Zullo, Melissa D. PhD, MPH, MA; Dolansky, Mary A. PhD, RN; Jackson, Leila W. PhD, MPH
Coronary artery disease is the leading cause of death and disability in the United States and globally. In the United States, there are 7.9 million survivors of myocardial infarction (MI), and every year 1.2 million Americans have a new or recurrent MI.1 Secondary prevention, including revascularization and medications to treat angina, lipidemia, and hypertension, has contributed to a decline in the mortality rate for coronary artery disease over the past 25 years.2,3 However, as medical interventions are maximized, the need for aggressive secondary prevention centering on behavior change and maintenance becomes evident.
Cardiac rehabilitation (CR) phase II programs are multifactorial, secondary prevention programs designed for people after hospitalization following a cardiac event or procedure. Compared with traditional CR programs, which were designed as return to work programs focusing on exercise, multifactorial programs include directed interventions aimed at behavior modification and risk reduction. The immediate benefits of CR have been well documented and include improvements in physical activity level and tolerance, blood pressure (BP), cholesterol, and mental health.4–8 Despite the concurrent behavior changes associated with CR, behavior maintenance after program completion has not been established.
Research on behavior maintenance after CR has focused on physical activity with few studies examining sustainability of nutrition behaviors and weight loss. The percentage of patients performing physical activity post-CR that meets national guidelines of 3 to 5 d/wk ranges from 42% at 2 months to 15% to 50% at 6 months to 25% at 1 year.9–12 Examination of nutrition behaviors post-CR has shown that patients receiving intensive dietary consultation have improved diet composition, including fruit and vegetable consumption, over those who received standard care.13,14 However, regardless of instruction, intervention patients consumed servings of vegetables that were smaller than standard portion sizes, and 1 year post-CR, consumption did not differ from that in the standard care group.
The majority of CR patients are overweight or obese,15 and few experience weight loss during the program. Failure to lose weight may be due to low energy expenditure in rehabilitation16 or the relatively short duration of the program. Monitoring weight loss after program completion is important to observe the effect of CR on long-term outcomes.
Time at which CR-associated behaviors begin to diminish has not been well documented. Information on long-term follow-up of CR-learned behaviors is needed to identify the time at which behavior performance decreases and when supplemental programming will be beneficial. The purpose of this research was to examine health behaviors, including fruit and vegetable consumption and physical activity, and body mass index (BMI) in relation to CR attendance and time since CR participation in respondents reporting a history of MI.
A cross-sectional analysis was performed using data from the 2003 Behavioral Risk Factor Surveillance System (BRFSS)17 to examine the association post-MI between CR attendance and health behaviors and CR attendance and BMI. The BRFSS is a random-digit-dialed, telephone-administered survey designed to monitor health conditions and behaviors. The sample consists of civilian, noninstitutionalized American adults 18 years or older. The BRFSS is supported by the Centers for Disease Control and Prevention and is administered annually by the 50 state health departments and those of the District of Columbia, Puerto Rico, Guam, and the US Virgin Islands. This protocol was reviewed and approved by the institutional review board.
The data year 2003 was the most recent that included questions on the variables of interest: coronary artery disease, rehabilitation attendance, age at first MI, and the health-behavior variables. In 2003, the cardiovascular disease module was asked of approximately 110,000 individuals in 23 states, the District of Columbia, and Puerto Rico. Respondents were asked whether a physician, a nurse, or other health professional ever told them they had a heart attack or MI; those with a positive response were eligible for analyses (n = 5,059). CR attendance was determined by asking respondents whether they went to outpatient rehabilitation after leaving the hospital. Respondents may have attended rehabilitation for MI, stroke, or both MI and stroke; therefore, those indicating a history of stroke (n = 3,011) or stroke and MI (n = 821) were excluded from analyses (Figure 1).
Eligibility was constrained to the first MI at age 31 or greater and within the previous 10 years (1993–2003) (n = 455). The sample was further limited to respondents providing information on the outcomes and potential confounders of interest. This resulted in a subpopulation size of 1,374. Of these, 463 (34%) persons attended CR.
CR attendance was based on self-report. Time since MI was created from current age and age at event. This variable was used as a proxy to represent time since CR attendance, defined a priori as less than 1.0 year, 1.0 year or more to less than 2.0 years, 2.0 years or more to less than 5.0 years, and 5.0 years or more to 10.0 years.
Outcomes included fruit and vegetable consumption, physical activity level, and BMI. Fruit and vegetable consumption was determined by asking respondents how often they ate fruits and vegetables/day. The BRFSS summary index, ranging from “less than once/ day or never” to “5 or more times/day,” was used for analyses. Fruit and vegetable consumption was dichotomized as “meets” or “does not meet” national recommendations for 5 or more servings/day.
Physical activity level was determined by asking how many days/week respondents participated in moderate activity for 10 min/d or more. Respondents indicating participation in moderate physical activity for 10 min/d or more were asked on days when they performed moderate activities for 10 minutes or more at a time how much total time they spent participating in the activities. A similar line of questioning was used for vigorous activity. The BRFSS included a 5-category physical activity variable created from these questions, which ranged from “meeting recommendations for moderate and vigorous physical activity” to “no moderate or vigorous physical activity.” The 5-category physical activity variable was used to determine meeting national recommendations18,19 for moderate and/or vigorous physical activity in adults. For this research, physical activity was dichotomized as “meets” or “does not meet” recommendations for moderate and/or vigorous physical activity. Moderate physical activity was defined as performing moderate physical activity 5 d/wk or more for 30 min/d or more, and vigorous physical activity was defined as performing vigorous physical activity 3 d/wk or more for 20 min/d or more. Respondents met guidelines if they performed “both moderate and vigorous,” “moderate only,” or “vigorous only” physical activity. The BRFSS-calculated BMI variable was categorized as underweight to normal weight (≤24.9), overweight (25.0–29.9), or obese (≥30.0).
Variables examined as potential confounders included any physical activity in the last 30 days excluding regular job (no/yes); smoking status (never, former, current); cholesterol checked (≤1 year or >1 year); use of BP medications (no/yes); and demographic variables including race-ethnicity (white non-Hispanic, black non-Hispanic, and other); education, representing socioeconomic status (less than high school education or high school education or more); marital status (not married or married); gender; and current age and age at first MI.
Statistical analyses were performed in STATA, Version 9.2 (StataCorp LP, College Station, Texas), software using sample weights for the complex survey design and a subpopulation representing those respondents described above. Data were examined for outliers, normality, and correlations. Variables correlated at greater than 0.40 were excluded from analyses, which removed simultaneous use of age at MI and current age (r = 0.97). CR attendees and nonattendees were compared using χ2 and Student t tests (Table 1). Potential predictors/confounders significant at P value of .20 or less and borderline significant predictors/ confounders thought to be associated with the outcome were retained for multivariable modeling. Associations between CR attendance and the outcome variables were examined using logistic or polytomous logistic regression. Proportional odds assumptions were verified. Factors that changed the association between CR attendance and the outcome by more than 10% remained in the model as confounders.
The association of CR attendance with time post-CR was examined in stratified analyses. The full model for each outcome variable in multivariable regression was stratified by 4 time points since MI: less than 1.0 year, 1.0 year or more to less than 2.0 years, 2.0 years or more to less than 5.0 years, and 5.0 years or more to 10.0 years. Logistic or polytomous logistic regression were used to examine the association between CR attendance and the outcome variables stratified by time.
Overall, 34% of eligible individuals in this population attended rehabilitation after first MI (Table 1). CR attendees were 64% male and nonattendees were 57% male (P = .12). CR attendees were more likely to meet fruit and vegetable (attendees: 28%, nonattendees: 19%; P = .02) and physical activity guidelines (attendees: 41%, nonattendees: 30%; P = .01), compared with nonattendees. BMI did not differ between the groups (P = .22); however, a greater proportion of attendees had normal BMI (25%) as compared with nonattendees (20%). Differences were observed in the following health behaviors and demographics for attendees compared with nonattendees: any physical activity in the last 30 days (P < .01), smoking (P = .01), cholesterol check (P < .01), age at survey (P = .02), and age at first MI (P < .001). No difference was observed between CR attendance and mean time since MI as a continuous variable (attendees, M = 4.3 [±3.1] years and nonattendees, M = 4.4 [±3.1] years; P = .63) or when time since MI was categorized into 4 postCR time points (P = .34). No difference was observed in CR attendance by race, education, gender, marital status, or use of BP medications.
In weighted, univariate analyses, significant predictors varied for each outcome. Respondents who attended CR were 67% more likely to meet fruit and vegetable consumption guidelines (95% confidence interval, CI: 1.1–2.6) at time of survey. Significant predictors in the fruit and vegetable model included any physical activity in last 30 days, meeting physical activity guidelines, BMI, BP medications, smoking status, gender, mean age at first MI, and time since MI. Respondents attending CR were 59% more likely to meet physical activity guidelines (95% CI: 1.1–2.3) at time of survey. Significant predictors in the physical activity model included any physical activity in the last 30 days, meeting fruit and vegetable guidelines, cholesterol check, BP medications, race/ethnicity, education, and mean age at first MI. CR attendees were less likely to be overweight or obese (odds ratio, OR = 0.81, 95% CI: 0.52–1.2, and OR = 0.67, 95% CI: 0.44–1.0, respectively) at time of survey. Significant predictors in the BMI model included any physical activity in the last 30 days, meeting fruit and vegetable guidelines, cholesterol check, race/ethnicity, smoking and marital status, education, and mean age at first MI.
In weighted, multivariable analyses, respondents who attended CR were 69% more likely to meet fruit and vegetable guidelines than were those who did not attend CR after controlling for smoking status and gender (Table 2). Respondents who attended CR were 46% more likely to meet physical activity guidelines than were those who did not attend CR when controlling for any physical activity in the past 30 days, smoking status, and mean age at first MI; however, this association was not significant (P = .05). CR attendance showed a protective, yet nonsignificant effect (ie, no association) on BMI for overweight and obese after adjusting for smoking status, gender, education, and age at first MI.
Time Since CR Analyses
In stratified analyses, attendees (n = 34) were more than 4 times as likely to meet fruit and vegetable guidelines as nonattendees (n = 61) when CR was attended within the past year (OR 4.64, CI: 1.03–20.95) after controlling for smoking status, BMI, and gender (results not shown). Between 1 and 2 years, there was a protective, yet nonsignificant effect (ie, no association) of CR with attendees (n = 68) being more than 2 times as likely to meet fruit and vegetable consumption guidelines (OR = 2.5, 95% CI: 0.88–7.18) compared to nonattendees (n = 133) when controlling for smoking. The protective, nonsignificant effect of CR attendance (attendees: n = 164, nonattendees: n = 309) on fruit and vegetable consumption continued between 2 and less than 5 years postCR (OR = 1.85, 95% CI: 0.99–3.47).
Meeting physical activity guidelines was not significantly associated with CR attendance, and no association was observed in stratified analyses. Between years 1 and 2, attendees were 75% less likely to be overweight than were nonattendees (95% CI: 0.08–0.73) when controlling for any physical activity in the past 30 days and age at first MI. Between year 2 and 5, attendees were 59% less likely to be obese than were nonattendees (95% CI: 0.20–0.85) when controlling for smoking status, gender, and age at first MI.
In this national sample of adults indicating a history of MI within the past 10 years, 34% attended CR after their first MI. This is consistent with national samples of CR attendance.8,20,21 Overall, CR attendees were 70% more likely to meet fruit and vegetable consumption guidelines than were nonattendees when controlling for other variables in the model. In time-stratified analyses, the association continued when rehabilitation was attended within the past year; however, there was no association after 1 year. Increased fruit and vegetable consumption to manage lipids and body weight after MI is recommended by the American College of Cardiology and the American Heart Association.22 CR guidelines recommend nutrition counseling,23–25 and multifaceted programs will ideally evaluate nutrition and provide appropriate interventions to address deficiencies. To enhance maintenance, supplemental programming at or near 1 year post-CR may assist patients in maintaining healthy nutrition.
In this research, CR attendance showed a protective, nonsignificant effect on meeting physical activity guidelines in both multivariable and time-stratified analyses, an observation that is supported in the CR literature.9–11,26 However, behavioral interventions directed at physical activity maintenance have demonstrated efficacy. Patients participating in interventions based on action planning and/or coping planning,11 or lifestyle modification programs such as CHANGE,27 have increased and maintained physical activity levels when compared with those receiving standard care in CR. Sustained physical activity may also be achieved through CR maintenance programs (eg, phase III or IV CR). Bock et al9 observed that participants and graduates of phase III CR were more likely to currently participate in vigorous levels of physical activity (96% and 70%, respectively; P < .01) than were those who participated only in phase II. Because of space and staff limitations, CR programs may not be able to accommodate patients who will benefit from continued supervision. Consequently, alternatives to activity maintenance must be explored.
CR attendance showed a protective, yet nonsignificant association with current BMI, with a greater proportion of attendees in the overweight category (42%, n = 201) than in the obese category (32.6%, n = 143). When stratified by time since CR, between year 1 and 2 postrehabilitation, attendees were 75% less likely to be overweight than were nonattendees. Between years 2 and 5, attendees were 59% less likely to be obese than were nonattendees. Because of the cross-sectional nature of this study, it cannot be determined whether this association is a result of weight loss post-CR, whether respondents were of a lower/higher BMI at any other time point, or whether obese patients are less likely to attend CR. To increase weight loss in overweight and obese patients, CR providers must emphasize increased caloric expenditure. The American College of Sports Medicine recommends a minimum of 150 minutes of moderate intensity physical activity/week to observe modest weight loss with the recognition that increased durations of 250 to 300 min/wk may result in greater weight loss.28 When appropriate, CR programs will recommend increased energy expenditure.
The strengths of this study are that it was conducted on a nationally representative sample of adults and that postMI health-behavior performance and BMI were described both overall and at specific periods postCR. Long-term studies of health behaviors postCR are limited, and the current research, although restricted in its ability to examine detailed dietary behaviors and comorbid conditions, confirms the results of previous short-term studies.
Because this research used data from a cross-sectional, telephone-administered survey, there are limitations to the research questions that can be asked and the conclusions that can be drawn. The first limitation is in the self-reported nature of the data. Self-reported physical activity and nutrition are often overreported, which may have affected the results of these analyses29,30; however, it is not known if the reporting had a differential effect on the associations observed in this research. In other words, overreporting may have occurred in both CR attendees and nonattendees. Second, observed differences may be due to healthier patients self-selecting into CR, introducing a potential selection bias and suggesting that healthy behaviors and BMI may be due to historical performance rather than CR-learned behaviors. Conversely, one could argue that healthier patients are more likely to maintain behaviors postCR; yet, there was little evidence of maintenance in this research. Third, although time postCR analyses were conducted, current behaviors may have differed at other times. Furthermore, because this research examined a 10-year period, it crossed the time when CRs were moving from exercise-only to multifactorial programs; therefore, nutrition behaviors, one focus in contemporary programs, may be more representative of recent CR attendance.
Limitations to this research, related to the BRFSS cardiovascular disease module, are lack of information on the number of CR sessions attended, current participation in CR, or participation in CR for a secondary or more recent event. Furthermore, the inability to control for individual CR program practices, detailed nutrition, comorbidity, and historical health-related information was a limitation that may have affected the results of this research.
CR attendees generally perform health behaviors at recommended levels during CR; however, the results of this research are consistent with research showing that after CR completion, behaviors are not maintained.6,9,11 Prospective studies, of health behaviors and BMI postCR, are necessary to describe maintenance of multiple health behaviors. These studies will identify points in time when health behaviors become inconsistent and diminish and interventions to maintain health behaviors past these time points. Identification of these factors will assist CR programs in providing effective programming aimed at long-term maintenance of health in the patient postCR.
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