Extreme heat is becoming more frequent. For most people, it might just bring fatigue or a loss of appetite. But for the elderly and those with heart disease, high blood pressure, diabetes, or kidney disease, high temperatures are a serious health threat—adding strain to the heart and potentially leading to life-threatening complications.
Cooling the Body Relies on the Heart – Heat Loads It Heavily
Many assume hot weather just makes you sweat. In reality, when it's hot, the heart becomes the organ under the most strain to maintain normal body function. The body cools itself through two mechanisms: sweating and dilating blood vessels near the skin's surface to release heat.
Think of the skin as a large radiator and the heart as a steady pump. Normally, the heart pumps blood to the body at a steady pace. But in extreme heat, the heart must supply blood to vital organs—like the brain and kidneys—while also sending more blood to the skin to release heat. This speeds up the heartbeat and increases cardiac workload. Even when resting, in a hot, stuffy environment, the heart is essentially "working overtime."
Dehydration Triggers Heat Stress and Cardiovascular Risk
Another challenge is dehydration. "Heat stress" refers to the extra burden high temperatures (especially with high humidity) place on the body. When you sweat too much without drinking enough, blood volume drops, causing blood pressure fluctuations and increasing the risk of electrolyte imbalance. When electrolytes are imbalanced, irregular heartbeats can occur, straining the heart and blood vessels further.
For those with existing cardiovascular conditions, this is especially dangerous. Dehydration makes circulation less efficient, forcing the heart to pump harder. Combined with blood pressure changes, this can worsen existing conditions and increase the risk of heart failure, heart attack, or stroke.
High-Risk Groups: The Elderly and Those with Chronic Illnesses
The elderly are particularly vulnerable to heat. As we age, the body's ability to regulate temperature declines, and the sensation of thirst may weaken. So even if the body is already dehydrated, an older person may not feel thirsty right away. If they also have mobility issues, live alone, or have chronic conditions, the risk of heatstroke and cardiovascular complications is even higher.
For example, a 70-year-old with high blood pressure and heart failure might feel dizzy, have a racing heart, and become short of breath after shopping at noon. They might think, "It's just too hot—I'll sit down for a bit." But these could be warning signs. For those with weaker cardiovascular function, delaying action can cause rapid deterioration.
Recognise the Warning Signs – Don't Just Blame the Heat
In hot weather, ignoring early symptoms can lead to rapid worsening. Watch for these signs:
-
Heat Exhaustion Signs: Dizziness, headache, weakness, nausea, cramps, fast heartbeat, or heavy sweating. Move to a cooler or air-conditioned place immediately, rest, rehydrate, and cool down.
-
Heatstroke or Acute Heart Issues: If symptoms worsen—confusion, hot skin, difficulty breathing, chest pain, or loss of consciousness—call an ambulance immediately. Heart patients should never dismiss chest discomfort or breathing difficulty as just "feeling stuffy."
3 Essential Summer Heart Care Tips
Prevention is key to reducing the heart's heat-related burden:
-
Avoid peak heat hours: Midday to afternoon is usually the hottest part of the day. If possible, schedule outings, walks, exercise, or clinic visits for early morning or evening.
-
Hydrate regularly: Develop a habit of drinking small amounts frequently—don't wait until you're thirsty. Avoid alcohol, excessive caffeine, and sugary drinks, which can speed up fluid loss. However, those with heart failure or kidney disease should follow medical advice on fluid intake.
-
Keep the environment cool and reach out: Ventilate the room, close curtains to block direct sunlight, and use air conditioning or fans when needed. If you have elderly relatives living alone, check in on them regularly, remind them to drink water, and watch for any changes.
Staying cool isn't just about comfort—for the elderly and those with chronic illnesses, it's a critical heart-protective measure. For every degree the temperature rises, the heart works harder. With extreme heat becoming more common, early action—staying hydrated, avoiding peak heat, and monitoring health—is essential. In summer, a little extra vigilance goes a long way in protecting both your own health and that of your family.
Author: Dr. Yeung Wai-lam, Senior Lecturer, School of Nursing and Health Studies, Hong Kong Metropolitan University
