Cardiac Physiology: Personality and Cardiovascular Disease

Risk Factors for Cardiovascular Disease (CVD)

• Heritability of CVD: 40-60% based on studies, including family, twin, and genome-wide association studies (GWAS).

• Lifestyle Factors: Influence overall cardiovascular health, though they are secondary to genetic predispositions.

Personality Types and CVD

• Historical Study (1959): Friedman and Rosenman's research categorized personality types related to cardiovascular findings, focusing on:

  • Type A Personality:

  • Competitive

  • Time Urgent

  • Hostile and Aggressive

  • Type B Personality:

  • Relaxed

  • Patient

  • Easy-going

• Limitations of Type A/B Framework:

  • Subsequent meta-analyses indicated that classifying personalities into just Type A or Type B is overly simplistic.

  • Emergence of Type D Personality (distressed) as common among patients with Coronary Heart Disease (CHD) (Denollet et al., 2010).

  • Studies using the Big 5 Personality Traits show a correlation between neurotic/nervous personality and increased risk of CHD (Dahlén et al., 2022).

Theories Linking Personality to CVD

• Personality-Induced Hyperactivity Model: Personality traits can lead to hyperactivity, contributing to cardiovascular strain.

• Dangerous Behavior Model: More aggressive and hostile personalities engage in risky behaviors that impact heart health.

• Transactional Stress Moderation Model: Personality traits can influence how one responds to stress, which affects cardiovascular health.

• Constitutional Predisposition Model: Some individuals may be genetically predisposed to certain personality types that can lead to CVD.

Autonomic Mechanisms of Personality Impacting CVD

• Aggression and Hostility: Activates the sympathetic nervous system, triggering:

  • Increased heart rate

  • Elevated blood pressure

  • Higher levels of adrenaline and cortisol

• Chronic Stress Exposure: Leads to atherosclerosis, plaque buildup, and increased risk of myocardial infarction (MI).

• Link Between Depression and CHD: Chronic emotional states can dysregulate the autonomic nervous system (ANS), with evidence showing increased noradrenaline levels in patients.

• Sympathetic vs. Parasympathetic Tone: Decreased parasympathetic and increased sympathetic tone can lower the threshold for serious cardiac events like ischemia, tachycardia, and cardiac death (Klicks et al., 1975).

Heart Rate Variability (HRV) and Its Implications

• Definition: HRV measures cardiac autonomic activity through beat-to-beat variations (R-R intervals).

• Balance in ANS: HRV reflects the balance between sympathetic and parasympathetic influences over heart rate.

  • Low HRV indicates heightened sympathetic activity or deficient parasympathetic modulation, both of which can predict mortality in patients with MI or CHD.

• Impact of Depression on HRV: Studies show that HRV is lower in depressed patients compared to non-depressed individuals, particularly in those with stable coronary disease or recent acute MI.

Contents:

1. Heritability of CVD

2. Lifestyle Factors

3. Personality Types and CVD

   • Historical Study (1959)

   • Type A Personality

   • Type B Personality

   • Limitations of Type A/B Framework

   • Emergence of Type D Personality

   • Studies using Big 5 Personality Traits

4. Theories Linking Personality to CVD

   • Personality-Induced Hyperactivity Model

   • Dangerous Behavior Model

   • Transactional Stress Moderation Model

   • Constitutional Predisposition Model

5. Autonomic Mechanisms of Personality Impacting CVD

   • Aggression and Hostility

   • Chronic Stress Exposure

   • Link Between Depression and CHD

   • Sympathetic vs. Parasympathetic Tone

6. Heart Rate Variability (HRV) and Its Implications

   • Definition

   • Balance in ANS

   • Impact of Depression on HRV