Everyday · 5 min read
Who Is Most at Risk From Extreme Heat? Key Populations and Prevention
By TheCalcUniverse Editorial, Content Team · · Updated
The CDC lists seven groups at increased risk of heat-related illness: adults aged 65 and older, infants and young children, people with chronic medical conditions, people without air conditioning, athletes, outdoor workers and pregnant people. The groups fall into two types. Some people are at risk because their bodies cope with heat less well (age, health conditions, pregnancy, certain medications). Others are at risk because of what they are doing or where they live (exercise, outdoor work, no cooling at home). Many people belong to more than one group, and risks stack.
The CDC risk groups and the reasons given
| Group | Why the CDC says they are at higher risk | What to check |
|---|---|---|
| Adults 65 and older | Do not adjust as well to sudden temperature changes; more likely to have a chronic condition that changes normal responses to heat; more likely to take prescription medicines that affect temperature control or sweating | Working cooling at home, regular fluids, someone checking in on you |
| Infants and young children | Rely on others to keep them cool and hydrated | Shade, fluids offered regularly, never relying on a child to ask |
| People with chronic conditions | Hot days can be especially dangerous | A plan agreed with a clinician for hot weather |
| People without air conditioning | Need to prepare in advance for heat | A cool place to go, such as a friend's home or a public cooled space |
| Athletes | More likely to become dehydrated and get heat-related illness when exercising in heat | Training time, fluids, rest |
| Outdoor workers | More likely to become dehydrated and get heat-related illness | Water, rest, shade and a gradual start (see the OSHA article) |
| Pregnant people | Pregnancy can make illness more likely in very hot weather | Advice from the prenatal care team |
Medications that change how the body handles heat
The CDC's clinician guidance on heat and medications names several classes and the mechanism for each. The table repeats those entries. Only a clinician or pharmacist can say whether a specific medicine matters for a specific person.
| Medicine class | Mechanism the CDC lists |
|---|---|
| Diuretics | Electrolyte imbalance; volume depletion, dehydration and a higher risk of fainting and falls |
| Beta blockers | Reduced widening of blood vessels near the skin and decreased sweating |
| Calcium channel blockers | Lower blood pressure and a higher risk of fainting and falls |
| ACE inhibitors and ARBs | Reduced thirst sensation and a risk of low blood pressure |
| Lithium | Electrolyte imbalance and a risk of toxicity when dehydrated |
| Antipsychotics | Impaired sweating |
| SSRIs and SNRIs | Increased or altered sweating |
| Tricyclic antidepressants | Decreased sweating |
The CDC also lists antihistamines, stimulants, antiseizure medicines, NSAIDs and antibiotics among the classes with relevant effects. Its patient advice is to avoid stopping any medicine abruptly without a plan in place, to discuss adjustments for hot weather with a clinician, and to know when to seek medical care and which symptoms are an emergency.
Worked example: a home without cooling
Indoor heat is easy to underestimate. Suppose a home without air conditioning holds the following conditions during a heat wave. Heat index values come from the heat index calculator's formula, rounded to one decimal place. The formula was built for shade and light wind, so treat indoor figures as a rough guide.
| Indoor temperature and humidity | Heat index | NWS category |
|---|---|---|
| 82°F, 50% | 82.8°F | Caution |
| 86°F, 55% | 89.4°F | Caution |
| 90°F, 60% | 99.7°F | Extreme Caution |
| 88°F, 70% | 100.2°F | Extreme Caution |
The National Weather Service describes Extreme Caution as a category in which heat stroke, cramps or exhaustion are possible. That wording is for the general public. The calculator's own documentation notes that its number does not account for age, medications, obesity or acclimatization, so a person from one of the groups above can face real risk at a lower heat index than a healthy adult would.
Practical steps the CDC gives for older adults
- Stay in air-conditioned buildings as much as possible.
- Drink more water than usual and do not wait until you are thirsty.
- Wear loose, lightweight, light-colored clothing.
- Check on a friend or neighbor, and have someone do the same for you.
- Seek immediate medical attention for muscle cramps, headaches, nausea or vomiting.
Common mistakes and limits
- Assuming only the old and the very young are at risk. Athletes and outdoor workers are on the CDC list because exertion and dehydration are risks in themselves.
- Relying on thirst. The CDC tells older adults not to wait until they are thirsty, and it lists ACE inhibitors and ARBs with reduced thirst sensation.
- Stopping a medicine on your own in hot weather. The CDC advises against abrupt changes without a plan.
- Treating the heat index as a personal safety line. It is a general-public figure for shade and light wind.
- Skipping a check on neighbors who live alone. Checking on others is among the CDC's own recommendations.
- Expecting this article to give statistics. The CDC page cited here gives none for these groups, so none are quoted.
If someone becomes confused, slurs speech, has a seizure or loses consciousness in the heat, OSHA's guidance is to call 911 immediately and cool the person until help arrives.
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