Physical Activity and Cardiovascular Disease (CVD)
Lecture Overview
Topic: Physical activity and cardiovascular disease (CVD)
Course: KHPM324 Chronic Diseases of Modern Society
Instructor: Hannah Oh, MPH, ScD
Division of Health Policy & Management, College of Health Sciences, Korea University
Announcements
Next Lecture (09/24): Start of Part 2 on Diabetes.
Reading Assignments:
Assignment #1 due on 09/28 by midnight (Sunday).
Guiding questions available on course website.
Submit answers online; discussions will be held on 09/29.
Assignment #2 due on 10/14 by midnight (Wednesday).
Class Schedule:
No class on 10/6 and 10/8 (National Holiday).
Recorded lecture video (Part I CVD review) will be posted.
Attendance (view history) will be recorded.
Deadline for submissions: 10/17.
Key Questions Addressed
Can physical activity reduce the risk of CVD?
Is moderate-intensity activity sufficient?
Can bouts of activity be accumulated?
How much total activity (hours/week) is needed to reduce the risk of CVD?
Mechanisms of Decreasing CVD Risk through Physical Activity
Plausible mechanisms include:
Anti-atherogenic effect:
Results in improved blood pressure and favorable lipid profile
Lipid Variables:
Increased HDL (high-density lipoprotein) levels, decreased LDL (low-density lipoprotein) levels.
Improved insulin sensitivity.
Reduction in body fat.
Decreased risk of thrombosis:
Promotes favorable changes in blood viscosity and inflammatory variables.
Decreased risk of myocardial ischemia:
Reduces myocardial oxygen demand.
Improves coronary blood flow and endothelial function.
Decreased risk of ventricular arrhythmia.
Blood Pressure Changes with Exercise
Blood Pressure Decrease:
Blood pressure changes (in mmHg) observed:
Systolic BP: -6.9 mmHg (Hypertension)
Diastolic BP: -4.9 mmHg (Prehypertension)
Source: Cornelissen et al., Hypertension 2005.
Effects on Lipids and Glucose Levels
Exercise and Change in Lipids, Glucose, and Insulin
Table 3:
Baseline Data for the Training Group and Weighted Net Changes in Response to Dynamic Aerobic Endurance Training:
Variables: Cholesterol, glucose, insulin, HOMA index.
Reported as weighted mean (95% confidence limits):
Total cholesterol: 5.5 (5.3; 5.8) mmol/L, n=688, Net Change (p-value: NS)
HDL: 1.4 (1.3; 1.4) mmol/L, n=923, Net Change (p-value: <0.05)
LDL: -0.040 (-0.13; 0.045), n=796, Net Change (p-value: NS)
Triglycerides: -0.11 (0.24; 0.0095) mmol/L, n=958, Net Change (p-value: 0.07)
Glucose: -0.15 (-0.20; -0.11) mmol/L, n=439, Net Change (p-value: <0.001)
Insulin: -1.4 (-2.2; -0.53) IU/L, n=376, Net Change (p-value: <0.005)
HOMA index: -0.31 (-0.53; -0.094) (p-value: <0.01)
Source: Cornelissen et al., Hypertension 2005.
Epidemiological Data on Physical Activity and CVD
Physical Activity and Coronary Heart Disease (CHD)
Observational studies:
Over 100 studies explored the relationship between physical activity and CHD prevention.
Active individuals exhibit a 20-30% lower CHD rate compared to inactive individuals.
Physically fit individuals show a 30-40% lower CHD rate.
Evidence suggests that the association is likely causal, despite the absence of RCTs focused on primary prevention.
Early Morris Studies
Historical Studies:
Conducted by Morris et al. (Lancet 1953) found that different occupations correlated with CHD rates.
Bus conductors, who were active, had significantly lower rates of CHD compared to bus drivers.
Included a one-year follow-up that revealed 30-50% lower rates of CHD in more active professions.
Data analysis:
Conductors climbed approx. 600 stairs/day which contributed to increased activity versus sedentary drivers.
Confounding Factors in Early Studies
Additional analysis revealed that drivers were often heavier with larger measurements, suggesting body fat confounded results, as drivers had higher waist sizes than conductors.
Morris et al. (Lancet 1956).
Current vs. Past Physical Activity
Physical Activity Questionnaire Analysis:
Prospective cohort study with 10-year follow-up:
Emphasized importance of current PA compared to PA during college years (16-50 years earlier).
Demonstrated genetic fitness alone does not sufficiently explain lower heart attack risk later in life.
Study by Paffenbarger et al. (AJE 1978) tracked Harvard alumni from 1962-1972.
Ex-varsity athletes retained lower risk of heart attack only if high PA levels were maintained post-college.
The Impact of PA Intensity on CHD
Moderate PA and CHD:
Nurses’ Health Study (Manson et al., NEJM 1999) showed:
Significant dose-response relationship with walking pace.
Average walking pace correlated with 25% lower CHD risk, brisk walking with 36% lower risk compared to those with easy/casual walking pace.
Prospective cohort study with 8 years of follow-up, accounting for various factors such as age and BMI.
Walking vs. Vigorous Exercise
Joint associations between walking and vigorous exercise indicate a similar risk reduction (approximately 30%) for CVD.
Recommendations and Guidelines for Physical Activity
Recommendations Pre and Post-1995
Pre-1995 Recommendation:
Engage in vigorous exercise at least 20 minutes continuously, 3 times per week (per American Heart Association).
Post-1995 Recommendation:
Introduced moderate physical activity.
Minimum bout of 10 minutes for any activity.
Dose-response concept included along with muscle-strengthening exercises.
Effect of Duration on PA
Lee et al., Circulation 2000 Study:
Five-year follow-up: Longer exercise sessions showed no significant differential risk impact as long as total energy expenditure remained constant.
Table of Relative Risks of Coronary Heart Disease
Derived from total energy expenditure in kJ/week, indicating decreased risk with increased physical activity.
Physical Activity Guidelines
Korean and US DHHS Guidelines for Adults
Korean Guidelines:
Reflect WHO guidelines:
Moderate-intensity aerobic activity: 150 min/week or vigorous-intensity: 75 min/week.
Muscle-strengthening activity on at least 2 days/week.
US DHHS Recommendations:
Emphasize participation in any amount of physical activity for health benefits.
150 min/week of moderate-intensity activity significantly reduces the risk of chronic diseases.
Differences in Guidelines' Focus
CDC, ACSM, AHA, DHHS:
Focus on health with a recommended 150 min/week.
Institute of Medicine (IOM):
Focus on weight control with a higher recommendation of 420 min/week.
Summary of Findings
Physiological Basis:
It is biologically plausible that physical activity can decrease CHD risk.
Epidemiological Evidence:
Active individuals show 20-40% lower CHD rates compared to inactive individuals.
Aim for 150 min/week of moderate-intensity physical activity, which can be accumulated in 10-15 minute bouts.
Greater total duration and/or intensity provides greater health benefits (dose-response).