Risk Factors for Heat-Related Illness and Cold-Related Illness

What “Risk Factors” Mean in Heat and Cold Emergencies

A risk factor is anything that increases the likelihood that a person will develop a heat-related illness (such as heat exhaustion or heat stroke) or a cold-related illness (such as hypothermia or frostbite). Risk factors matter in first aid because they help you predict:

• Who needs earlier intervention (cooling/warming sooner, more frequent checks)
• Who may deteriorate faster (lower threshold to call emergency services)
• Which first-aid choices are safer (for example, avoiding overly aggressive cooling/warming in certain people)

In practice, you will often see multiple risk factors stacked together (e.g., an older adult on a diuretic hiking in direct sun). The more factors present, the lower your “wait and see” tolerance should be.

Modifiable vs Non‑Modifiable Risks (and Why It Changes First Aid)

Non‑modifiable (you can’t change them today)

• Age extremes (infants/children, older adults)
• Pregnancy
• Many chronic illnesses
• History of prior heat illness
• Naturally low body fat

First-aid implication: treat earlier and monitor more closely. If symptoms appear, escalate sooner (earlier rest, shade/shelter, active cooling/warming, and earlier medical evaluation).

Modifiable (you can often change them now)

• Dehydration
• Poor fitness or lack of acclimatization
• Heavy clothing/PPE choices
• Alcohol use
• Planning errors (timing, route, breaks, buddy system)

First-aid implication: you can reduce risk immediately (fluids, clothing changes, schedule changes). If symptoms start, removing the modifiable stressor is part of treatment (e.g., stop exertion, remove excess layers, get out of wind/wet conditions).

Person‑Related Risk Factors

Age extremes

• Infants and young children: rely on adults for hydration, clothing, and pacing; may not communicate symptoms clearly.
• Older adults: may have reduced thirst perception, slower physiologic responses, and more chronic disease/medication use.

First-aid decision shift: use a lower threshold for active cooling/warming and for seeking medical care if symptoms are more than mild or do not improve promptly with rest and environmental change.

Continue in our app.

You can listen to the audiobook with the screen off, receive a free certificate for this course, and also have access to 5,000 other free online courses.

Or continue reading below...

Download the app

Pregnancy

Pregnancy increases vulnerability to both overheating and dehydration, and fainting risk may be higher with heat and prolonged standing.

First-aid decision shift: prioritize early cooling, hydration (if fully alert and not nauseated), and prompt medical advice if symptoms are significant, persistent, or accompanied by abdominal pain, contractions, or decreased fetal movement.

Chronic illness

• Heart disease or high blood pressure: may limit the body’s ability to compensate during heat stress or cold stress.
• Diabetes: can affect circulation and sensation; low blood sugar can mimic or worsen confusion and weakness.
• Kidney disease: increases risk from dehydration and electrolyte imbalance.
• Respiratory disease: cold air can worsen breathing; exertion in heat can strain breathing.

First-aid decision shift: monitor mental status and overall function closely. If the person has significant symptoms (confusion, fainting, chest pain, severe weakness), treat as higher risk and seek urgent medical care.

Prior heat illness

A previous episode of heat exhaustion or heat stroke increases the chance of recurrence, sometimes at lower heat exposure levels.

First-aid decision shift: intervene earlier (rest, shade, cooling) and avoid “pushing through.” If symptoms resemble prior severe illness, escalate quickly.

Dehydration

Dehydration reduces the body’s ability to handle heat and can also worsen cold risk by impairing circulation and decision-making. Common contributors include inadequate water access, vomiting/diarrhea, and high exertion.

First-aid decision shift: if the person is fully alert and able to swallow, prioritize oral fluids early. If altered mental status, repeated vomiting, or inability to drink is present, treat as higher risk and seek medical care.

Low body fat

Lower insulation increases cold vulnerability, especially in wind, wet conditions, or prolonged inactivity.

First-aid decision shift: start warming measures earlier and prevent further heat loss aggressively (dry layers, wind barrier, insulation from ground).

Poor fitness or lack of acclimatization

People not accustomed to heat, altitude, or sustained exertion often overheat sooner; those not used to cold may underestimate exposure and fail to layer appropriately.

First-aid decision shift: encourage pacing, scheduled breaks, and earlier symptom checks. If symptoms appear, stop exertion sooner than you might for a well-acclimatized person.

Medication/Substance‑Related Risk Factors

Medications and substances can change hydration status, heart rate response, alertness, and temperature regulation. In first aid, always consider whether a drug/substance could be making symptoms worse or masking them.

Diuretics (“water pills”)

Increase fluid loss and can contribute to dehydration and electrolyte imbalance, raising heat illness risk.

First-aid decision shift: be proactive about fluids and rest; treat early symptoms seriously. If the person becomes dizzy, confused, or weak, escalate care sooner.

Antihistamines

Some can reduce sweating and cause drowsiness, increasing heat risk and impairing judgment in both heat and cold.

First-aid decision shift: don’t rely on the person’s self-assessment alone; do more frequent check-ins for overheating or impaired coordination.

Beta‑blockers

Can blunt heart rate response and reduce the ability to compensate during exertion and heat stress; may also affect circulation in cold.

First-aid decision shift: use symptoms and function (weakness, dizziness, confusion) rather than heart rate as your guide; lower threshold to stop activity and cool/warm.

Alcohol

• Heat: promotes dehydration and impairs judgment.
• Cold: increases risk-taking and can worsen heat loss; intoxication can mask early warning signs.

First-aid decision shift: treat intoxicated individuals as high risk: earlier shelter, earlier active warming/cooling, and earlier medical evaluation if symptoms are more than mild.

Environment/Activity‑Related Risk Factors

Direct sun and radiant heat

Direct sun increases heat load even when air temperature feels tolerable. Dark surfaces and reflective environments (sand, water, pavement) intensify exposure.

First-aid decision shift: move to shade early; if symptoms appear, cooling steps should start immediately rather than waiting for “worse” signs.

Heavy clothing or PPE

Protective gear can trap heat and limit sweat evaporation; in cold, inadequate insulation or poor wind/water protection accelerates heat loss.

First-aid decision shift: prioritize safe clothing adjustments: remove or loosen heat-trapping layers in heat; add dry insulation and wind/water barriers in cold.

Wet and/or windy conditions

Wind and wetness accelerate heat loss and raise hypothermia risk even at cool (not freezing) temperatures.

First-aid decision shift: treat “cold + wet + wind” as a high-risk combination: get the person dry, sheltered, and insulated sooner than you might expect based on temperature alone.

Immersion (water exposure)

Water conducts heat away quickly. Cold-water immersion can lead to rapid loss of function and impaired self-rescue; even cool water can be dangerous over time.

First-aid decision shift: after rescue, prioritize removing wet clothing (when feasible), drying, insulating, and sheltering. Monitor closely for worsening symptoms during and after rewarming.

Prolonged inactivity

In cold environments, sitting still (spectator sports, waiting for transport, resting after exertion) reduces heat production and increases hypothermia risk. In heat, inactivity in a hot, poorly ventilated space (parked car, crowded room) can also be dangerous.

First-aid decision shift: don’t assume “not exercising” means “safe.” Change the environment (shade/ventilation or shelter/insulation) and check the person regularly.

Structured Pre‑Plan Checklist (Travel, Work, Outdoor Plans)

Use this checklist before you leave. If you answer “yes” to multiple items, adjust the plan (timing, clothing, pace, supervision) and set a lower threshold for stopping and providing first aid.

1) Person‑related checklist

• Is anyone an infant/child or an older adult?
• Is anyone pregnant?
• Does anyone have heart disease, diabetes, kidney disease, respiratory disease, or another chronic condition?
• Has anyone had a prior heat illness or a history of cold injury?
• Is anyone currently dehydrated (dark urine, very thirsty, headache) or recovering from vomiting/diarrhea?
• Does anyone have low body fat or get cold easily?
• Is anyone unfit for the planned exertion or not acclimatized to heat/cold?

2) Medication/substance checklist

• Is anyone taking diuretics?
• Is anyone taking antihistamines that cause drowsiness or reduce sweating?
• Is anyone taking beta-blockers?
• Will anyone be using alcohol before or during the activity?

3) Environment/activity checklist

• Will there be direct sun for long periods?
• Will anyone wear heavy clothing or PPE that limits ventilation?
• Are conditions wet and/or windy?
• Is there risk of immersion (boating, fishing, river crossing, cold surf)?
• Will there be prolonged inactivity (waiting, sitting, standing still)?
• Is there limited access to shade/shelter, water, or rapid exit/transport?

4) Plan adjustments (step-by-step)

1. Match timing to conditions: start earlier/later to avoid peak heat; in cold/wind, shorten exposure windows.
2. Set a hydration and food plan: carry enough fluids; schedule drink breaks; include salty snacks for long exertion (as appropriate).
3. Dress for control: in heat, choose breathable layers and plan PPE breaks; in cold, use layers plus wind/water protection and spare dry items.
4. Build monitoring into the plan: buddy checks every 15–30 minutes in higher risk situations; watch for behavior changes and coordination problems.
5. Define stop points: decide in advance when you will stop activity (e.g., headache + dizziness; shivering that persists; confusion; repeated stumbling).
6. Know your escalation route: identify nearest shelter, warming/cooling location, and how to contact emergency services.

How Risk Factors Change First‑Aid Decisions (Practical Scenarios)

Scenario A: Heat risk stacking

Situation: A 68-year-old on a diuretic is doing yard work in direct sun wearing long sleeves. They report headache and feel “a little woozy.”

• Non-modifiable risks: older age
• Medication risks: diuretic
• Environmental risks: direct sun, heavy clothing

Decision shift: treat as higher risk even if symptoms seem mild. Stop work immediately, move to shade, loosen/remove excess layers, begin cooling and oral fluids if fully alert. Monitor closely; if symptoms don’t improve promptly or worsen, seek medical care sooner than you would for a young healthy person.

Scenario B: Cold risk with wet/wind and low body fat

Situation: A thin teenager is watching a game in cold wind and drizzle, sitting still for an hour. They are shivering and becoming quiet and clumsy with their phone.

• Person risks: low body fat
• Environmental risks: wet + wind
• Activity risks: prolonged inactivity

Decision shift: don’t wait for “severe” symptoms. Move to shelter, replace wet clothing with dry layers, add insulation and wind barrier, and monitor coordination and alertness. Because function is changing (clumsiness/quietness), escalate earlier for medical evaluation if improvement is not clear and sustained.

Scenario C: Alcohol and immersion

Situation: An adult who has been drinking falls into cold water briefly and gets out, laughing it off, but later becomes unusually tired and slow to answer.

• Substance risks: alcohol
• Environmental risks: immersion

Decision shift: treat as high risk because alcohol can mask symptoms and impair judgment. Prioritize drying, insulating, and sheltering; monitor mental status. Lower threshold for emergency evaluation if confusion, persistent drowsiness, or worsening coordination appears.

Quick Reference: Risk Factor → Practical First‑Aid Priority