Downloaded from nejm.org at CLINICIANS HEALTH CHANNEL on February 15, 2012. For personal use only. No other uses without permission. Copyright 2012 Massachusetts Medical Society. All rights reserved. Tai Chi and Parkinson's Disease a stand-alone behavioral intervention designed to kinson's disease stage diagnoses for their participating patients; improve postural stability and functional ability the project instructors (Vicki Anderson, Denise Thomas-Morrow, Don Hildenbrand, Brian McCall, James Lusk, Nancy Nelson, Teena in people with Parkinson's disease.
Hall, Machiko Shirai, and Julie Tye); the research assistants (Debbie Supported by a grant (NS047130) from the National Institute Blanchard, Kristen Briggs, Ruben Guzman, Daehan Kim, Lisa of Neurological Disorders and Stroke.
Marion, Arissa Fitch-Martin, Kimber Mattox, Julia Mazur, Donna No potential conflict of interest relevant to this article was McElroy, Jordyn Smith, and Rachel Tsolinas); the physical thera- pists (Andrea Serdar, Jeff Schlimgen, Jennifer Wilhelm, Ryan Rock- Disclosure forms provided by the authors are available with wood, and Connie Amos at Oregon Health and Science University); the full text of this article at NEJM.org.
the study data analyst, Shanshan Wang; Kathryn Madden and the We thank all the study participants (in Eugene, Corvallis, Salem, members of the institutional review board at the Oregon Research and Portland) for their support and dedication to this research Institute for their careful scrutiny of the study protocol; and Ron project; the neurologists for providing medical clearance and Par- Renchler for proofreading earlier drafts of the manuscript.
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