Understanding Heatwaves: Body Effects and Who Faces the Greatest Risk

Exposure to extreme heat forces the body to widen peripheral blood vessels and sweat, which can lower blood pressure and increase cardiac workload, sometimes resulting in mild issues such as heat rash or swollen feet. Fluid and electrolyte loss from sweating may progress to heat exhaustion, marked by dizziness, nausea, fainting, confusion, muscle cramps, headaches, heavy sweating, and fatigue. The UK Health Security Agency recommends protecting at-risk groups—older adults, young children, people with chronic conditions, and those living alone—by staying indoors with curtains closed, drinking plenty of fluids, avoiding alcohol, limiting sun exposure between 11:00 and 15:00, using shade and high-SPF sunscreen, and wearing protective hats.

Medications like diuretics, antihypertensives, and some drugs for epilepsy, Parkinson’s, lithium or statins can worsen dehydration or impede cooling. If heat exhaustion does not improve within 30 minutes, it may develop into heatstroke, characterized by a core temperature above 40 °C, possible seizures, loss of consciousness and absent sweating, requiring immediate emergency assistance. Data from recent summers show thousands of excess deaths linked to heat, primarily from heart attacks and strokes triggered by the body's struggle to maintain a stable core temperature.