Metabolic syndrome, defined as having 3 or more of the following 5 factors: abdominal obesity, elevated blood pressure, triglyceride, fasting plasma glucose, and decreased high-density lipoprotein cholesterol (HDL-C) level according to National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATP III) report, is increasing worldwide.1 Similar to Western countries, the prevalence of metabolic syndrome has sharply increased in Korea over the past few decades because of behaviors such as high lipid diet and sedentary lifestyle that have been fueled in part by the nation's rapid socioeconomic growth.2-4 Differences in the prevalence of metabolic syndrome have been reported in previous studies assessing a variety of population characteristics. For example, prevalence is increased in the elderly5-7 and patients with chronic diseases such as diabetes.3 Using the NCEP-ATP III criteria, age-adjusted prevalence among adults 19 years or older was 26.1% in 2005 according to a Korean National Health and Nutrition Examination Survey,8 compared with 24.1% in the United States.9
Metabolic syndrome causes a high risk of cardiovascular disease (CVD) and type 2 diabetes.10 Metabolic syndrome is accompanied by a lifelong 2-fold increased risk of CVD and a 5-fold increased risk of diabetes.11,12 The primary approach for preventing or reducing CVD risk involves lifestyle modifications, which include exercise, nutrition/weight management, and education about risk factor management. It is estimated that more than 50% of metabolic syndrome patients can be successfully treated by intensified modifications of lifestyle and behavior alone.10 Therefore, lifestyle and habitual behavior modifications are essential and effective components of the treatment of metabolic syndrome. Regular exercise represents a significant behavioral modification, because continued and regular exercise can reduce CVD risk and promote cardiovascular health. However, despite the benefits of regular exercise behavior, more than half of those who begin an exercise program stop it within 3 to 6 months.13,14 Strategies that seek to increase participation in a regular exercise regimen and sustain this participation in people with metabolic syndrome have been hindered by the lack of knowledge concerning the psychobehavioral strategies based on the readiness of individuals to engage in exercise behavior.
Exercise Behavior and the Transtheoretical Model
Exercise is important in reducing the cardiovascular risk in people with metabolic syndrome.3,7,15 Although health care providers emphasize exercise and lifestyle changes for adults with metabolic syndrome, most of these people are unlikely to follow the recommendation for regular exercise behavior.3 A truly effective strategy is needed to encourage adoption and maintenance of an exercise regimen. The majority of previous studies in adults with metabolic syndrome have focused mainly on the prevalence and characteristics of metabolic syndrome risk factors and their exercise status.4,6,8,16 Comparatively little is known regarding psychobehavioral strategies of Korean adults with metabolic syndrome who regularly exercise.
The transtheoretical model (TTM) provides a framework to assist individuals to make transitions across the various stages of exercise behavior, which is recommended to achieve behavior changes.17 One unique strength of the TTM in terms of exercise research is that it focuses on the dynamic nature of moving from early (precontemplation) to the last stage (maintenance) of exercise. The model explains how, rather than why, behavioral changes occur.18 The main constructs of TTM include motivational readiness for stage of change, self-efficacy, decisional balance, and a number of experiential or cognitive and behavioral processes of change.17
The TTM has previously been applied to a variety of health behaviors including exercise behavior in healthy populations19-23 and people with chronic diseases.15,24-26 In particular, many researchers have commonly used this model to understand exercise behavior or physical activity by multiple tests of the model,21,25,26 to develop effective programs based on the TTM,27 and to evaluate the programs in clinical trials for the initiation of exercise behavior.24,25,28 The degree to which individuals endorse these constructs vary systematically with current participation in exercise behavior.19,22,29 However, the TTM has not been evaluated with respect to metabolic syndrome. Also, little is known about the associations of the TTM constructs with the stages of change for exercise behavior.
Therefore, this study was performed to identify the psychobehavioral strategies across the stages of changes and to determine the predictors of regular exercise behavior in people with metabolic syndrome. The ultimate goal of the study was to provide a foundation for lifestyle change programs developed based on these strategies, with the overall aim of reducing CVD risk in Korean adults with metabolic syndrome.
The purpose of this study was to test TTM-related variables and determine the predictors of regular exercise behavior in Korean adults with metabolic syndrome. The specific aims were (a) to describe the stages of change for exercise behavior and TTM-related variables; (b) to examine the processes of change, decisional balance, and self-efficacy across the stages of change; and (c) to determine a logistic model explaining regular exercise behavior in Korean adults with metabolic syndrome.
Design and Sample
This descriptive, cross-sectional survey design enrolled a convenience sample of 210 of a possible 240 (87.5%) eligible participants with metabolic syndrome at a university hospital in South Korea. Metabolic syndrome, according to NCEP-ATP III criteria,1 was defined if 3 or more of the following criteria were satisfied: abdominal obesity based on Korean Society for the Study of Obesity specific to the Korean population is waist circumference 90 cm or greater in men and 85 cm or greater in women,30 triglyceride level 150 mg/dL or greater, HDL-C level less than 40 mg/dL for men and less than 50 mg/dL for women, systolic blood pressure 130 mm Hg or greater or diastolic pressure 85 mm Hg or greater, and fasting plasma glucose concentration 110 mg/dL or greater. Participants who had normal blood analyses values or blood pressure values but reported taking antihypertensive or antidiabetic medication (insulin or oral agents) were classified as having hypertension or diabetes, respectively. Physicians were asked to review the medical records and conditions of all participants and then to refer eligible participants who met the inclusion criteria of the study. A total minimum sample size of 135 was required at an effect size of 0.30, a significance of .05, and a power of 80% using 2-sided tests and power analysis for a multivariate analysis of variance.31 This calculation was based on the effect size derived from a review of previous studies.20,26
Approval was obtained from the institutional review board at the authors' institution (AJIRB-CRO-06-131). Each participant accepted the explanation of the purpose of the study and voluntarily signed an informed consent form.
Participants were asked to complete a questionnaire that addressed demographics and TTM-related questions. The survey took 25 minutes to complete. Each participant received a booklet and a measuring tape as an incentive when the questionnaire was returned. Triglyceride, HDL-C, and fasting plasma glucose were collected by blood analysis, and blood pressure and waist circumference were manually measured by a research nurse in the outpatient clinic.
All participants completed the demographic and TTM-related questionnaires including stages and processes of change, decisional balance, and self-efficacy questionnaires. Regular exercise behavior was defined as at least 20 minutes of continuous vigorous exercise 3 times per week or at least 30 minutes of continuous moderate physical activity performed at a moderate pace 5 times per week.32,33
Stages of Change
The stages of change were assessed using a short-form ordinal scale of the stage of readiness for exercise behavior.24,34 This scale requires participants to choose which of 5 statements best describes his/her current regular exercise pattern and performance. Each of the statements corresponds to 1 of the 5 stages of change from contemplation to maintenance, as follows: "I currently do not engage in physical exercise, and I am not thinking about starting" (precontemplation stage); "I currently do not engage in physical exercise, but I am thinking about starting" (contemplation stage); "I currently engage in some physical exercise but not regularly" (preparation stage); "I currently engage in regular physical exercise, but I only started within the last 6 months" (action stage); "I currently engage in regular physical exercise, and I have done so for longer than 6 months" (maintenance stage). Each stage was assigned a numeric value on a continuous 5-point scale. A κ index of reliability of 0.78 (n = 20) for stage of readiness for exercise as determined using the behavior short-form scale has been reported over a 2-week period.23
Processes of Change
A previously developed scale of the processes of change for exercise behavior35 that was adapted for the Korean population26 was used in this study. This scale consists of 30 items that represent 10 experiential and behavioral processes that may affect exercise habits, and each process has 3 items. Possible subtotal score of 3 items will be ranged from 5 to 15 for each 10 processes of change scale. The experiential or cognitive processes of change include consciousness raising (undertaking to find out more about exercise behavior), dramatic relief (caring about the consequences of inactivity or nonexercise), environmental reevaluation (understanding how inactivity affects the physical and social environments), self-reevaluation (seeing oneself as an active person), and social liberation (awareness and acceptance of social changes encouraging active lifestyles). The behavioral processes of change are counter conditioning (substituting alternatives for inactivity or nonexercise), helping relationships (seeking out social support to help adopt or maintain exercise), reinforcement management (using rewards to encourage or maintain exercise behavior changes), self-liberation (choosing and making commitment to change), and stimulus control (avoiding or controlling stimuli or other causes that support inactivity or nonexercise). These processes were rated using a 5-point Likert scale ranging from "never" (1) to "repeatedly" (5), where a higher score indicates that the process was more frequently used to change exercise behavior. The reliability of the processes of change for exercise behavior scale was found to have a Cronbach α coefficient of .86 in young adults,35 .93 in diabetic adults,26 and .92 in the present study.
A previously developed scale of decisional balance for exercise behavior36 that was modified for the Korean population26 was used in this study. This scale consists of 10 items that address the pros (positive aspects or benefits of adopting or maintaining exercise behavior) and cons (negative aspects, barriers or costs of adopting or maintaining exercise behavior) of regular exercise. These 10 items were measured using a 5-point Likert scale ranging from "not important" (1) to "extremely important" (5), where a higher score represents stronger positive or negative opinions. The reliability of the decisional balance for exercise behavior scale was reported to have a Cronbach α coefficient of .85 in adults,36 .87 in diabetic adults,26 and .80 in the present study.
A previously developed scale of self-efficacy for exercise behavior37 that was adapted for the Korean population26 was also used in this study. This scale consists of 6 items that address confidence to be active in a variety of situations as follows: negative affection, excuse making, must exercise alone, inconvenient to exercise, resistance from others, and bad weather. A 5-point Likert scale was used ranging from "not at all confident" (1) to "completely confident" (5), where a higher score indicates more confidence to change exercise behavior. In terms of the reliability of this scale, the Cronbach α coefficient s were .96 in adults,37 .96 in diabetic adults,26 and .86 in the present study.
Metabolic Syndrome Risk Factors
Fasting plasma glucose was measured using a Hitachi 747 automatic analyzer (Hitachi, Tokyo, Japan), and triglyceride and HDL-C levels were measured using an Olympus Au5200 (Olympus, Tokyo, Japan). Blood pressure was manually measured using an HM-1101 mercury sphygmomanometer (Hico, Tokyo, Japan), and waist circumference was also measured using a measuring tape (Tanita, Tokyo, Japan). The American Heart Association guidelines38 for blood pressure measurement was followed, and the detailed procedure was as follows: each participant was seated comfortably, with the back supported and the upper arm bared and the legs were not crossed. The arm was supported at heart level without talking during the measurement. Blood pressures were manually measured twice by the trained nurse with a 5-minute rest period, and then the average of those readings was used to represent the participant's blood pressure.
SPSS version 12.0 (SPSS Inc, Chicago, Illinois) was used for the data analyses. Descriptive statistics were used to analyze demographic characteristics, metabolic syndrome risk factors, and TTM-related variables. Analysis of variance was used to determine whether decisional balance and self-efficacy differed significantly across the stages of change. Multivariate analysis of variance (MANOVA) with post hoc Tukey test was used to test the group differences with regard to the processes of change. A multivariate logistic regression analysis was used to determine the most important predictors of regular exercise stages. The dependent variable of the logistic model was non-regular exercise stages (0) versus regular exercise stages (1). The stages of regular exercise include the action and maintenance stages, and the non-regular exercise stages were the precontemplation, contemplation, and preparation stages. Independent variables were significant variables that were chosen from a univariate test using MANOVA, Student t test, Fisher exact test, or χ2 test for each variable: 7 processes of changes, pros, cons, self-efficacy, elevated blood pressure, HDL-C level, and smoking were included. Age and sex were also included as covariates. Statistical significance was accepted for 2-sided P < .05.
Demographic Characteristics and Metabolic Syndrome Risk Factors
Demographic characteristics and metabolic syndrome risk factors of the 210 adults with metabolic syndrome are detailed in Table 1 and briefly summarized here. The mean (SD) age of adults was 53.3 (10.7) years, and two-thirds were male (67.1%) and had attained at least a high-school education (74.8%). All participants had a high prevalence (>62%) of metabolic syndrome factors, with the least prevalent being low HDL-C level (42.6%). Mean (SD) waist circumference was 92.95 (7.88) cm in men and 88.35 (6.47) cm in women. Mean (SD) systolic blood pressure, diastolic blood pressure, triglyceride level, and fasting plasma glucose level were 135.04 (13.64) mm Hg, 82.86 (11.58) mm Hg, 220.03 (141.36) mg/dL, and 125.77 (35.48) mg/dL, respectively.
Differences in TTM-Related Variables Across Stages of Change for Exercise Behavior
Differences in processes of change, decisional balance, and self-efficacy across the stages of change for exercise behavior are shown in Table 2. Participants with metabolic syndrome were allocated to 5 stages of change for exercise behavior: 9.0% in the precontemplation stage, 17.6% in the contemplation stage, 21.4% in the preparation stage, 13.3% in the action stage, and 38.6% in the maintenance stage. Self-reevaluation among experiential processes of change had the highest score (mean, 12.37 [SD, 2.63]), and reinforcement management had the highest score among the behavioral processes of change (mean, 12.64 [SD, 2.45]). Whereas all processes of change were least used during the precontemplation stage, most processes of change except consciousness raising, environmental reevaluation, helping relationship, and stimulus control were frequently used during the maintenance stage. Consciousness raising and stimulus control were most used during the action stage, and environmental reevaluation and helping relationship during the contemplation stage. The cons of exercise decreased, and pros and self-efficacy of exercise increased as adults progressed to the latter stages of change: pros (mean, 22.26 [SD, 3.59]) and self-efficacy (mean, 22.26 [SD, 5.10]) of exercise were the highest in the maintenance stage, but cons of exercise (mean, 7.32 [SD, 2.54]) was the lowest in this stage.
The MANOVA test was performed to test the group differences with regard to the processes of change. The analysis of the processes of change was significant (F = 4.443, P < .001). Significant differences in TTM-related variables across the stages of change for exercise behavior were shown in consciousness raising (P < .01), dramatic relief (P < .01), self-reevaluation (P < .001), social liberation (P < .01), counter conditioning (P < .001), self-liberation (P < .001), stimulus control (P < .001), pros of exercise (P < .05), cons of exercise (P < .001), and self-efficacy (P < .001). Post hoc analysis revealed that adults in the precontemplation stage used significantly less processes of change, whereas adults in the maintenance stage used them the most frequently (Table 2).
Predictors of Regular Exercise Behavior Based on the TTM
A multivariate logistic model was used to determine significant predictors of regular exercise behavior based on the TTM as shown in Table 3. We classified the stages of change into regular exercise stages versus non-regular exercise stages: regular exercise stages (n = 109) were the action and maintenance stages, whereas non-regular exercise stages (n = 101) included the precontemplation, contemplation, and preparation stages. Goodness of fit by the logistic regression analysis showed that the −2 log likelihood of regular exercise stages was 111.782, and model fit had a χ28 value of 10.489 (P = .232). The logistic regression model explained 73.8% of the variance in the regular exercise stages (Nagelkerke R2 = 0.738), and its percentage of correct prediction was 89.6% (χ215 = 155.353, P < .001). Adults in the regular exercise stages had higher HDL-C levels (odds ratio [OR] = 1.08, P < .05) than those in non-regular exercise stages. Similarly, consciousness raising (OR = 1.27, P < .05), self-reevaluation (OR = 1.48, P < .05), and self-liberation (OR = 2.310, P < .001) were more likely to be used, whereas pros by 1.48 times (OR = 0.676, P < .01) and cons by 1.38 times (OR = 0.726, P < .01) were less likely to be used in the regular exercise stages, compared with the non-regular exercise stages.
This is, to our knowledge, the first use of a TTM-based survey for Korean adults with metabolic syndrome in South Korea. More than two-thirds of the study participants presented with elevated blood pressure, triglycerides level, waist circumference, and plasma glucose level, and about 40% had a decreased HDL-C levels. The findings revealed much higher prevalence rates of metabolic syndrome risk factors than the ones of adults 30 years or older without metabolic syndrome as determined by the National Health and Nutrition Examination Survey.39 In a different sample of adults with metabolic syndrome from a rural community, most reported having risk factors, but increased fasting plasma glucose level was the most prevalent,4 unlike the present highest prevalence of elevated blood pressure in this sample. This difference may reflect variations in participant ages and locale.2-8
The Centers for Disease and Prevention and the American College of Sports Medicine guidelines state that at least 30 minutes of moderate-intensity exercise for 5 days a week or at least 20 minutes of continuous vigorous exercise for 3 days per week are required to keep and/or promote physiological and psychological benefits of exercise.32,33 More than half of the participants in this study engaged in the recommended amounts of regular exercise behavior for at least 1 month. This percentage is higher than that reported in adults without metabolic syndrome39 and in adults with type 2 diabetes.26 This result may indicate that adults with metabolic syndrome are more likely aware of the importance of regular exercise because they comparatively tend to have more illness conditions. Also, support received from various health care practitioners during their health care visits may provide encouragement for them to exercise regularly. Despite the high percentage of practicing regular exercise, it is predicted that almost half of the adults adopting exercise may discontinue the exercise within 6 months.13,14,19 In one study, the percentage of relapse or termination of exercise was 45.1% among young US adults.19 Hence, future longitudinal studies are needed to explore how to prevent people from terminating regular exercise and develop effective strategies to maintain their regular exercise behaviors. In addition, health care providers should continue to encourage regular exercise participation.
The findings from this study support the notion that the importance of TTM-related variables is different depending on the stages of exercise behavior. We found that most of the processes of change except environmental reevaluation, help relationship, and reinforcement management showed significant differences across the stages of change for exercise behavior. Whereas all strategies based on TTM-related variables were least used during the precontemplation stage, most strategies were most used during the maintenance stage. These findings are supported by previous studies that reported that processes of change are used least in the precontemplation stage.18,25,40 The significance of each TTM variable may be distinct in a different population.17 The significant TTM variables in this sample will provide useful strategies to help in the development of a tailored exercise program specific to the stages of change for Korean population. Of the processes of change, experiential processes were not consistent with the previous studies including different populations from this study. It has been reported that experiential processes of change were used most in the early stages, whereas behavioral processes of change were more frequently used during the later stages.17,18 In contrast, post hoc testing in the present study revealed that all the experiential processes of change except environmental reevaluation were significantly higher in the later stages than in the early stages. We found that the cons of exercise decreased, and the pros and self-efficacy of exercise increased as adults progressed into the latter stages. The differences between pros, cons, and self-efficacy across the stages of exercise were statistically significant. Self-efficacy scores in this study were lower in the precontemplation stage than in the other stages. These results are consistent with those of previous studies.17,19,24 The pros increased from precontemplation to maintenance stages; however, the cons decreased significantly from contemplation and preparation stages to the maintenance stage. These result are similar to those in other studies.26,36
With regard to the associations among the TTM-related variables and regular exercise behavior, the adults in regular exercise stages were likely to have higher consciousness raising, self-reevaluation, and self-liberation, compared with those in non-regular exercise stages. This finding is consistent with the previous report that consciousness raising, self-reevaluation, and self-liberation have moderate effects in the latter stages of change.41 The results suggest that future intervention programs for regular exercise behavior stages could consider including the strategies to increase choosing and/or making commitment to regular exercise (self liberation), increasing knowledge or undertaking to find out more about exercise behavior (consciousness raising), and comprehending the benefits of being physically active (self-reevaluation). Decisional balance reflects the weighing of the pros and the cons of engaging in exercise behavior.17 The pros and cons of exercise were statistically significant factors to predict the regular exercise stages. But, unlike other TTM-related variables, the adults in non-regular exercise stages were more likely to use them than those in regular exercise stages. The pros and cons are essential, particularly for individuals in earlier stages of change, but not in the latter stages.25,40,42 The results may suggest that the adults in regular exercise stages had already perceived the benefits and costs of regular exercise, so that they were less likely to use both pros and cons, compared with those in non-regular exercise stages.
High-density lipoprotein cholesterol level was also associated with regular exercise behavior in the present study. The adults in regular exercise stages were more likely to have higher HDL-C levels than those in non-regular exercise stages in this study. This result supports the suggestion that an elevated HDL-C level is associated with a reduced risk of CVD, which is in part due to the role that HDL-C plays in reverse cholesterol transport.43 Presently, mean HDL-C level was higher in women (51.25 mg/dL) than men (44.85 mg/dL). Estrogen tends to decrease CVD risk in women44; hence, the HDL-C levels of premenopausal women are higher than those of men.11 But, CVD risk is increased in postmenopausal women and is associated with the decrease in the HDL-C level that is both substantial and exceeds the decrease in men of similar age.4 Therefore, future research should consider to develop specific programs for postmenopausal women to decrease CVD risk in older women.
In this study of regular exercise behavior and TTM-related variables, consciousness raising, self-reevaluation, and self-liberation were associated with a positive effect on regular exercise behavior in adults with metabolic syndrome. Our findings could be used to develop strategies and interventions for regular exercise behavior directed at Korean adults with metabolic syndrome aimed at reducing the risk of CVD. Further prospective intervention studies are needed to investigate the effect of regular exercise program on the prevention and/or reduction of CVD risk among this population. Longitudinal prospective research is needed to determine the ability of TTM to predict forward stage transitions, in particular regular exercise behavior stages. Health care providers, especially nurses, are optimally positioned to help their clients initiate and maintain regular exercise behavior in clinical and community settings.
The authors thank Drs Dae-Jung Kim and Jae-Beom Park for their help with data collection and the study participants.
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