Hurricanes, flash floods and earthquakes may present as more directly threatening, but no weather kills more people each year than excessive heat, according to the National Weather Service.
From 1999 to 2023, annual heat-related deaths in the U.S. more than doubled to 2,325, according to a 2024 study published in the Journal of the American Medical Association. Heat stroke carries a 28-day mortality rate of 58%, according to a 2018 study published in the National Library of Medicine.
In light of that spike amid climbing temperatures, here to help you keep your cool in grappling with a heated issue is Dr. Christian Martin-Gill, an emergency medicine physician at UPMC.
Q: What happens to the body during a heat stroke?
A: During a heat stroke, there is an elevated core body temperature (typically greater than 40 degrees Celsius or greater than 104 degrees Fahrenheit) with associated dysfunction of the central nervous system (brain function).
This is different from an ischemic stroke, where there is a lack of blood flow to the brain, typically due to a clot in a blood vessel. Heat stroke causes a more global and often temporary impact on brain function, which, through early recognition and treatment, is often fully reversible.
Q: What triggers a heat stroke, what level of activity, body temperature or set of factors?
A: Heat stroke is often described as one of two entities: exertional heat stroke and classic heat stroke.
In exertional heat stroke, the body’s ability to thermoregulate (control its own temperature) becomes overwhelmed by the heat production generated during exercise. If heat gain generated by muscle contractions outmatches heat removal, the thermoregulatory system becomes overwhelmed and the body temperature elevates.
This thermoregulation can be particularly challenging when taking part in extended exercise in hot and/or humid environments, where typical heat dissipation methods, such as sweating, are less effective.
In classic heat stroke, a similar problem of temperature dysregulation can occur without excess activity when an individual is exposed to heat stress over a long period (days), often combined with medical conditions that make thermoregulation challenging.
Q: What are some of the best ways to prevent a heat stroke?
A: The first step is recognizing the environmental and physical conditions that predispose us to develop heat stroke.
We must be vigilant to help our bodies remain cool when exposed to excess heat, especially for extended periods, including wearing appropriate clothing for the weather, using shade and maximizing ventilation of closed spaces or active cooling (e.g., air conditioning).
When planning substantial exertion, it is important to recognize and compensate for extended-duration activity and the current weather conditions.
In either case, staying well hydrated is also important.
Q: What symptoms should people watch for?
A: Any change in mental status during exposure to heat or heavy exercise is a key factor to watch for. An individual may be slower to respond to questions, appear confused, or seem off-balance. In such an event, we should also consider other potential medical conditions, such as a stroke due to a blood clot in the brain.
Especially if there are changes in speech or one-sided weakness or numbness, ensure medical attention is sought immediately.
Q: What populations are most susceptible to heat stroke?
A: Individuals who are predisposed to heat stroke due to thermoregulatory challenges include those at extremes of age (older individuals or young children) and those with certain medical conditions, including certain neurological diseases and endocrine disorders.
Q: What are some common misconceptions about heat stroke?
A: It can be a misconception that heat stroke only happens on extremely hot days or when associated with excessive exertion. Sustained periods of heat with limited ability to cool can also represent a risk for heat stroke.
For example, elderly individuals without access to air conditioning in the home and who typically dress warmly could develop heat stroke when they are exposed to moderately elevated temperatures over multiple days with limited ventilation or other means of cooling.
Vigilance for such conditions is important.
Q: What is the range of outcomes for someone experiencing a heat stroke?
A: In most cases, with early recognition and treatment such as active cooling measures, a heat stroke is fully reversible. In rare instances, excessive heat exposure, especially over long periods, could cause more lasting damage to organs.
Q: What other conditions are brought on by the heat? How are they similar or different?
A: While heat stroke refers to the impact on brain dysfunction and its associated symptoms, exposure to excessively elevated core body temperature can impact multiple other organs. Individuals can experience severe dehydration, low blood pressure, shock, and damage to the kidneys or liver. These are similar in the need to promptly recognize that the body is not compensating appropriately for the heat exposure and/or exercise and the need to actively cool to reverse the effects. Depending on which organ system is impacted can have very different effects on the body.