Heat Stroke Symptoms: Mental Changes You Should Never Ignore
When someone has been exercising, working, or spending a long time outdoors in extreme heat, a very high temperature is not the only thing to watch for. A sudden change in the way the person talks, thinks, walks, or responds can be a major warning sign of heat stroke.
A core body temperature of about 104°F (40°C) or higher is a classic finding in heat stroke. But if someone exposed to heat becomes confused, has slurred speech, cannot walk normally, has a seizure, or is difficult to wake, do not spend valuable time waiting for a perfect temperature reading. Heat stroke is a medical emergency that requires immediate cooling and emergency medical care.
Mental Changes Are Among the Most Serious Heat Stroke Symptoms
Heat stroke affects the brain as well as the body’s ability to control temperature. A person may suddenly seem confused or disoriented. They may not recognize familiar people or places, answer questions appropriately, or follow simple instructions.
Other neurologic symptoms can include:
- Slurred or unusual speech
- Irrational or unusual behavior
- Loss of coordination or stumbling
- Extreme drowsiness or difficulty waking
- Seizures
- Loss of consciousness
Headache, dizziness, nausea, weakness, and rapid breathing may also occur with heat illness. Those symptoms alone can occur with less severe heat-related conditions. A significant change in mental status after heat exposure should raise much greater concern for a medical emergency.
CDC guidance also emphasizes that heat stroke can progress rapidly and cause permanent disability or death when emergency treatment is delayed.
Sweating Does Not Rule Out Heat Stroke
Many people picture heat stroke as hot, completely dry skin. That can happen, particularly with classic heat stroke caused by prolonged environmental heat exposure.
However, someone can still be sweating heavily during heat stroke. CDC’s National Institute for Occupational Safety and Health lists both hot, dry skin and profuse sweating among possible heat stroke findings.
This is especially relevant after strenuous exercise or physical work. The CDC Yellow Book notes that exertional heat stroke can occur in healthy, physically fit people and is usually associated with profuse sweating.
So if a runner, construction worker, gardener, or anyone doing strenuous activity in hot weather becomes confused or loses coordination, sweating should not reassure you that the condition is only heat exhaustion.
Heat Exhaustion vs. Heat Stroke: What Is the Difference?
Heat exhaustion and heat stroke can share several symptoms, including headache, dizziness, nausea, weakness, thirst, and heavy sweating. The most useful distinction is how severely the nervous system is affected.
Here is a practical comparison:
| What to Check | Heat Exhaustion | Heat Stroke |
|---|---|---|
| Mental status | Usually alert, though irritability or mild confusion can occur | Marked confusion, abnormal behavior, seizures, coma, or major loss of coordination |
| Body temperature | May be normal or moderately elevated | Usually markedly elevated; about 104°F (40°C) or higher is a classic field finding |
| Sweating | Heavy sweating is common | Skin may be dry or the person may sweat heavily |
| Other symptoms | Headache, nausea, dizziness, weakness, thirst | Similar early symptoms plus major neurologic changes |
| Response | Move out of heat, cool, hydrate if able, and seek medical evaluation as appropriate | Call 911 and begin rapid cooling immediately |
The distinction is not always perfectly clear in the first few minutes. The CDC Yellow Book notes that mild mental changes can sometimes occur with heat exhaustion, while seizures, coma, and other major neurologic problems indicate heat stroke or another serious condition requiring urgent evaluation.
If the person is becoming less responsive rather than recovering after being moved to a cool environment, treat the situation as an emergency.
What to Do While Waiting for 911
Call 911 immediately when heat stroke is suspected, then start cooling the person. Do not wait for emergency medical services to arrive before beginning cooling.
Move the person into shade or an air-conditioned area and remove unnecessary outer clothing.
If possible, cool the body using one or more of these methods:
- Immerse the person in cold or cool water when it can be done safely.
- Wet the skin with cool water and continuously fan the person.
- Place cool, wet cloths over the skin.
- Apply cold packs or ice to areas such as the neck, armpits, and groin.
- Keep someone with the person until emergency medical services arrive.
Cold-water or ice-water immersion can provide especially rapid cooling for exertional heat stroke, but the person must be continuously attended to prevent drowning or other injury.
Do not give fever-reducing medicines such as acetaminophen or aspirin to treat heat stroke. They do not correct dangerous overheating.
Be particularly cautious about drinks. A person who is vomiting, unconscious, too confused to follow directions, or unable to swallow normally should not be given anything by mouth because of the risk of choking or aspiration.
Do Not Wait for the Thermometer if Behavior Has Changed
Temperature is useful information, and a core temperature around 104°F or higher strongly supports heat stroke. But in an emergency, obtaining a temperature should not delay calling 911 or cooling someone who develops severe confusion, slurred speech, loss of coordination, seizures, or loss of consciousness after substantial heat exposure.
Older adults, young children, people with cardiovascular disease, diabetes, kidney disease, and people taking certain medications may have greater difficulty tolerating extreme heat. Strenuous exercise, dehydration, and lack of heat acclimatization can also increase risk.
When someone in a hot environment suddenly stops acting like themselves, pay attention to the change in speech, behavior, coordination, and alertness. Call 911 when heat stroke is suspected and begin cooling immediately rather than waiting to see whether the person improves on their own.
Source:
Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health — Heat-related Illnesses
Centers for Disease Control and Prevention — CDC Yellow Book: Heat and Cold Illness in Travelers
National Library of Medicine, MedlinePlus Medical Encyclopedia — Heat Emergencies
