CARDIAC REHABILITATION
Examining the Steps-Per-Day Trajectories of Cardiac Rehabilitation Patients A LATENT CLASS GROWTH ANALYSIS PERSPECTIVE
Chris M. Blanchard, PhD; Nicholas Giacomantonio, MD; Renee Lyons, PhD; Cleo Cyr, RN; Ryan E. Rhodes, PhD; Robert D. Reid, PhD; J. C. Spence, PhD; Kerry R. McGannon, PhD
■ PURPOSE: Research suggests that cardiac rehabilitation (CR) patients need to engage in at least 6500 steps per day to obtain health benefits. Unfortunately, very little is known about the steps-per-day trajectories of these patients and whether the demographic, clinical, and CR program characteristics are similar for these trajectories.
K E Y
■ METHODS: Patients (n = 235) completed a questionnaire assessing demographic and clinical variables upon entry to CR and subsequently wore a pedometer for 7 days at the end of CR, and 3, 6, and 9 months after completing CR.
steps per day
■ RESULTS: Latent class growth analyses showed that 3 classes of patients emerged that were termed nonadherers (averaged ∼3112 steps per day at the end of CR and remained stable up to 9 months after CR), significant decliners (averaged ∼7010 steps per day at the end of CR and steadily declined after CR), and optimal adherers (averaged ∼10 700 steps per day and remained stable after CR). Logistic regressions showed that nonadherers were more likely to be obese, have at least 1 comorbidity, and a lower exercise capacity compared with the significant decliners/optimal adherers. ■ CONCLUSIONS: Distinct steps-per-day trajectories exist for CR patients that are partially distinguished by demographic and clinical variables.
W O R D S
cardiac rehabilitation latent class growth analysis
Author Affiliations: Department of Medicine, Division of Cardiology (Drs Blanchard and Giacomantonio), Dalhousie University, Halifax, Nova Scotia, Canada; Bridgepoint Health, Toronto, Ontario, Canada (Dr Lyons); New Brunswick Heart Centre, Saint John, New Brunswick, Canada (Ms Cyr); Behavioral Medicine Laboratory, Faculty of Education, University of Victoria, Victoria, British Columbia, Canada (Dr Rhodes); Minto Prevention and Rehabilitation Centre, Ottawa Heart Institute, Ottawa, Ontario, Canada (Dr Reid); Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada (Dr Spence); and School of Human Kinetics, Laurentian University, Sudbury, Ontario, Canada (Dr McGannon). The authors declare no conflicts of interest. Correspondence: Chris M. Blanchard, PhD, Centre for Clinical Research, Dalhousie University, Room 205, 5790 University Ave, Halifax, NS B3H 1V7, Canada ([email protected]). DOI: 10.1097/HCR.0000000000000031
It is recommended that patients with heart disease accumulate 30 minutes of moderate to vigorous physical activity (PA) on at least 5 days of the week.1 Unfortunately,
less than 55% of patients are meeting these recommendations during and after cardiac rehabilitation (CR),2-5 suggesting that PA adherence is a problem. However,
106 / Journal of Cardiopulmonary Rehabilitation and Prevention 2014;34:106-113
www.jcrpjournal.com
Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
JCRP-D-13-00072R2.indd 106
14/02/14 11:34 AM
these studies used self-reported PA measures, whereas the use of objective measures (eg, pedometers) has been encouraged for patients with heart disease to obtain more valid and reliable PA assessments.6,7 In the context of CR, where resources tend to be scarce, an affordable way to obtain an objective PA assessment is to use pedometers.8 To date, 3 studies during CR have shown that patients average 8658 steps per day on CR days and 5364 steps per day on non-CR days,9-11 whereas patients averaged 6749 steps per day 6 months after CR.12 There are several concerns relative to these studies, however. First, although informative, 2 of these studies9,10 did not standardize the timing of recruitment, making it difficult to discern how active patients were at a given time point (eg, at the end of CR). Second, only 1 study12 assessed steps per day after CR only in patients with myocardial infarction. Whether similar steps per day after CR are present in a more heterogeneous sample remains unknown. Third, none of the studies measured PA during and after CR with the same sample. As a result, it occurs that the use of an objective PA assessment with a heterogeneous sample of CR patients might provide important insights regarding the stability of PA for these patients. The first purpose of this study was to examine the steps-per-day growth trajectories of CR patients from the end of CR to 3, 6, and 9 months after completing CR, using latent class growth analysis (LCGA). This approach was chosen because traditional growth-modeling approaches (eg, repeated-measure analysis of variance) assume patients come from a single population and that a single growth trajectory can adequately approximate an entire population.13 However, a recent study14 in patients with heart disease not attending CR challenged this approach by identifying 2 distinct classes (subgroups) of patients using self-reported PA data. The first class (ie, ∼20% of the sample) averaged 143 minutes per day of PA at baseline, after which the PA levels significantly declined to 76 minutes per day 1 year after hospitalization. The second class (ie, ∼80% of the sample) averaged 11 minutes per day of PA at baseline, which significantly increased to 21 minutes per day at 1 year. Whether similar classes of patients exist in CR patients using an objective PA measure remains unknown. The second purpose of the present study was to identify key predictors of class membership. This is particularly important to identify patients who may be at risk for inactivity (ie, if an inactive steps-per-day trajectory emerges).
METHODS Ten programs received ethical approval, although 2 did not complete participation and informed their www.jcrpjournal.com
respective ethics boards. The remaining 8 programs (ie, 5 in New Brunswick and 3 in Nova Scotia, Canada) combined medically supervised PA with nutrition and behavior modification education to reduce risk factors associated with heart disease. The programs ranged in duration (ie, 6, 10, or 12 weeks), frequency of PA sessions (ie, once versus twice per week), and location (ie, 2 community-based and 6 hospital-based).
Participants Patients were eligible to participate if they were currently participating in CR, were ≥18 years of age, could read and write English, and provide informed consent. Patients were excluded if they were unable to ambulate independently or failed to complete at least 1 pedometer assessment.
Measures Patient characteristics Demographic characteristics included self-reported age, gender, education, marital status, race, employment, and income. Clinical characteristics (ie, whether or not it was the patient first cardiac event; height, weight, and body mass index; and the presence or absence of diabetes, stroke, lung disease, arthritis, cancer, circulation problems, back pain, hip pain, knee pain, and foot pain) were obtained via selfreport and chart review and were summed to form a comorbidity score. Each site completed a standardized form to provide the diagnosis and baseline stress test scores in metabolic equivalents (METS). Finally, the CR program characteristics (ie, program length, program frequency, patient adherence to PA sessions, and distance to CR from the patient homes) were recorded via a standardized form that was calculated in ArgGIS 10.1 (ESRI Inc, Toronto, Ontario, Canada).
Self-reported PA Physical activity was measured via a modified version of the Godin Leisure-Time Exercise Questionnaire.15,16 Patients were asked, (a) “How many days in a typical week out of the past 3 months did you do light (eg, walking) exercises for at least 10 minutes at a time? and (b) “On the days when you did light exercises, how much total time on average did you spend per day doing these light exercise(s)?” The same 2 questions assessed the frequency and duration of moderate (eg, brisk walking and easy cycling) and vigorous (eg, running and jogging) activities. The frequency and duration for each intensity were multiplied to obtain the total minutes of activity per week within each intensity. For the current study, we summed the moderate and vigorous minutes to obtain the total Steps-Per-Day Trajectories / 107
Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
JCRP-D-13-00072R2.indd 107
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minutes per week of moderate to vigorous PA, which has been validated in patients with heart disease.14
Steps per day The number of steps was assessed using the Yamax DIGI-WALKER (San Antonio, TX), which has been shown to be a valid and reliable pedometer17 (ie, accurately measuring the number of steps taken during a 400-m walk) and has been used in other trials in patients with heart disease.18 Before wearing, the pedometer was programmed for the patient stride length and weight to ensure accuracy of the step counts obtained. Patients were asked to wear the pedometer on their right hip for all waking hours of the day for 7 consecutive days and record their daily steps in a logbook at the end of each day. The total number of steps was added across the 7 days and divided by 7 to obtain a steps-per-day outcome variable.
Procedure On receiving ethical approval at each site, patient charts were reviewed for eligibility on program entry. Eligible patients were approached by a CR staff member to ask for their permission to have a research assistant (RA) approach them about the study. Patients who agreed were approached by the RA in the third week of their program. At that time, patients not interested were thanked for their time and were asked to complete a 1-page nonparticipant questionnaire. Those who agreed were given a consent form and baseline questionnaire that included the self-reported demographic and clinical questions to complete that day (ie, either on site or at home). Patients who took the documents home returned them at their next CR class. At the end of CR (ie, within the last 2 weeks of program completion), patients were asked to complete the same questionnaire in addition to wearing a pedometer for a 7-day period. Patients recorded their daily steps in a logbook and returned their study materials during the following week's class. Finally, patients were asked to complete the same questionnaire and wear the pedometer 3, 6, and 9 months after completing CR. For each assessment, patients were contacted by the RA to provide them with the study materials (ie, in person at the CR site or via the mail), after which an arrangement was made to obtain the completed materials at the CR site or receive them via the mail in a postage-paid envelope.
Analytical Plan Recruitment rates were calculated followed by between-subject analyses of variance and χ2 analyses to determine potential differences between participants and nonparticipants, after which the baseline
demographic, clinical, and program characteristics were generated. Next, a series of LCGAs19 was conducted in MPLUS 6.1 using full information maximum likelihood estimation to include all patients with at least 1 pedometer assessment. A single-class model was specified first with a latent intercept growth factor (ie, steps per day at the end of CR) and a latent slope growth factor (0, end of CR; 3, 3 months after CR; 6, 6 months after CR; and 9, 9 months after CR) to reflect the monthly change in steps per day. Next, a quadratic term was added to test for its necessity in the model. The same procedure was then used to examine 2-, 3-, and 4-class models. To identify the number of classes (objective #1), the Bayesian Information Criterion, the Bootstrapped Likelihood Ratio Test, and entropy indices were used. When comparing a 2-class versus single-class model, for example, a change in the Bayesian Information Criterion >10, higher entropy value (near 1.0), and a Bootstrapped Likelihood Ratio Test P < .05 would be considered as evidence favoring the 2-class over the single-class model.20 Once the final number of classes was generated, a series of χ2 analyses was conducted in SPSS 20.0 to determine potential demographic, clinical, and program differences across the classes. All significant variables were then entered into a series of logistic regressions to delineate the most important class membership predictors (objective #2).
RESULTS There were 606 patients deemed eligible, and 235 patients agreed to participate and completed at least 1 pedometer assessment. The nonparticipants were similar in age (F1,432= 1.78, P = .18), gender (χ21= 0.46, P = .49), and self-reported minutes of PA (F1,378= 0.07, P = .79) compared with participants. Of the 235 patients who participated in the study, 149 completed their assessment 3 months after CR, 144 completed 6 months after CR, and 150 completed 9 months after CR. Detailed demographics for the 235 patients are presented in Table 1. In terms of the LCGAs, results indicated that the 4-class model showed the best model fit (Table 2). However, the first class had only 12 patients, making subsequent analytical comparisons difficult. Therefore, the 3-class model was chosen. The first class (ie, nonadherers) comprised 27.2% of the sample and averaged 3113 steps per day at the end of CR, which remained stable up to 9 months after CR. The second class (ie, optimal adherers) comprised 27.4% of the sample and averaged 10 609 steps per day at the end of CR that remained stable up to 9 months after CR. The third class (ie, 45.4%) averaged 7011 steps per
108 / Journal of Cardiopulmonary Rehabilitation and Prevention 2014;34:106-113
www.jcrpjournal.com
Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
JCRP-D-13-00072R2.indd 108
14/02/14 11:34 AM
T a b l e 1 • Descriptive Statistics by Class and χ2 Comparisons by Class Nonadherers (Class 1)
Optimal Adherers (Class 2)
Significant Decliners (Class 3)
Examining the Steps-Per-Day Trajectories of Cardiac Rehabilitation Patients A LATENT CLASS GROWTH ANALYSIS PERSPECTIVE
Chris M. Blanchard, PhD; Nicholas Giacomantonio, MD; Renee Lyons, PhD; Cleo Cyr, RN; Ryan E. Rhodes, PhD; Robert D. Reid, PhD; J. C. Spence, PhD; Kerry R. McGannon, PhD
■ PURPOSE: Research suggests that cardiac rehabilitation (CR) patients need to engage in at least 6500 steps per day to obtain health benefits. Unfortunately, very little is known about the steps-per-day trajectories of these patients and whether the demographic, clinical, and CR program characteristics are similar for these trajectories.
K E Y
■ METHODS: Patients (n = 235) completed a questionnaire assessing demographic and clinical variables upon entry to CR and subsequently wore a pedometer for 7 days at the end of CR, and 3, 6, and 9 months after completing CR.
steps per day
■ RESULTS: Latent class growth analyses showed that 3 classes of patients emerged that were termed nonadherers (averaged ∼3112 steps per day at the end of CR and remained stable up to 9 months after CR), significant decliners (averaged ∼7010 steps per day at the end of CR and steadily declined after CR), and optimal adherers (averaged ∼10 700 steps per day and remained stable after CR). Logistic regressions showed that nonadherers were more likely to be obese, have at least 1 comorbidity, and a lower exercise capacity compared with the significant decliners/optimal adherers. ■ CONCLUSIONS: Distinct steps-per-day trajectories exist for CR patients that are partially distinguished by demographic and clinical variables.
W O R D S
cardiac rehabilitation latent class growth analysis
Author Affiliations: Department of Medicine, Division of Cardiology (Drs Blanchard and Giacomantonio), Dalhousie University, Halifax, Nova Scotia, Canada; Bridgepoint Health, Toronto, Ontario, Canada (Dr Lyons); New Brunswick Heart Centre, Saint John, New Brunswick, Canada (Ms Cyr); Behavioral Medicine Laboratory, Faculty of Education, University of Victoria, Victoria, British Columbia, Canada (Dr Rhodes); Minto Prevention and Rehabilitation Centre, Ottawa Heart Institute, Ottawa, Ontario, Canada (Dr Reid); Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada (Dr Spence); and School of Human Kinetics, Laurentian University, Sudbury, Ontario, Canada (Dr McGannon). The authors declare no conflicts of interest. Correspondence: Chris M. Blanchard, PhD, Centre for Clinical Research, Dalhousie University, Room 205, 5790 University Ave, Halifax, NS B3H 1V7, Canada ([email protected]). DOI: 10.1097/HCR.0000000000000031
It is recommended that patients with heart disease accumulate 30 minutes of moderate to vigorous physical activity (PA) on at least 5 days of the week.1 Unfortunately,
less than 55% of patients are meeting these recommendations during and after cardiac rehabilitation (CR),2-5 suggesting that PA adherence is a problem. However,
106 / Journal of Cardiopulmonary Rehabilitation and Prevention 2014;34:106-113
www.jcrpjournal.com
Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
JCRP-D-13-00072R2.indd 106
14/02/14 11:34 AM
these studies used self-reported PA measures, whereas the use of objective measures (eg, pedometers) has been encouraged for patients with heart disease to obtain more valid and reliable PA assessments.6,7 In the context of CR, where resources tend to be scarce, an affordable way to obtain an objective PA assessment is to use pedometers.8 To date, 3 studies during CR have shown that patients average 8658 steps per day on CR days and 5364 steps per day on non-CR days,9-11 whereas patients averaged 6749 steps per day 6 months after CR.12 There are several concerns relative to these studies, however. First, although informative, 2 of these studies9,10 did not standardize the timing of recruitment, making it difficult to discern how active patients were at a given time point (eg, at the end of CR). Second, only 1 study12 assessed steps per day after CR only in patients with myocardial infarction. Whether similar steps per day after CR are present in a more heterogeneous sample remains unknown. Third, none of the studies measured PA during and after CR with the same sample. As a result, it occurs that the use of an objective PA assessment with a heterogeneous sample of CR patients might provide important insights regarding the stability of PA for these patients. The first purpose of this study was to examine the steps-per-day growth trajectories of CR patients from the end of CR to 3, 6, and 9 months after completing CR, using latent class growth analysis (LCGA). This approach was chosen because traditional growth-modeling approaches (eg, repeated-measure analysis of variance) assume patients come from a single population and that a single growth trajectory can adequately approximate an entire population.13 However, a recent study14 in patients with heart disease not attending CR challenged this approach by identifying 2 distinct classes (subgroups) of patients using self-reported PA data. The first class (ie, ∼20% of the sample) averaged 143 minutes per day of PA at baseline, after which the PA levels significantly declined to 76 minutes per day 1 year after hospitalization. The second class (ie, ∼80% of the sample) averaged 11 minutes per day of PA at baseline, which significantly increased to 21 minutes per day at 1 year. Whether similar classes of patients exist in CR patients using an objective PA measure remains unknown. The second purpose of the present study was to identify key predictors of class membership. This is particularly important to identify patients who may be at risk for inactivity (ie, if an inactive steps-per-day trajectory emerges).
METHODS Ten programs received ethical approval, although 2 did not complete participation and informed their www.jcrpjournal.com
respective ethics boards. The remaining 8 programs (ie, 5 in New Brunswick and 3 in Nova Scotia, Canada) combined medically supervised PA with nutrition and behavior modification education to reduce risk factors associated with heart disease. The programs ranged in duration (ie, 6, 10, or 12 weeks), frequency of PA sessions (ie, once versus twice per week), and location (ie, 2 community-based and 6 hospital-based).
Participants Patients were eligible to participate if they were currently participating in CR, were ≥18 years of age, could read and write English, and provide informed consent. Patients were excluded if they were unable to ambulate independently or failed to complete at least 1 pedometer assessment.
Measures Patient characteristics Demographic characteristics included self-reported age, gender, education, marital status, race, employment, and income. Clinical characteristics (ie, whether or not it was the patient first cardiac event; height, weight, and body mass index; and the presence or absence of diabetes, stroke, lung disease, arthritis, cancer, circulation problems, back pain, hip pain, knee pain, and foot pain) were obtained via selfreport and chart review and were summed to form a comorbidity score. Each site completed a standardized form to provide the diagnosis and baseline stress test scores in metabolic equivalents (METS). Finally, the CR program characteristics (ie, program length, program frequency, patient adherence to PA sessions, and distance to CR from the patient homes) were recorded via a standardized form that was calculated in ArgGIS 10.1 (ESRI Inc, Toronto, Ontario, Canada).
Self-reported PA Physical activity was measured via a modified version of the Godin Leisure-Time Exercise Questionnaire.15,16 Patients were asked, (a) “How many days in a typical week out of the past 3 months did you do light (eg, walking) exercises for at least 10 minutes at a time? and (b) “On the days when you did light exercises, how much total time on average did you spend per day doing these light exercise(s)?” The same 2 questions assessed the frequency and duration of moderate (eg, brisk walking and easy cycling) and vigorous (eg, running and jogging) activities. The frequency and duration for each intensity were multiplied to obtain the total minutes of activity per week within each intensity. For the current study, we summed the moderate and vigorous minutes to obtain the total Steps-Per-Day Trajectories / 107
Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
JCRP-D-13-00072R2.indd 107
14/02/14 11:34 AM
minutes per week of moderate to vigorous PA, which has been validated in patients with heart disease.14
Steps per day The number of steps was assessed using the Yamax DIGI-WALKER (San Antonio, TX), which has been shown to be a valid and reliable pedometer17 (ie, accurately measuring the number of steps taken during a 400-m walk) and has been used in other trials in patients with heart disease.18 Before wearing, the pedometer was programmed for the patient stride length and weight to ensure accuracy of the step counts obtained. Patients were asked to wear the pedometer on their right hip for all waking hours of the day for 7 consecutive days and record their daily steps in a logbook at the end of each day. The total number of steps was added across the 7 days and divided by 7 to obtain a steps-per-day outcome variable.
Procedure On receiving ethical approval at each site, patient charts were reviewed for eligibility on program entry. Eligible patients were approached by a CR staff member to ask for their permission to have a research assistant (RA) approach them about the study. Patients who agreed were approached by the RA in the third week of their program. At that time, patients not interested were thanked for their time and were asked to complete a 1-page nonparticipant questionnaire. Those who agreed were given a consent form and baseline questionnaire that included the self-reported demographic and clinical questions to complete that day (ie, either on site or at home). Patients who took the documents home returned them at their next CR class. At the end of CR (ie, within the last 2 weeks of program completion), patients were asked to complete the same questionnaire in addition to wearing a pedometer for a 7-day period. Patients recorded their daily steps in a logbook and returned their study materials during the following week's class. Finally, patients were asked to complete the same questionnaire and wear the pedometer 3, 6, and 9 months after completing CR. For each assessment, patients were contacted by the RA to provide them with the study materials (ie, in person at the CR site or via the mail), after which an arrangement was made to obtain the completed materials at the CR site or receive them via the mail in a postage-paid envelope.
Analytical Plan Recruitment rates were calculated followed by between-subject analyses of variance and χ2 analyses to determine potential differences between participants and nonparticipants, after which the baseline
demographic, clinical, and program characteristics were generated. Next, a series of LCGAs19 was conducted in MPLUS 6.1 using full information maximum likelihood estimation to include all patients with at least 1 pedometer assessment. A single-class model was specified first with a latent intercept growth factor (ie, steps per day at the end of CR) and a latent slope growth factor (0, end of CR; 3, 3 months after CR; 6, 6 months after CR; and 9, 9 months after CR) to reflect the monthly change in steps per day. Next, a quadratic term was added to test for its necessity in the model. The same procedure was then used to examine 2-, 3-, and 4-class models. To identify the number of classes (objective #1), the Bayesian Information Criterion, the Bootstrapped Likelihood Ratio Test, and entropy indices were used. When comparing a 2-class versus single-class model, for example, a change in the Bayesian Information Criterion >10, higher entropy value (near 1.0), and a Bootstrapped Likelihood Ratio Test P < .05 would be considered as evidence favoring the 2-class over the single-class model.20 Once the final number of classes was generated, a series of χ2 analyses was conducted in SPSS 20.0 to determine potential demographic, clinical, and program differences across the classes. All significant variables were then entered into a series of logistic regressions to delineate the most important class membership predictors (objective #2).
RESULTS There were 606 patients deemed eligible, and 235 patients agreed to participate and completed at least 1 pedometer assessment. The nonparticipants were similar in age (F1,432= 1.78, P = .18), gender (χ21= 0.46, P = .49), and self-reported minutes of PA (F1,378= 0.07, P = .79) compared with participants. Of the 235 patients who participated in the study, 149 completed their assessment 3 months after CR, 144 completed 6 months after CR, and 150 completed 9 months after CR. Detailed demographics for the 235 patients are presented in Table 1. In terms of the LCGAs, results indicated that the 4-class model showed the best model fit (Table 2). However, the first class had only 12 patients, making subsequent analytical comparisons difficult. Therefore, the 3-class model was chosen. The first class (ie, nonadherers) comprised 27.2% of the sample and averaged 3113 steps per day at the end of CR, which remained stable up to 9 months after CR. The second class (ie, optimal adherers) comprised 27.4% of the sample and averaged 10 609 steps per day at the end of CR that remained stable up to 9 months after CR. The third class (ie, 45.4%) averaged 7011 steps per
108 / Journal of Cardiopulmonary Rehabilitation and Prevention 2014;34:106-113
www.jcrpjournal.com
Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
JCRP-D-13-00072R2.indd 108
14/02/14 11:34 AM
T a b l e 1 • Descriptive Statistics by Class and χ2 Comparisons by Class Nonadherers (Class 1)
Optimal Adherers (Class 2)
Significant Decliners (Class 3)
