Risks of heatstroke for the elderly: causes and preventive measures

Heatstroke is a particularly big health risk for the elderly, with some sudden and severe cases leading to death. Here are some facts about the causes of heatstroke, and what can be done to prevent it.

Risk of indoor heatstroke

According to the Fire and Disaster Management Agency, about 71,000 people in Japan were taken to hospital in emergency transportation because of heatstroke between May and September, 2019. Of these cases, 38% took place at home.

Temperature and humidity levels in summer can often be higher indoors than they are outdoors. Such conditions make it easy to develop heatstroke, especially if room temperatures aren't properly controlled or if you aren't sufficiently hydrated.

There are three levels of severity for heatstroke. The first level causes symptoms such as dizziness, fainting, leg cramp, and stomach cramp. The second level can cause headache, nausea and vomiting, and exhaustion. Finally, severe cases include mental effects, seizures, and a general overheating of the body. This final category of heatstroke can lead to death.


Our bodies operate a system of constant regulation to maintain the ideal temperature. If the surrounding temperature increases, body temperature also increases and heat is released. If the surrounding temperature drops, so does our body temperature, as our body works to keep heat inside.

Heatstroke is what happens when our body becomes unable to make these adjustments and the temperature rises rapidly.

Our body also regulates its temperature by sweating. However, if we don't replace these fluids and mineral salts, it can lead to dehydration, another cause of heatstroke.

Risks for the elderly

Severe heatstroke is particularly dangerous for the elderly, and can often lead to death. Most people can tell when the temperature rises. However, this is difficult for the elderly, which means they can actually suffer a heatstroke before they even notice anything is wrong.

Sweating is also difficult for the elderly, which takes away a crucial method of temperature regulation. And since they often cannot detect thirst and their bodies carry less water than younger people, they are more prone to dehydration.

People who work outdoors, athletes who train during the day, children, and infants are also susceptible to heatstroke. Additionally, people who suffer from chronic illness, such as sequelae of stroke (cerebral infarction and cerebral hemorrhage) or diabetes, should be careful as their conditions make it difficult for their bodies to deal with heat (they don't feel temperature increases and they don't sweat).

First measure: preventing dehydration

Heatstroke can be prevented by taking appropriate measures. The most crucial points are to prevent dehydration and prevent the rise of body temperature.

On the first point, it is important to make sure you are sufficiently hydrated. Depending on age, about 50% to 70% of your weight is water. A loss of about 2% of this weight causes you to feel thirsty. About 3% causes symptoms such as loss of appetite, irritation, dry skin, and severe fatigue. If you lose 5% or more, you will have trouble communicating and breathing, and will experience dizziness and seizures. Throughout the course of a day, we are constantly losing fluids by sweating, urinating, and just breathing. Frequent hydration is the most effective way to prevent dehydration.

For the elderly, it is important to hydrate even when you don't feel thirsty. For example, a good measure to take is to drink a cup of water upon waking.

Additionally, it is recommended to take some form of an oral rehydration solution, composed of water and mineral salts, during summer. The salt helps compensate for the loss of water through sweat. Eating umeboshi (salted plum), salted kombu, and miso soup, among other foods, has the same effect.

Second measure: preventing the rise of body temperature

If room temperature increases while you're sleeping, you may have a heatstroke without even being awake. The ideal conditions are a temperature below 28°C and humidity below 70%. When you sweat, your body cools as heat is released from your skin. A high level of humidity prevents this sweat from evaporating. It is important to note that the use of a fan on its own is not enough.

How to cope with heatstroke

If you experience dizziness, head dullness, leg or stomach cramp, it is important to rest in a cool place, consume fluids and mineral salts, and loosen your clothing.

In addition, you should take steps to cool the blood vessels in your armpits, neck, and groin. If your condition doesn't improve, go to the hospital. Do not hesitate to call an ambulance once you notice more serious symptoms.

Heatstroke Risk Information