Heat stroke risk factors: who is more likely to get sick from the heat

What heat stroke is

Your body normally cools itself by sweating. During hot weather, especially when it is very humid, sweating just isn't enough to cool you off, and your body temperature can rise to dangerous levels (MedlinePlus).

Heat stroke is the most serious heat-related illness. It occurs when the body can no longer control its temperature: the temperature rises rapidly, the sweating mechanism fails, and the body is unable to cool down. Body temperature can rise to 106°F or higher within 10 to 15 minutes, and heat stroke can cause permanent disability or death if the person does not receive emergency treatment (NIOSH).

Who is at higher risk

Hot days can affect anyone, and anyone at any time can suffer from heat-related illness, but some people are at greater risk than others (CDC). The CDC lists these groups (CDC):

• Older adults (aged 65 and older), who are more prone to heat-related health problems (CDC).
• Infants and young children, who rely on others to keep them cool and hydrated when it's hot outside (CDC).
• People with chronic medical conditions, for whom hot days can be especially dangerous (CDC). The CDC names people, especially children, with asthma and people with heart disease among the groups that may need to take additional action on hot days (CDC).
• People without air conditioning at home (CDC).
• Athletes: people who exercise in heat are more likely to become dehydrated and get heat-related illness (CDC).
• Outdoor workers, who are more likely to become dehydrated and get heat-related illness (CDC). NIOSH adds that both outdoor and indoor workers exposed to extreme heat or hot environments may be at risk (NIOSH).
• Pregnancy, which can make you more likely to get sick when it's very hot (CDC).

MedlinePlus adds that most heat illnesses happen when you stay out in the heat too long. Older adults, young children, and those who are sick or overweight are most at risk, and taking certain medicines or drinking alcohol can also raise your risk (MedlinePlus). People who live alone are another group the CDC asks you to check on during hot weather (CDC).

Medicines and heat

Many medicines can make you dehydrated or overheated on hot days, and some need to be kept out of hot places. Don't stop or change your medicines until you talk to your doctor, and have a plan for refrigerated medicines and electronic medical devices in case heat causes a power outage (CDC). The CDC suggests working with your doctor to create a Heat Action Plan (CDC).

Heat stroke and other heat illnesses

• Heat stroke: confusion, altered mental status, slurred speech; loss of consciousness; hot, dry skin or profuse sweating; seizures; very high body temperature. It can be fatal if treatment is delayed (NIOSH). MedlinePlus also lists a rapid, strong pulse, dizziness, and nausea, and says to get medical help right away if you see any of these signs (MedlinePlus).
• Heat exhaustion: the body's response to an excessive loss of water and salt, usually through heavy sweating. Symptoms include headache, nausea, dizziness, weakness, irritability, thirst, heavy sweating, elevated body temperature, and decreased urine output (NIOSH). If it is not treated, it can turn into heat stroke (MedlinePlus). NIOSH advises taking a worker with heat exhaustion to a clinic or emergency room for evaluation, and calling 911 if medical care is unavailable (NIOSH).
• Rhabdomyolysis: linked to heat stress and long physical exertion, it causes rapid breakdown of muscle and can lead to irregular heart rhythms, seizures, and kidney damage. Signs include muscle cramps or pain, dark (tea or cola-colored) urine, and weakness; seek immediate care at the nearest medical facility (NIOSH).
• Heat syncope: fainting or dizziness, usually when standing too long or standing up suddenly. Dehydration and not being used to the heat (lack of acclimatization) may contribute (NIOSH).
• Heat cramps and heat rash: muscle pains or spasms during heavy exercise, and skin irritation from excessive sweating, which is more common in young children (MedlinePlus).

Lowering your risk on hot days

You can lower your risk of heat illness by drinking fluids to prevent dehydration, replacing lost salt and minerals, and limiting your time in the heat (MedlinePlus). The CDC also suggests staying in the shade and taking breaks, doing outdoor activities during the coolest parts of the day, using air conditioning or finding a cooled place (dialing 2-1-1 can help), and using fans only if indoor temperatures are below 90°F, because above that a fan can increase body temperature (CDC). Check on family, friends, and neighbors, especially if they live alone or have chronic medical problems (CDC).

Common questions

Who is most at risk for heat stroke?

The CDC lists adults aged 65 and older, infants and children, people with chronic conditions, people without air conditioning, athletes, outdoor workers, and pregnant people (CDC). MedlinePlus says older adults, young children, and those who are sick or overweight are most at risk (MedlinePlus).

What are the risk factors for heat exhaustion?

The same groups are at higher risk for heat-related illness in general (CDC). Heat exhaustion can happen after several days of exposure to high temperatures and not enough fluids (MedlinePlus), and it comes from an excessive loss of water and salt, usually through heavy sweating (NIOSH).

Can medicines raise the risk of heat illness?

Yes. Taking certain medicines can raise your risk (MedlinePlus), and many medicines can make you dehydrated or overheated on hot days. Talk to your doctor before stopping or changing any medicine (CDC).