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From the Department of Health and Exercise Science (Drs. Foy, Rejeski, Berry, and Mr. Woodward), Wake Forest University, Winston-Salem, NC; and the Department of Biostatistics (Mr. Zaccaro), Wake Forest University Baptist Medical Center, Winston-Salem, NC.
Drs. Foy and Rejeski contributed equally to the
preparation of this article.
Correspondence to: W. Jack Rejeski, PhD, Department of Health and Exercise Science, PO Box 7868, Winston-Salem, NC 27109
Abstract
Study objectives: To determine whether long-term treatment with exercise therapy results in more favorable, disease-specific, health-related quality of life (HRQL) compared with short-term treatment with exercise therapy; and to determine whether there are gender differences in disease-specific HRQL among individuals randomized into the two treatment groups.
Design: Randomized clinical trial.
Setting: Center-based exercise therapy unit at a university.
Participants: One hundred forty patients with COPD; 118 completed trial.
Interventions: Short-term exercise therapy (3 months); long-term exercise therapy (18 months).
Measurements: Chronic Disease Respiratory Questionnaire (CRQ).
Results: After 3 months of treatment, there were significant improvements in all CRQ scores for men and women (p < 0.01), and for the total sample (p < 0.01). At 18 months, individuals randomized into the long-term group had significantly more favorable scores than the short-term group for dyspnea (p = 0.03), fatigue (p < 0.01), emotional function (p = 0.04), and mastery (p = 0.04). However, these effects were moderated by gender. That is, men in the long-term group reported significantly more favorable scores than men in the short-term group for dyspnea (0.04), fatigue (p < 0.001), emotional function (p = 0.02), and mastery (p = 0.02). At the 18-month assessment, there were no differences between long-term and short-term exercise therapy for women on any of the subscales of the CRQ.
Conclusions: Taken collectively, the CRQ data demonstrate that long-term exercise therapy has little added benefit for women over short-term exercise therapy; however, men derive significant benefits from extended training.
Key Words: pulmonary rehabilitation • quality of life • exercise training • gender differences • COPD
COPD is characterized by a progressive and insidious chronic airway obstruction that produces shortness of breath. This relentless disease is the fourth-leading cause of death in the United States and is a major contributing factor to the high prevalence of morbidity and disability found among older adults.1 Because there is no cure for this disease, an important focus of clinical medicine has been the prevention of further decline in physical function and the enhancement of health-related quality of life (HRQL). In this regard, two meta-analytic reviews have concluded that pulmonary rehabilitation (PR), which relies heavily on exercise therapy, has favorable effects on patients’ HRQL.2 3 However, much of existing research on PR has focused on short-term exercise training and does not permit investigators to disentangle the effects of exercise from other interventions that often occur as a part of comprehensive PR. In addition, since most research has been conducted on men, little is known about the effects of exercise therapy on women. The current investigation was designed to address these shortcomings.
Cambach et al,3 in their meta-analysis of 18 PR studies conducted from 1977 to 1997, reported on 11 randomized controlled trials (RCTs) that involved both exercise therapy and some quality-of-life measures.3 In nearly half of these 11 RCTs (5 of the 11 studies conducted since 1987), the outcome measure of choice had been one or more domains of the Chronic Respiratory Disease Questionnaire (CRQ), developed by Guyatt and his colleagues in 1987.4 Taken collectively, the meta-analysis by Cambach et al3 concluded that PR resulted in significant summary effect sizes for all domains of the CRQ. Moreover, the authors demonstrated that improvements recorded on the CRQ were more favorable for patients who received exercise therapy as part of their PR.
Despite empirical evidence in support of the positive effects that physical rehabilitation has on the HRQL of patients with COPD,2 3 5 there are a number of limitations in this body of research. For example, in the review by Cambach et al, 3 11 of the 14 RCTs reviewed had interventions that lasted 3 months, and 7 of the 11 RCTs that included exercise therapy and a measure of HRQL were characterized by small sample sizes (ie, < 40 subjects). In addition, 8 of the RCTs involving exercise therapy and HRQL also involved other components of PR, such as breathing exercises, social support, and relaxation training. Finally, as mentioned earlier, very little attention has been given to the study of women. For example, only 1 of the 14 trials6 examined in the meta-analysis by Lacasse et al2 included an equal number of male and female participants. Furthermore, in this latter study, there were no analyses reported for gender differences among participants. Additionally, in 13 of the 14 trials reviewed by Lacasse et al,2 < 15% of the participants studied were women. Given the strong evidence in the cardiovascular disease literature that supports the scientific study of gender differences,7 8 it seems appropriate to consider gender as a potential moderator variable within the context of outcome research in PR.
With these issues in mind, the current study was designed to monitor changes in the CRQ that occur when patients with COPD exercise in structured group settings for either 3 months or 18 months. The study sample was large and included a good representation of both men and women. This latter feature of the sampling scheme enabled us to evaluate the potential moderating effect of gender on any observed effects that exercise has a disease-specific measure of HRQL.
Materials and Methods
Patients
Patients for this study were recruited from the Triad region of
North Carolina, within a 50-mile radius of Wake Forest University.
Recruitment strategies consisted of mass mailings, mass media
advertisements, and requests from local physicians targeting
age-eligible older adults with COPD. The final sample consisted of 78
men and 62 women > 50 years old. A diagram that describes the
recruitment yield and trial adherence can be found in Figure 1
. All participants met the following
inclusion criteria: (1) either disability associated with shortness of
breath or diagnosis of chronic bronchitis and/or emphysema; (2)
ambulatory; (3) between the ages of 55 years and 80 years old; (4) an
expiratory airflow limitation such that the
FEV1/FVC was < 70% and the
FEV1 was > 20% of predicted measure; and (5)
not actively engaging in regular exercise or PR for the preceding 6
months. Exclusion criteria included concurrent history of: (1) active
treatment for cancer; (2) severe congestive heart failure; (3) stroke;
(4) peripheral vascular disease; (5) coronary artery disease; (6)
valvular heart disease; (7) major psychiatric disease; (8) severe
anemia; (9) liver or renal disease; (10) uncontrolled diabetes or
hypertension; (11) orthopedic impairment; (12) blindness or deafness;
(13) inability to perform exercise due to physical disability or
positive exercise stress test; (14) cognitive impairment; and (15)
alcohol consumption of greater than two drinks per day for the
proceeding 2 months. Demographic and biometric characteristics of the
participants are discussed in the "Results" section (Table 1
).
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Attendance:
Attendance to the structured exercise therapy
sessions was recorded for each participant in the study. Percent of
compliance for attendance was defined as the number of sessions that
the participant attended, divided by the number of sessions offered at
the center, multiplied by 100. For example, if a participant attended
18 sessions of 36 offered, her percent compliance would be
(18/36)x100, or 50%. In addition, an average exercise intensity was
calculated for each participant and was expressed as a percentage of
peak heart rate.
Percentage of Peak Heart Rate:
Percentage of peak heart rate
achieved during a symptom-limited, graded exercise test was defined
according to the following formula: THRR =
[(SLMHRRHR)xdesired percentage] + RHR. In this formula,
THRR = training heart rate range, SLMHR = symptom-limited
maximum heart rate achieved during the graded exercise test, and
RHR = resting heart rate. The average compliance for exercise
intensity was determined by aggregating data across the total number of
sessions completed by each participant. During the exercise therapy,
heart rates were recorded by using a pulse oximeter (model AD-1000;
Armstrong Medical; Lincolnshire, IL). Accuracy for heart rate
measurement was ± 2%, and averaging was done over an 8-s interval.
Procedures
Prior to participation in the intervention, patients visited the
laboratory on three separate occasions for preliminary screening tests,
baseline assessments, and completion of an informed consent. Once
participants qualified for participation in the trial, they then
engaged in 3 months of exercise therapy. At the end of this period,
participants were tested for a second time and then randomized into
either the short-term treatment or long-term treatment groups. Those
patients randomized into short-term treatment no longer continued
involvement in structured exercise therapy, whereas those assigned to
long-term treatment continued exercise training for an additional 15
months. Participants assigned to short-term treatment were encouraged
to engage in independent, unmonitored, home-based exercise. An
additional assessment was taken 15 months after the randomization.
Therefore, we report data from the baseline, 3-month, and 18-month
assessments.
Exercise Therapy Intervention
Both the short-term and long-term interventions consisted of
center-based training that included both walking and upper-body
strength training conducted 3 times each week. Each session consisted
of four phases: a warm-up (5 min), an aerobic stimulus phase (30 to 35
min), an upper-extremity strength training phase (15 to 20 min), and a
cool-down period (5 min). The warm-up phase consisted of slow walking
and four calisthenic-type exercises: arm circles, trunk rotations,
shoulder and chest stretch, and side stretch. Participants were
instructed to walk at a rating of perceived dyspnea of 3 to 4 (moderate
to somewhat hard), based on the Borg9
categorical
scale.10
Participants were encouraged to work for the
entire 35 min within their THRR; however, individual adjustments were
made depending on abilities to meet the exercise goals. The
upper-extremity strength training program consisted of four gravity
resistance exercises designed to increase strength in the muscles of
the arms and the shoulder girdle. These exercises incorporated
movements such as extension of the arms overhead, with the participant
in a seated position, elbow flexion, horizontal flexion of the shoulder
with the participant lying supine, as well as shoulder elevation and
rotation. All exercises were performed using small hand weights.
Participants were asked to perform two sets of 10 repetitions for each
exercise, with a 1-min rest period between each set.
Statistical Analyses
The primary outcome measures of interest were the four domains
of the CRQ scores. Changes in preintervention scores from baseline to 3
months, as well as treatment and gender differences at the 18-month
assessment, were analyzed using analyses of covariance (adjusting for
baseline CRQ scores, age, and %FEV1 predicted).
Analyses were conducted using the SAS statistical package (Procedure
General Linear Model; SAS Institute; Cary, NC). Significance was
set at the 0.05 level for all tests. All results are presented as
adjusted means and SEM or as mean and SD.
Results
Demographic and medical information regarding the participants at the initial screening visit is shown in Table 1 . Inspection of these data reveals that the study sample was an older group of men and women who were overweight, relatively heterogeneous on income, and had mild-to-moderate disease. As expected, there were a number of comorbid conditions. For example, 41% of the participants in the short-term condition and 40% in the long-term condition had arthritis, and 41% of the participants in the short-term condition and 46% of individuals in the long-term condition had hypertension. Also, 39% of participants in the short-term condition and 34% of individuals in the long-term condition had heart disease.
Table 2 provides data pertinent to compliance with the intervention partitioned by gender. Statistics are provided for the entire sample from months 0 to 3 and for those randomized to long-term therapy for months 3 to 18. Variables listed include percent attendance and average exercise intensity. Inspection of these data reveals that the participants were compliant with the prescription to the aerobic phase of exercise therapy. For example, participants who were randomized to the long-term and short-term conditions demonstrated comparable attendance to exercise sessions conducted at the center from baseline to 3 months. Furthermore, Table 2 demonstrates that there was no evidence for gender differences within the two conditions.
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= 0.56). Similarly, for emotional function, the
long-term mean was higher for men than women ( = 0.61).
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The primary objectives of this study were: (1) to contrast
the effects of short-term vs long-term exercise therapy on the
disease-specific HRQL of patients with COPD, and (2) to explore the
potential moderating effect of gender on any observed differences
betweenthe two treatments. During the first 3 months of exercise
therapy, all participants experienced statistically significant
improvements in their CRQ scores, a disease-specific index of HRQL.
Interestingly, women reported more gains than men in the dyspnea
( = 0.85 vs = 0.49) and fatigue ( = 0.57 vs
= 0.53) domains of the CRQ. Haggerty and
colleagues11
also reported gender differences among
patients who participated in short-term PR. However, in their study,
effects were observed on the mastery and control subscales of the CRQ.
It is difficult to resolve the differences between our data and that of
Haggerty et al11
because the latter study involved
comprehensive PR, as opposed to exercise therapy alone. Also, the study
by Haggerty et al11
involved data from 10 different
centers. The exercise therapy in these centers ranged from 1 to 3 days
each week and lasted anywhere from 5 weeks to 12 weeks. Although this
phase of our study design did not have a control group for comparison,
our results are consistent with existing quantitative reviews of the
short-term PR literature.2
3
One unexpected trend in these
first 3 months of data concerns the failure of scores, on the emotional
functioning and mastery domains of the CRQ, to approach a change of one
half unit, an increment deemed by Lacasse and colleagues2
to be clinically significant. One explanation for this pattern in the
data is the fact that baseline scores for the emotional functioning and
mastery domains were more than a full unit higher than scores for
dyspnea and fatigue. In the study of psychological functioning,
baseline scores commonly influence the degree of change observed with
exercise interventions.12
The randomized component of the current study, which involved a
comparison of short-term (3 months) vs long-term (18 months) exercise
therapy, produced statistically significant effects on all scores of
the CRQ. In fact, the dyspnea scale approached clinical significance
( = 0.47), and the fatigue scale change was of a clinically
relevant magnitude ( = 0.53). Although these differences favor
long-term therapy, any interpretation of the differences between
long-term vs short-term in the CRQ must be qualified by the moderating
effect observed for gender. Specifically, examination of the adjusted
18-month CRQ data revealed that any advantage of long-term exercise
therapy, compared with the short-term therapy condition, was due to
benefits accrued by men and not women. The similarity in CRQ scores for
women randomized to either short-term or long-term exercise therapy was
striking. The largest difference between these conditions was only one
tenth of a unit for any of the CRQ domains, and the absolute scores
were similar to men in short-term therapy. By contrast, men in the
long-term group experienced an improvement in fatigue rate
of0.83 U and an enhancement in emotional function of 0.45 U compared
with men in short-term therapy.
Data concerning the mastery and dyspnea domains require additional discussion. Whereas men in the long-term condition received a clear benefit of 0.40 U in mastery compared with men in short-term therapy, there was no such effect for women. However, at 18 months, women in the short-term group reported the same level of mastery as women in the long-term group, an absolute value that was comparable to men in the long-term group. For some reason, women assigned to short-term therapy continued to improve their mastery scores for up to 18 months despite the lack of an active treatment program. Furthermore, it is interesting to recall that women made dramatic improvements in dyspnea scores during the first 3 months of treatment compared with men. These effects were not lost as a function of short-term exercise therapy. In fact, it took 18 months for men to improve their dyspnea scores to a level that was comparable to those of the women.
Taken collectively, the CRQ data demonstrate that long-term exercise therapy has little added benefit for women over short-term exercise therapy; however, men derive significant benefits from extended training. It is intriguing that women made more dramatic improvements in their dyspnea scores with 3 months of training than did men, whereas women appeared to be limited in their ability to enhance emotional functioning and mastery through exercise therapy alone. Although we cannot offer definitive explanations for these effects, several hypotheses come to mind. First, one might argue that, in the long-term condition, women didn’t adhere to the exercise prescription as closely as did the men. However, examination of data on the exercise attendance and intensity does not support such a hypothesis. Second, it is plausible that exercise alone is an insufficient form of rehabilitation for women. This could be tied to the fact that men value their physical function more than women do and thus derive more benefit from involvement in extended exercise therapy. In addition, drawing from the findings in cardiac rehabilitation literature, there is evidence to support the possibility that women may benefit more from rehabilitation that includes emotional support from staff members and social interaction, along with traditional exercise therapy.13 In general, the current study suggests that future research should consider testing the independent effects of various components of comprehensive PR on HRQL and should take seriously the moderating effects of gender in both the design and analysis of subsequent intervention research.
Footnotes
Abbreviations: CRQ = Chronic Respiratory Disease Questionnaire; HRQL = health-related quality of life; PR = pulmonary rehabilitation; RCT = randomized clinical trial; RHR = resting heart rate; THRR = training heart rate range
Supported by National Institutes of Health/National Institute on Aging postdoctoral training grant 5P60 AG10484–07 (Dr. Foy). Funding for the trial from which this article evolved was provided by grant HL 53755 from the National Heart, Lung, and Blood Institute. Funding was also provided by National Institutes of Health/National Institute on Aging grant P60 AG10484.
Received for publication March 23, 2000. Accepted for publication August 14, 2000.
References
This article has been cited by other articles:
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  M. T. Dransfield, G. R. Washko, M. G. Foreman, R. S. J. Estepar, J. Reilly, and W. C. Bailey Gender Differences in the Severity of CT Emphysema in COPD Chest, August 1, 2007; 132(2): 464 - 470. [Abstract] [Full Text] [PDF]
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A. L. Ries, G. S. Bauldoff, B. W. Carlin, R. Casaburi, C. F. Emery, D. A. Mahler, B. Make, C. L. Rochester, R. ZuWallack, and C. Herrerias Pulmonary Rehabilitation: Joint ACCP/AACVPR Evidence-Based Clinical Practice Guidelines Chest, May 1, 2007; 131(5_suppl): 4S - 42S. [Abstract] [Full Text] [PDF]
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 B. R. Celli Roger S. Mitchell Lecture. Chronic Obstructive Pulmonary Disease Phenotypes and Their Clinical Relevance Proceedings of the ATS, August 1, 2006; 3(6): 461 - 465. [Abstract] [Full Text] [PDF]
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D. Verrill, C. Barton, W. Beasley, and W. M. Lippard The Effects of Short-term and Long-term Pulmonary Rehabilitation on Functional Capacity, Perceived Dyspnea, and Quality of Life Chest, August 1, 2005; 128(2): 673 - 683. [Abstract] [Full Text] [PDF]
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 R. Antonelli-Incalzi, C. Imperiale, V. Bellia, F. Catalano, N. Scichilone, R. Pistelli, F. Rengo, and the SaRA investigators Do GOLD stages of COPD severity really correspond to differences in health status? Eur. Respir. J., September 1, 2003; 22(3): 444 - 449. [Abstract] [Full Text] [PDF]
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