The effects of heat waves on the human body, with particular emphasis on preventive measures that must be taken, especially by vulnerable groups of the population, were discussed by the Rector of the National and Kapodistrian University of Athens, Professor Gerasimos Siasos, on the main news bulletin of Alpha television station, presented by Maria Nikoltsou.
Read: Emergency weather bulletin from HNMS: Six-day heat wave coming – Temperatures to reach 43 degrees
Regarding the upcoming heat wave, Mr. Siasos explained which categories of citizens face increased risk and what are the basic protection measures they should follow for their safety.
The Rector emphasized that climate change has intensified the occurrence of extreme thermal phenomena, while noting that NKUA has already published detailed guidelines for prevention and protection of the population.
Urgent announcement from NKUA’s Risk and Crisis Management Committee regarding the approaching heat wave
In recent years, climate change has intensified extreme heat phenomena, with two characteristic manifestations standing out: prolonged heat waves with unusually high temperatures and the heat dome phenomenon, during which stable high pressures trap warm air in the lower atmosphere, creating a “dome” that prevents cooling and intensifies the heat.
These conditions not only increase environmental temperature to critical levels but also maintain thermal stress for days or even weeks, with significant consequences for public health globally. Continuous exposure to high temperatures causes multisystemic disorders, increasing morbidity and mortality, particularly among vulnerable populations.
Pathophysiology
When the human body is exposed to extreme thermal loads for extended periods, the physiological mechanisms maintaining balance (homeostasis) begin to malfunction or become insufficient. The basic disorders include:
Insufficient heat dissipation: When the body cannot effectively dissipate heat — due to reduced sweating or vasodilation — body temperature increases dangerously, leading to hyperthermia.
Electrolyte disorders: Dehydration from increased fluid loss disrupts concentrations of essential electrolytes such as sodium, potassium, and calcium. This imbalance directly affects heart and muscle function and overall neuromuscular function.
Oxidative stress and inflammatory response: Hyperthermia causes cellular damage, activation of inflammatory mechanisms, and release of pro-inflammatory cytokines (e.g., IL-6, TNF-α) with systemic inflammation.
Reduced blood flow to vital organs: Heat stress can cause arterial blood pressure drops, fluid retention, and microcirculatory disorders. This limits oxygen supply to sensitive organs like the brain, heart, and kidneys, leading to ischemic damage.
Clinical manifestations
Heat stress can manifest in various ways, depending on intensity, duration of exposure, and individual vulnerability. From mild discomfort to life-threatening conditions, clinical presentations include:
Heat exhaustion: This is an early and common manifestation, characterized by intense fatigue, dizziness, tachycardia, muscle cramps, and increased sweating. The person shows general weakness and often feels faint.
Heat stroke: The most severe form of heat stress. It constitutes an urgent medical emergency and manifests with high fever (usually above 40°C), neurological disorders such as confusion, lethargy, or seizures, while absence of sweating is characteristic. If not treated immediately, it can progress to multi-organ failure.
Worsening of chronic diseases: Cardiovascular events (such as acute myocardial infarction), respiratory crises (asthma, COPD), and kidney dysfunction worsen significantly under conditions of dehydration and electrolyte disorders.
Liver and neurological damage: In severe cases, hyperthermia can lead to liver tissue necrosis and severe brain dysfunction (encephalopathy), with loss of consciousness or even coma.
Vulnerable population groups
Certain population categories are particularly vulnerable to the effects of heat stress, either due to physiological limitations or pathological conditions that reduce the body’s ability to adapt to heat. Such population groups are:
Elderly: They face increased risk as they have reduced thermoregulation capacity, often suffer from chronic conditions, and may have limited fluid intake and reduced sense of thirst.
Infants and toddlers: Their body temperature regulation mechanisms have not yet fully developed, making them particularly vulnerable to high temperature conditions.
People with chronic diseases: Heart patients, kidney patients, patients with chronic respiratory or neurological problems are more likely to develop complications, as heat stress destabilizes their already fragile homeostasis.
People with psychiatric diseases: Besides difficulties in perceiving danger or self-care, many of the medications they take (such as antipsychotics) affect body thermoregulation.
Outdoor workers and athletes: Increased physical activity with increased metabolic heat production combined with sun exposure and high temperatures significantly increases thermal burden, resulting in higher risk of dehydration and heat exhaustion.
Prevention and management
Prevention of heat stress begins with early recognition of risks and adoption of practical measures that protect health, especially during periods of high thermal load. Early intervention saves lives and significantly reduces complications.
Adequate hydration: Systematic fluid intake — even without feeling thirsty — is a basic preventive measure. It’s good to avoid alcoholic and caffeinated drinks, which have diuretic effects and intensify dehydration.
Adaptation of environmental conditions: Staying in shaded or air-conditioned areas, avoiding activities during the hottest hours of the day, and wearing cool, light-colored clothing contribute substantially to relieving the body from heat.
Medical monitoring: Vulnerable groups should be monitored systematically, especially during heat wave days. Immediate recognition of symptoms like fatigue, dizziness, or confusion allows early intervention before the situation worsens and symptoms of heat exhaustion or heat stroke appear.
Heat stroke management: Heat stroke is an emergency requiring immediate action. Priority is rapid reduction of body temperature through physical cooling methods (cold compresses, immersion in cool water, use of fans). Simultaneously, hydration with isotonic fluids and correction of electrolyte disorders is essential. If necessary, vital function support is applied in a hospital setting.
Conclusion
The increasing frequency and duration of heat waves, as well as heat dome phenomena, now constitute a critical public health issue. Deeper understanding of the pathophysiology and clinical presentation of heat stress is essential, not only for early diagnosis and management of cases, but also for preventing serious complications in vulnerable populations.
Taking preventive measures and early medical intervention are fundamental pillars in reducing the consequences of these phenomena.
The Medical School of the National and Kapodistrian University of Athens appeals to all health professionals, state agencies, and broader society to strengthen information, education, and intersectoral cooperation. Only through coordinated and holistic actions can we ensure public health protection against a reality that is evolving with increasing intensity.
