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

  1. Can physical activity reduce the risk of CVD?

  2. Is moderate-intensity activity sufficient?

  3. Can bouts of activity be accumulated?

  4. 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).