Understand Vulnerable Populations

Home » Population and Community Health » Planetary Health » Climate Change and Heat Impacts » Understand Vulnerable Populations
Headshot of Anne Grossman, MD, FACP · Assistant Professor, Medical Education and Clinical Sciences
Anne Grossman
MD, FACP · Assistant Professor, Medical Education and Clinical Sciences
envelope icon
Table of Contents

In a previous section

In the Extreme Weather Hazards module (Vulnerability and Preparedness), you were introduced to vulnerable populations affected by heat (elderly, chronically ill, infants, outdoor workers, and those without access to air conditioning). Now we’ll examine the specific physiologic and social mechanisms that create this vulnerability—knowledge you’ll need for clinical counseling and targeted prevention.

Physiologic mechanisms of vulnerability

Older Adults (≥65 years)
Mechanisms
  • Age-related decline in cardiovascular reserve limits the ability to increase cardiac output for heat dissipation.
  • Reduced sweat gland function impairs evaporative cooling.
  • Thirst perception decreases, leading to inadequate fluid intake.

Clinical note: Median age of PNW heat dome deaths was in the 70s.
Chronic Medical Conditions
  • Heart failure: Compromised cardiac output limits heat dissipation via increased skin blood flow.
  • Diabetes: Autonomic neuropathy may impair sweating; dehydration worsens glycemic control.
  • Chronic Kidney Disease: Reduced ability to concentrate urine; increased susceptibility to dehydration.
  • Psychiatric illness: Impaired self-care; may not recognize danger; medications often worsen heat tolerance.
Medication-Induced Vulnerability
Critical medications that increase heat vulnerability:
  • Diuretics: Cause volume depletion, reducing circulating blood available for heat dissipation.
  • Beta-blockers: Limit tachycardia needed to increase cardiac output for cooling.
  • Anticholinergics: Directly inhibit sweat production.
  • Antipsychotics: May impair heat perception and thermoregulation.
  • First generation antihistamines: Can reduce sweating capacity.

Clinical implication: Medication review is essential before heat season.
Infants and Young Children
Mechanisms
  • Higher surface area-to-mass ratio = faster heat gain from environment.
  • Immature thermoregulatory system.
  • Depend entirely on caregivers for cooling and hydration.

Clinical note: Cannot verbalize thirst or discomfort.
Pregnancy
Mechanisms
  • Increased metabolic rate generates more internal heat Cardiovascular system is already working harder; heat adds additional strain.

Clinical note: Heat exposure is linked to adverse pregnancy outcomes including preterm birth.

Social determinants that amplify physiologic risk

More vulnerable because:

  • Cannot afford air conditioning or reluctant to use due to electricity costs.
  • Live in older housing with poor insulation.
  • Work outdoor jobs without flexibility to modify schedule.
  • Less access to transportation to cooling centers.
  • Environmental justice mechanism:
    • Formerly redlined districts have 60–70% less tree canopy coverage.
    • More concrete and asphalt (high heat capacity).
    • Result: These neighborhoods are 5–12°F hotter than wealthier areas in the same city.
  • Compounding factors:
    • Lower air conditioning ownership.
    • Higher proportion of outdoor workers.
    • Language barriers to heat alerts and health information.
  • No escape from ambient heat; often have chronic medical conditions.
  • May have substance use disorders that impair judgment.
  • Socially isolated (no one to check on them); limited access to hydration and shade.
  • Generate metabolic heat through physical labor; often lack autonomy to take breaks.
  • May face productivity pressure from employers.
  • Language barriers or immigration status may prevent advocating for safety.

Key point

Heat vulnerability is not evenly distributed. Age, health status, medications, social factors, housing quality, occupation, and neighborhood characteristics all influence who suffers most. Identifying these high-risk individuals and intervening early can save lives.

Question

A 68-year-old patient with heart failure takes furosemide (diuretic) and metoprolol (beta-blocker). During a heat wave, which mechanism best explains their increased vulnerability to heat-related illness?

This answer demonstrates understanding of the mechanisms: Furosemide (diuretic) causes fluid loss, reducing the circulating blood volume available for heat dissipation through skin vasodilation. Metoprolol (beta-blocker) prevents the compensatory increase in heart rate and cardiac output needed to pump blood to the skin for cooling. Together, these medications create significant physiologic heat vulnerability.

Image credits

Unless otherwise noted, images are from Adobe Stock.

previous

Clinical Recognition and Management

Next

Protecting Health During Extreme Heat