Who is more susceptible to hyperthermia?

September 24, 2025 •

4 min read

Heat-related illness, which includes hyperthermia, is a leading cause of weather-related death in the United States. Understanding who is more susceptible to hyperthermia is the critical first step toward proactive prevention, ensuring safety for yourself and those you care for during high temperatures.

Quick Summary

Infants, older adults, pregnant people, athletes, and outdoor workers are at heightened risk due to physiological limitations and environmental exposure. Individuals with chronic illnesses, obesity, or those taking certain medications also have an increased vulnerability to overheating.

Key Points

Age is a major factor: Both infants and young children, as well as older adults (65+), have less efficient thermoregulation and are highly susceptible to overheating.
Chronic conditions increase risk: Underlying health issues like heart disease, diabetes, and respiratory problems can worsen with heat stress, making sufferers more vulnerable.
Medications can interfere: Certain common prescription drugs can disrupt the body's natural cooling mechanisms and reduce its ability to sweat.
Lifestyle and exertion matter: Outdoor workers, athletes, and obese individuals are at a higher risk due to increased metabolic heat or prolonged exposure.
Prevention is key: Staying hydrated, seeking air-conditioned environments, and wearing appropriate clothing are simple but effective measures to protect vulnerable individuals.

Understanding Your Body's Thermoregulation

Your body has a natural and efficient cooling system, primarily involving sweating and increased blood flow to the skin, which releases heat. Hyperthermia occurs when this system is overwhelmed and cannot dissipate heat effectively, leading to a dangerously high core body temperature. While anyone can be affected, several factors can compromise this cooling process, placing specific populations at a much higher risk.

Age-Related Vulnerabilities

Age plays a significant role in determining hyperthermia susceptibility. Both the very young and the elderly have less efficient thermoregulatory systems.

Infants and Young Children

Infants are particularly sensitive to extreme heat due to their undeveloped thermoregulatory systems. Key factors include:

Higher body surface area to mass ratio: This means they absorb heat more easily from their surroundings.
Less efficient sweating: Their sweat glands are not fully developed, hindering their ability to cool themselves effectively through evaporation.
Dependence on caregivers: Infants cannot independently remove themselves from hot environments, regulate their clothing, or hydrate themselves. A prime example of this risk is leaving children unattended in a car, where temperatures rise rapidly to dangerous levels.

Older Adults (65+)

As we age, our bodies become less capable of responding to sudden temperature changes, making older adults highly susceptible.

Diminished physiological responses: The central nervous system's ability to regulate temperature declines, and skin blood flow may be reduced.
Chronic medical conditions: Pre-existing conditions are more common in older adults and can be exacerbated by heat.
Medication use: Many prescription medications affect the body's ability to sweat or control temperature.

Health and Lifestyle Factors

Beyond age, a person's health status and daily habits can significantly increase their risk.

Individuals with Chronic Medical Conditions

Chronic illnesses often compromise the body's ability to manage heat stress effectively.

Cardiovascular disease: Heart and blood vessel conditions can impair the heart's ability to pump blood efficiently to the skin for cooling.
Diabetes: People with diabetes are at higher risk for dehydration and can have impaired sweating function.
Mental illness: Certain psychiatric conditions and their medications can interfere with temperature regulation.
Other conditions: Kidney disease, respiratory illness, and skin conditions like anhidrosis (inability to sweat) also increase risk.

Overweight and Obese Individuals

Excess body fat acts as an insulator, trapping more heat within the body. This, combined with an increased metabolic heat production for the same activity level, places obese individuals at greater risk.

Outdoor Workers and Athletes

Anyone engaged in strenuous physical activity in hot, humid conditions is at risk for exertional hyperthermia.

High metabolic heat: Intense exercise dramatically increases the body's internal heat production.
Environmental exposure: Those working outdoors in jobs like construction or firefighting are directly exposed to high temperatures for long periods.

People on Certain Medications

Some medications can disrupt the body's natural cooling mechanisms, making heat exposure more dangerous. This includes:

Diuretics
Beta-blockers
Antidepressants
Anticholinergics
Stimulants

A Comparison of Vulnerable Populations


Vulnerable Group	Why They Are at High Risk	Key Protective Measures
Infants & Young Children	Undeveloped thermoregulation, dependent on others for hydration and shade.	Never leave unattended in cars. Ensure proper hydration and loose, light clothing. Monitor for signs of overheating.
Older Adults (65+)	Reduced ability to sense/respond to heat, pre-existing conditions, medication side effects.	Ensure access to air conditioning. Stay hydrated. Check on elderly neighbors. Review medications with a doctor.
Pregnant People	Increased body temperature and metabolic rate, higher dehydration risk.	Avoid strenuous activity in the heat. Stay hydrated. Seek shade and cool environments.
Outdoor Workers/Athletes	High heat production, prolonged exposure, potential dehydration.	Take frequent breaks in the shade. Stay well-hydrated. Acclimatize gradually to hot weather.
Obese Individuals	Body fat acts as insulation, higher metabolic heat production.	Stay hydrated. Seek cool environments. Avoid strenuous activity during peak heat.
Chronic Illness Sufferers	Conditions like heart disease or diabetes worsen with heat stress.	Follow medical advice. Stay in air-conditioned areas. Be aware of medication effects. Monitor symptoms closely.

Strategies for Mitigating Risk

Regardless of your susceptibility level, proactive steps can help prevent hyperthermia and its complications.

Stay hydrated: Drink plenty of fluids, especially water, throughout the day. Avoid alcohol and caffeine, which can cause dehydration.
Seek cool environments: Spend time in air-conditioned spaces during the hottest parts of the day. Utilize public cooling centers, malls, or libraries if needed.
Dress appropriately: Wear lightweight, light-colored, and loose-fitting clothing.
Pace yourself: Schedule strenuous outdoor activities for cooler morning or evening hours. Take frequent breaks in the shade.
Check on others: During heat waves, make a special effort to check on elderly relatives, friends, and neighbors who may be vulnerable or isolated.

Conclusion

While hyperthermia can affect anyone exposed to sufficient heat stress, the risk is significantly elevated for specific groups due to a combination of physiological, health, and environmental factors. Recognizing these vulnerabilities and taking preventative action is essential for protecting the most susceptible members of our communities. Educating yourself and others is the first line of defense against heat-related illness.

For more information on heat-related illnesses and safety, refer to the resources provided by the CDC: Heat and Your Health.

Frequently Asked Questions

Infants have a larger body surface area relative to their body mass and their sweat glands are not fully developed. This combination makes it harder for them to regulate their body temperature and cool themselves down effectively.

Older adults are at higher risk because their central nervous system is less able to detect and respond to temperature changes. They also often have chronic medical conditions and take medications that can interfere with the body's cooling processes.

Excess body fat acts as an insulator, trapping heat inside the body and making it more difficult to cool down. Additionally, obese individuals may generate more heat during physical activity compared to people with a lower body mass.

Yes, some medications, including certain diuretics, beta-blockers, and antidepressants, can affect the body's ability to regulate temperature or sweat, increasing the risk of heat-related illness.

Outdoor workers and athletes should take frequent, shaded breaks, stay well-hydrated by drinking plenty of water, and wear loose-fitting, light-colored clothing. They should also try to acclimatize gradually to hot environments.

Yes, pregnant individuals are more vulnerable to overheating. Their bodies have an increased temperature and metabolic rate, and they are more susceptible to dehydration, which can increase the risk of heat exhaustion and heatstroke.

Initial signs often include heavy sweating, muscle cramps, dizziness, headache, and nausea. Recognizing these early symptoms is crucial to prevent progression to more severe conditions like heat exhaustion or heat stroke.