Long-term Effects Of Exercise-based Rehabilitation In The Control Of Traditional Cardiovascular Risk Factors In Elderly Individuals With Stable Coronary Artery Disease

Backgrounds and ObjectiveCardiovascular disease(CVD), headed by coronary heart disease(CHD), remains the leading cause of death worldwide with the rapid socio-economic development and the consequent improvement in living conditions, population aging process to speed up, especially in China. According to the report on CVD in China(2014), the prevalence of CVD was more than twenty percent and CVD mortality accounted for more than forty percent of all deaths. CVD morbidity and mortality continue to rise and remain on a high level which can be mainly attributed to the rising ischemic heart disease(IHD) morbidity and mortality, and the incidence of CHD had reached 0.77 percent while the mortality was close to 0.1 percent by 2013. With the advent of the era of evidence-based medicine(EBM) and rapid development of percutaneous coronary intervention(PCI) treatment, treatment outcome of patients with CHD has been greatly improved and the risk of disability and premature death induced by CHD has also decreased significantly. However, they do little to the potential causes which will speed up the initiation and progression of CHD. That’s the key reason why CHD morbidity and mortality continue to rise in our country.We identified hypertension, dyslipidemia/abnormal glucose tolerance, diabetes, smoking, abdominal obesity, lack of physical activity, aging and so forth as traditional cardiovascular risk factors for CHD based on the Framingham Heart Study. One hand, it’s reported that there are up to 80%-90%CHD patients being with at least one of them. On the other hand, registered researches from the developed countries like Turkey, the Czech republic and Portugal show that CHD mortality has declined by 21%～66% since the end of the 20th century, while effective control measures aiming at the traditional risk factors are responsible for 42%～52% of the reduced CHD deaths.As a key component of the secondary prevention of CVD, cardiac rehabilitation(CR) has been defined as "the provision of comprehensive long-term services involving medical evaluation, prescriptive exercise, cardiac risk factor modification, and education, counseling and behavioral interventions, aiming at weakening the adverse physical and psychological effects of heart diseases, reducing the risk of recurrence of myocardial infarction and sudden death, controlling cardiac symptoms, stabilizing or reversing the process of atherosclerosis(AS) and improving the psychological and professional status of patients with heart diseases". Specifically, CR for CHD includes patient assessment, nutrition counseling, weight management, blood pressure management, lipid management, diabetes management, psychosocial management, tobacco cessation, physical activity management and exercise training(ET), while ET is the key part and it’s the active patient participation in disease treatment with purposeful, planned, regular exercise programs on the basis of routine therapy.Numerous evidences of EBM have shown that exercise-based CR can reduce the mortality of patients with CHD significantly since the 1980s. O’Connor’s meta-analysis including 22 randomized controlled trials(RCTs) which evaluate the effects of exercise rehabilitation on patients with myocardial infarction(MI) shows that exercise rehabilitation can reduce all-cause mortality by 4%-34%, cardiovascular mortality by 4%～37% and incidence of fatal MI by 5%～41% in patients with MI. Similarly, Karam’s meta-analysis shows that CR can lower the risk of all-cause death by 13%～26%, cardiovascular mortality by 20%～36% and the risk of recurrence of myocardial infarction by 25%-47%. In addition to the improvement in cardiovascular risk factors like lipids, blood pressure, blood sugar, obesity and smoking due to the management aiming for them in CR programs, ET particularly has following anti-atherosclerosis effects:(1) ET improves endothelial function by increasing the shear stress acting on arterial wall and mediated by blood flow, also increases the synthesis and release of nitric oxide who will cause artery vasodilatation and prevent the progress of AS and thrombosis. (2) ET and the consequent improvement in cardiopulmonary fitness can lower the level of C-reactive protein significantly, which shows that ET has anti-inflammatory effect thus can stabilize the coronary artery plague. (3) ET or regular physical activity can lower weight and blood pressure, improve blood lipids including decreasing the level of serum total cholesterol(TC), low-density lipoprotein cholesterol(LDL-C), triglyceride(TG) and increasing the level of high-density lipoprotein cholesterol(HDL-C), improve insulin resistance and keep the steady state of blood sugar. (4) Endurance training raises myocardial ischemic threshold via improving compliance or elasticity of coronary artery and promoting collateral circulation formation of ischemic myocardial, and so forth.As stated earlier, CHD is the main cause resulting in residents disability and death worldwide, of which more than half of the patients with acute myocardial infarction and as much as 80% of deaths due to CHD are elderly individuals. The evidence-based medicine and interventional therapy have reduced the mortality in acute CHD significantly and CR will further decrease the mortality by 21%～34% on that basis. In addition, there are studies to show that either exercise therapy or comprehensive CR programs can effectively improve the cardiovascular risk factors and quality of life in patients with CHD. However, most of them are mainly about short-term(3 months or less) effects of ET/CR in patients with CHD and focused on middle-aged individuals. There are few studies discussing the long-term effects of exercise rehabilitation on cardiovascular risk factors in elderly patients over 60 years of age with CHD, our research will further investigate the above issues.Methods1. Study populationChoose the elderly patients with stable coronary heart disease(SCHD) aged from 60 to 75 who went to see a doctor in our hospital from March 2014 to July 2014 and a total of 70 subjects were enrolled in the study including 43 males and 27 females. The median age of them is 65(61.0,70.3). Subjects were randomly divided into two groups:the control group(35 cases) and the exercise rehabilitation group(35 cases).2. Intervention methodsWe conducted a preliminary assessment, health education on CHD and standardized the secondary prevention medicine for all enrolled individuals.The patients in control group were treated according to above conventional treatments. We evaluated the myocardial ischemic threshold and exercise capacity of patients in exercise rehabilitation group via symptom-limited exercise testing and directed them to conduct an exercise rehabilitation on the basis of conventional treatments. Exercise prescription as follows:(1)mode of exercise:walking or jogging with the help of exercise treadmill; (2)exercise intensity:50%～80% of the maximum intensity [target heart rate=50%～80%* (maximum heart rate-resting heart rate)+resting heart rate] or self-perceived exertion level indicated by Borg score arrives 12-16 points. Start from low intensity and increase gradually; (3) exercise duration:a total of 30～60 minutes including 5-10 min warm-up and 5-10 min relaxation time respectively. Patients in exercise rehabilitation group selected one or more kinds of aerobic exercise ways like walking, jogging, biking, walking or jogging with the help of exercise treadmill, swimming, playing badminton and so forth after discharge, the exercise intensity and duration didn’t change, the exercise frequency was 3-5 times per week. The patients came to hospital once every two weeks and conducted an exercise rehabilitation under the guidance of physicians following the above exercise prescription. It switched to be family rehabilitation under the supervision of physicians via telephone or clinic visit after 3 months. It must be emphasized that patients in exercise rehabilitation group should be come to our hospital for exercise treadmill testing every 3 months in order to evaluate their exercise endurance and the effects of exercise rehabilitation, thus we further adjusted the exercise prescription according to the results.The follow-up time was one year. Patients in both groups should come to our hospital every three months for electrocardiographic(ECG) examination, cardiac ultrasonography, chemical examination of related biochemical indicators. Thus we assessed the cardiovascular risk factors indicated by body mass index (BMI), waist circumference(WC), systolic blood pressure(SBP), diastolic blood pressure(DBP), blood lipids as TC, TG, LDL-C, HDL-C, HbAlc and smoking status for all subjects. We also evaluated their exercise capacity indicated by 6-minute walking distance(6-MWD) and adjusted drug therapy for all of them according to above results of inspection.3. Statistical analysisAll statistical analyses were performed with SPSS 20.0 software. Measurement data were tested for normality first. Descriptive characteristics were expressed as mean±standard deviation and comparisons between two groups were achieved via independent-samples t test while comparisons between before and after intervention in one group were achieved via paired-samples t test if measurement data were consistent with normal distribution. On the other hand, descriptive characteristics were expressed as median(Q1, Q3) and comparisons between two groups were achieved via nonparametric test(Mann-Whiteney U test) while comparisons between before and after intervention in one group were achieved via wilcoxon signed rank test if measurement data were inconsistent with normal distribution. The enumeration data were expressed as percentage or rate and comparisons between before and after intervention in one group were achieved via McNemar test while comparisons between two groups were achieved via chi-square test or Fisher’s exact probability test, P< 0.05 was considered as statistically significant.Results1. Comparison of general information between two groupsAt the end of follow-up, there were 6 cases lost to follow-up in the exercise rehabilitation group and 3 cases in control group. Finally, exercise rehabilitation group remained 17 males and 12 females with an average age of 64.0(60.0,68.5); control group remained 21 males and 11 females with an average age of 64.5(61.0, 71.5). There were no significant difference in general information between two groups(P> 0.05). The prevalence of dyslipidemia, hypertension, overweight, diabetes and smoking of the whole subjects were 83.6%,72.1%,55.7%,39.3% and 29.5% respectively.2. Comparison of BMI, WC before and after intervention between two groupsCompared with before intervention, BMI decreased by (0.90±0.80)kg/m2 at 3 months, (1.01±0.86)kg/m2 at 6 months, (0.73±1.10)kg/m2 at 9 months and (0.85±1.27)kg/m2 at 12 months respectively in the exercise rehabilitation group, and the differences were all statistically significant(P< 0.01); WC reduced by (2.4±3.3)cm at 3 months, (1.8±3.5)cm at 6 months, (1.9±3.2)cm at 9 months and (1.7±2.8)cm at 12 months respectively in the exercise rehabilitation group, and the differences were all statistically significant(P< 0.05). Changes in the control group showed no statistical difference(P> 0.05).There were no significant difference of overweight rates when compared between two groups or before and after intervention in one group(P> 0.05).3. Comparison of blood pressure before and after intervention between two groupsCompared with baseline, SBP decreased by (7.06±13.03)mm Hg at 3 months, (5.17±6.90)mm Hg at 6 months, (4.48±7.89)mm Hg at 9 months and (4.22±10.89)mm Hg at 12 months respectively in the exercise rehabilitation group, and the differences were all statistically significant(P< 0.05), while changes in DBP showed no statistical difference(.P> 0.05). Changes in the control group showed no statistical difference(P>0.05).Compared with baseline, hypertension rate decreased by 20.7% at 6 months in the exercise rehabilitation group, and the difference was statistically significant(P=0.031). Except for that, there were no significant difference of hypertension rates in comparison between two groups or before and after intervention in one group(P>0.05).4. Comparison of blood lipids before and after intervention between two groupsCompared with baseline, TC decreased by (0.42±1.10)mmol/L at 3 months and (0.46±0.98)mmol/L at 6 months in the exercise rehabilitation group, the differences were all statistically significant(P< 0.05); TG decreased by (0.38±0.64)mmol/L at 3 months and (0.33±0.85) mmol/L at 12 months in the exercise rehabilitation group, the differences were all statistically significant(P< 0.05); LDL-C decreased by (0.34±0.85)mmol/L at 3 months and (0.35±0.90)mmol/L at 6 months in the exercise rehabilitation group, the differences were all statistically significant(P< 0.05); HDL-C increased by (0.17±0.23)mmol/L at 3 months, (0.22±0.28)mmol/L at 6 months,(0.13±0.23)mmol/L at 9 months and(0.11±0.20)mmol/L at 12 months in the exercise rehabilitation group, the differences were all statistically significant(P< 0.01). Changes in the control group showed no statistical difference(P> 0.05).Compared with baseline, the prevalence of dyslipidemia decreased by 27.6% at 6 months,34.5% at 9 months and 27.6% at 12months in the exercise rehabilitation group, while the prevalence of dyslipidemia decreased by 28.1% at 9 months in the control group, the differences were all statistically significant(P< 0.05); Except for that, there were no significant difference of prevalence of dyslipidemia in comparison between two groups or before and after intervention in one group(P> 0.05).5. Comparison of HbAlc in diabetic patients before and after intervention between two groupsCompared with baseline, HbA1c of diabetic patients decreased by (1.57±0.92)% at 3 months, (1.59±0.93)% at 6 months, (1.40±1.00)% at 9 months and (1.28±1.07)% at 12 months in exercise rehabilitation group, the differences were all statistically significant(P< 0.01). Changes in the control group showed no statistical difference(P > 0.05).There were no significant difference of HbA1c compliance rates in diabetic patients when compared between two groups or before and after intervention in one groupCP> 0.05).6. Comparison of smoking prevalence before and after intervention between two groupsCompared with baseline, smoking prevalence decreased by 20.69% at 3 months, 20.69% at 6 months,24.14% at 9 months and 20.69% at 12 months in the exercise rehabilitation group, smoking prevalence decreased by 18.75% at 3 months in the control group, the differences were all statistically significant(P< 0.05). Except for that, there were no significant difference of smoking prevalence in comparison between two groups or before and after intervention in one group(P 0.05).7. Comparison of 6-minute walk distance(6MWD) before and after intervention between two groupsCompared with baseline,6MWD increased by (62.7±27.6)m at 3 months, (79.5±28.3)m at 6 months, (91.0±29.4)m at 9 months and (97.1±32.4)m at 12 months respectively in the exercise rehabilitation group, the differences were all statistically significant(P< 0.01). Changes in the control group showed no statistical difference(P >0.05).Conclusions1. Dyslipidemia is the most common risk factor in elderly individuals with stable CHD, and other risk factors like hypertension, diabetes, overweight and smoking are also at a high level in them.2. Long-term(one year) exercise rehabilitation can sustainably lower BMI, WC, SBP, HbAlc and smoking prevalence, also increase HDL-C. Thus we can infer that exercise rehabilitation can sustainably improve the degree of obesity, blood pressure, blood lipids, bood sugar and smoking status in elderly patients with stable CHD.3. Exercise rehabilitation can significantly increase the exercise endurance in elderly patients with stable CHD, and their exercise endurance will keep ascending with exercise time going.