Summer heat is having an increasingly noticeable impact on the health of people in Switzerland. During periods of high temperatures, doctors see a growing number of patients requiring urgent cardiac care.
According to Professor Frank Ruschitzka, Director of the Department of Cardiology at University Hospital Zurich, the department was almost completely full during the recent heatwave. The number of patients seeking medical attention for cardiovascular conditions increased significantly.
But why does heat affect the heart so strongly — and who is at increased risk?
When Heat Reveals Hidden Heart Problems
A person may be unaware for years that one of their coronary arteries has already become severely narrowed. At rest, the blood supply to the heart may still be sufficient, so no significant symptoms occur.
The situation can change during hot weather.
To prevent overheating, the body dilates blood vessels and directs more blood to the skin. The heart begins to beat faster and work harder. At the same time, sweating causes the body to lose fluids and electrolytes, the blood becomes more concentrated, and the strain on the cardiovascular system increases.
If the coronary arteries are already affected by atherosclerosis, the additional strain may cause the following symptoms to appear for the first time:
- pressure or burning pain in the chest;
- shortness of breath;
- unusual weakness;
- tingling or pain in the arm;
- dizziness;
- irregular heartbeat;
- a sudden increase or decrease in blood pressure.
Therefore, heat is not always the direct cause of a medical condition. It often acts as a trigger that causes a previously unnoticed problem to become apparent.
Why Several Consecutive Hot Days Are Particularly Dangerous
Cardiologists are most concerned not about a single hot day, but about prolonged heatwaves. The number of cardiovascular complications often begins to increase noticeably after the third or fourth day of high temperatures.
The body gradually exhausts its ability to adapt. The situation becomes particularly difficult when temperatures remain high at night and indoor spaces do not have enough time to cool down.
Under normal conditions, heart rate and blood pressure decrease during sleep. This allows the cardiovascular system to recover. During a so-called tropical night, however, the body continues to fight overheating:
- the heart rate remains elevated;
- blood pressure may not fall to normal nighttime levels;
- sleep becomes shallow and interrupted;
- the heart does not get the rest it needs.
After three or four such nights, the strain on the body accumulates.
The situation is particularly challenging in densely built urban areas. Asphalt, concrete surfaces, and building facades absorb heat during the day and release it at night. In some neighborhoods, temperatures may remain several degrees higher than in greener areas.
Who Is Particularly Vulnerable During Hot Weather
High temperatures can pose a risk to anyone, but the following groups should pay particular attention to their health:
- people over the age of 75;
- patients with high blood pressure;
- people with coronary heart disease;
- patients who have previously had a heart attack or stroke;
- people with heart or kidney failure;
- patients with diabetes;
- people with lung diseases;
- patients taking diuretics and antihypertensive medications;
- older people living alone;
- people who have to perform physical work in hot conditions.
According to data from the Swiss National Centre for Climate Services, 410 deaths were linked to heat exposure in the summer of 2025. Around 84% of those who died were over the age of 75. These figures show that heat is a real health risk rather than simply a seasonal inconvenience. NCCS Data
Symptoms That Should Not Be Ignored
Some people attribute feeling unwell to fatigue, age, or the weather. However, when cardiovascular disease is involved, delaying medical attention can be dangerous.
Seek immediate medical attention if any of the following symptoms occur:
- pressure, pain, or a burning sensation behind the breastbone;
- pain radiating to the arm, shoulder, back, neck, or lower jaw;
- sudden shortness of breath;
- cold sweats;
- severe weakness;
- nausea accompanied by chest discomfort;
- loss of consciousness;
- speech or movement difficulties;
- severe confusion;
- a very rapid or irregular heartbeat.
If a heart attack, stroke, or severe heatstroke is suspected in Switzerland, call 144.
Do not attempt to go to the doctor on your own or drive yourself. It is safer to call an ambulance and remain at rest until it arrives.
How to Protect Your Heart in Hot Weather
1. Avoid Physical Activity During the Hottest Hours
Walks, gardening, exercise, and trips are best scheduled for early morning or evening. The Swiss Federal Office of Public Health recommends avoiding intense physical activity approximately between 11:00 and 17:00.
2. Keep Indoor Spaces Cool
During the day, close windows, blinds, and shutters if it is hotter outside than indoors. Ventilate at night and early in the morning when the outdoor temperature drops. Switch off electrical appliances that generate additional heat.
3. Drink Regularly, but Follow Your Doctor’s Recommendations
In hot weather, it is important not to wait until you feel very thirsty. However, patients with heart or kidney failure should not suddenly increase their fluid intake without medical advice. The appropriate amount of water should be discussed with the treating physician in advance.
Alcohol and large amounts of sugary drinks are best avoided during hot weather.
4. Do Not Change Your Medication Dosage on Your Own
Diuretics, blood pressure medications, and certain other medicines can affect the body’s fluid and electrolyte balance and its ability to cope with heat.
However, stopping medication or reducing the dosage without medical advice can be dangerous. Treatment adjustments should only be made by a doctor.
5. Monitor Your Blood Pressure and Heart Rate
Older adults may benefit from having a reliable automatic blood pressure monitor at home. Blood pressure should preferably be measured while at rest and at approximately the same time each day.
If the readings differ significantly from your usual values or are accompanied by chest pain, shortness of breath, weakness, or dizziness, you should contact a doctor.
6. Help Your Body Cool Down
A cool shower, foot bath, or damp cloth placed on the neck can help lower body temperature. It is important to avoid ice-cold water and excessively rapid cooling, especially if you have cardiovascular disease.
Full recommendations are available on the website of the Swiss Federal Office of Public Health.
Why Preventive Screening Is Particularly Important
The danger of cardiovascular disease is that it can develop for a long time without obvious symptoms. A person may feel relatively well even though their blood pressure is already elevated and their coronary arteries are gradually narrowing.
A routine cardiological examination is particularly recommended if any of the following risk factors are present:
- a family history of heart attack or stroke;
- high blood pressure;
- high cholesterol;
- diabetes;
- excess weight;
- smoking;
- shortness of breath or chest discomfort during physical activity;
- heart rhythm disorders.
Depending on the patient’s condition, the examination may include blood tests, an ECG, an ultrasound examination of the heart, 24-hour blood pressure and heart rhythm monitoring, stress tests, or imaging of the coronary arteries.
Hot Weather Requires Greater Attention to Your Health
Prolonged periods of high temperatures are becoming an increasingly important medical issue in Switzerland. The greatest risk occurs when hot days are followed by warm nights and the heart does not have enough time to recover.
Simple measures — keeping indoor spaces cool, drinking regularly, monitoring blood pressure, taking medications correctly, and avoiding strenuous activity in the middle of the day — can genuinely help reduce the risk. However, they are not a substitute for medical diagnostics, especially if a person has already developed chest pain, shortness of breath, or sudden changes in blood pressure.
Prevention remains the best way to protect your heart. The earlier a problem is detected, the greater the chances of preventing serious complications.