A period of extreme heat is affecting multiple regions, with temperatures in Southeast Australia frequently exceeding 40ºC. Health authorities and medical organizations have issued guidance on the physiological risks associated with high temperatures, the impact of certain medications, and recommended safety measures for vulnerable populations, particularly older adults.
Physiological Impact of Extreme Heat
The human body primarily dissipates heat through the skin, which accounts for approximately 90% of heat loss via sweating and increased blood flow to the extremities. This process requires the heart to work harder to redistribute blood toward the skin.
According to Professor Ollie Jay, academic director at the University of Sydney's heat and health research centre, this increased cardiac effort can cause blood pressure to drop unless heart rate increases. Individuals with underlying heart conditions face a higher risk of heart attack under these circumstances.
Dr. Arnagretta Hunter, a cardiologist at the Australian National University, stated that warm evening temperatures resulting in a loss of overnight cooling can impact both physical and mental health, potentially leading to increased hospital admissions for cardiac and kidney problems, geriatric issues, and dizziness-induced falls.
Reported ambient temperatures, typically recorded in the shade by weather stations, can be up to 15°C lower than temperatures experienced in direct sunlight.
High humidity makes it more difficult for sweat to evaporate, hindering the body's primary cooling mechanism. Prolonged exposure to temperatures around 49°C or higher is considered unsafe.
Vulnerability in Older Adults
Older individuals face increased challenges in regulating body temperature due to age-related changes. Factors contributing to higher risk include:
- Reduced efficiency of blood flow to the skin and the body's sweating response
- Increased cardiovascular strain from the heart working harder to divert blood for cooling
- Age-related reduction in sweating ability, particularly for individuals over 75 years
- Social factors such as rising energy costs potentially deterring use of air conditioning, living alone, reduced mobility, or cognitive conditions like dementia
Medication Considerations
The Pharmacy Guild of Australia has issued guidance regarding certain common medicines that may increase risk during extreme heat. National President Professor Trent Twomey advised individuals to review and store medicines according to guidelines and consult a community pharmacist for concerns.
Medications for conditions including mental health disorders, ADHD, heart disease, high blood pressure, diabetes, migraines, allergies, and constipation can reduce the body's effective response to heat. Specific concerns include:
- Heart and diabetes medications potentially leading to acute kidney injury if dehydration occurs while continuing dosage
- Some antidepressants or ADHD medicines potentially reducing heat tolerance, increasing dehydration, or slowing the body's cooling process
- Certain non-prescription painkillers and antihistamines potentially affecting reaction to the sun
- Some medications heightening sensitivity to sunlight
The Guild advises individuals to continue using prescribed medicines while implementing extra precautions in hot conditions. Consumer Medicine Information (CMI) for prescription and some over-the-counter medicines provides details on possible side effects.
Medication Storage
Correct storage of medication is important, as active ingredients can degrade when exposed to extreme temperatures. Most tablets require storage below 30°C, or sometimes below 25°C, in a cool, dry place, such as a cupboard not exposed to direct sunlight.
Storing medication in a car's glove box is not recommended due to temperature fluctuations.
Certain medications, including insulin, weight-loss injections, and liquid antibiotics, require refrigeration. Free Home Medicines Reviews are available through GPs for medication management and storage.
Recognizing Heat-Related Illnesses
Heat Stress
Symptoms include tiredness, dizziness, weakness, muscle cramps, irritability, and general discomfort. In older adults, signs may include unusual tiredness, lethargy, loss of balance, confusion, shortness of breath, or changes in urine frequency or color.
Heat Exhaustion
Symptoms include core body temperatures up to 38°C, reduced sweating due to fluid loss, nausea, vomiting, headaches, and fainting. Heavy sweating, nausea, headache, and muscle cramps may be present.
Heatstroke
Core body temperatures can reach 40.5°C or exceed 40°C. Individuals may experience confusion, reduced alertness, hot and red skin, and absence of sweating due to severe dehydration. This is a medical emergency requiring immediate medical attention.
Safety Recommendations
Health authorities recommend the following measures:
- Consume adequate fluids and limit exposure to direct sunlight
- Utilize air conditioning, set to 26–27ºC for efficiency with a pedestal fan
- If air conditioning is unavailable, spend time in public cool spaces such as shopping centres or libraries
- For those without air conditioning, wetting the skin or clothing combined with a fan may boost evaporative cooling
- Immersing hands and forearms in cool tap water for ten minutes every half hour has been shown to lower body temperature and reduce cardiac strain
Community Response
Individuals are encouraged to check on older family members and neighbors during heatwaves. If anyone exhibits symptoms of heat stroke, such as slurred speech, confusion, fainting, or hot, dry skin, emergency services should be contacted immediately.