Certain populations are at higher risk for experiencing health problems in hot weather, explains Dr. Christopher F. Freer, senior vice president of emergency and hospital medicine at RWJBarnabas Health in New Jersey.
These populations include:
Infants, children, and the elderly who are unable to regulate their body temperature well or seek or consume fluids on their own, especially those with underlying medical conditions, pregnant women, and those with chronic illnesses
Still, no one is immune to health problems related to heatstroke, and understanding the signs can help you protect yourself (and those around you who may be at higher risk for more serious outcomes).
Below are six of the most common health risks that may increase as temperatures rise.
Migraine attacks
Data shows that migraine attacks affect 12-15% of the general population, and their effects can be debilitating.
“A migraine is not just a bad headache,” says Joshua Feinstein, MD, an emergency physician at Memorial Hermann Hospital.
A throbbing headache is one symptom, but other symptoms may include:
Sensitivity to light and sound, irritability, cravings, seeing or hearing strange shapes an hour before the migraine (aura), nausea, and dizziness
Recent studies suggest that heat may increase the risk of a migraine attack. For example, an observational study based on daily diary records of 660 migraine sufferers presented at the 66th American Headache Society Annual Scientific Meeting, held June 13-16, showed that heat may increase the risk of a migraine attack.
However, the findings have not yet been published in a peer-reviewed scientific journal.
A 2023 observational study of more than 40,000 respondents, including over 15,000 migraine sufferers, suggested that various weather types, such as high humidity, increase the occurrence of headaches.
“Heat can increase inflammation and prolong a migraine,” Feinstein says. “Plus, it can make you dehydrated, reducing your ability to fight off a migraine.”
Feinstein recommends that people who suffer from migraines, whether or not they are made worse by heat, work with a neurologist or other medical professional over the long term to minimize attacks and ease symptoms when they do occur.
heart attack
A 2023 study published in the journal Circulation suggests that heat-related cardiovascular disease deaths could increase by an estimated 162% by the middle of this century (2036-2065).
Another study conducted by Circulation in 2023 on over 202,000 heart attack deaths in Jiangsu province, China, showed a significant association between the likelihood of dying from a heart attack and extremely hot or cold temperatures.
“When exposed to heat, especially temperatures above body temperature, the heart has to work harder and beat faster because it needs to circulate blood towards the skin to enable sweating and other mechanisms the body uses to protect against the heat,” Luke says. “In at-risk individuals, the increased workload can lead to heart attack or other cardiac events.”
Feinstein said that while chest pain or pressure is the most common sign of a heart attack, other signs include:
Arm pain, shortness of breath, nausea, dizziness
“If you experience any of these symptoms, call 911 immediately and get out of the heat if possible,” Feinstein says.
stroke
A 2020 study suggested that weather conditions, including high temperatures, may be an emerging risk factor for stroke. The authors noted that there may be a lag period of one to six days between weather exposure and stroke.
Another study published the same year, but not yet published in a peer-reviewed scientific journal, suggested that for every 9°F increase in average three-day temperature, stroke severity increases by more than two-thirds (67%).
Loïc points to the same main reasons for the increased severity of strokes as for the risk of heart attacks.
“Extreme heat puts stress on the body, especially in older people, and may lead to increased stroke rates, especially in those with other risk factors such as high blood pressure,” Loic said.
According to Luke, symptoms of a stroke can include:
Weakness in an arm or leg (especially on one side) Changes in vision Drooping of the face Difficulty speaking Difficulty walking or feeling off balance
“If you have any of these symptoms, call 911,” Luke stresses. “Time is of the essence when it comes to treating a stroke.”
heatstroke
“Heat increases the risk of stroke not only by causing 'regular' strokes due to dehydration, but also by increasing body temperature, which can lead to heat stroke,” Feinstein explains.
Freer says that like a stroke, heat stroke is a medical emergency.
“Signs of heat stroke are confusion, changes in behavior, changes in speech and even seizures,” Freer says.
Heat stroke is not the same as heat exhaustion, although the two are related.
“Heat stroke is a warning sign that your body is getting too hot,” says Freer. “Symptoms like headache, dizziness and nausea are signs that you need to cool down and replenish fluids and electrolytes. Seek shade, rest and apply cool compresses.”
Freer also recommends avoiding caffeine and alcohol, which can make dehydration worse.
Worsening kidney disease
Kidney disease affects an estimated 37 million Americans, and a study published in 2022 suggested a significant association between kidney disease-related emergency department visits and exposure to extreme heat.
The study was based on more than one million kidney-related emergency room visits in New York City between 2005 and 2013. There was a strong association between the number of visits and the number of patients with acute kidney injury, kidney stones, and urinary tract infections.
“The kidneys are responsible for regulating the body's fluids, and excessive heat can cause excessive sweating, combined with other stressors on the body, which can exacerbate kidney problems,” Loïc says.
Plus, your kidneys need fluids to function, and when it's hot, you're at higher risk of dehydration, Feinstein explains.
High or low blood pressure
Fever can make your blood pressure either too low or too high.
“Hot weather can cause low blood pressure for a few reasons,” Freer says. “When you sweat profusely, your body loses fluid and blood volume. This decrease in volume can lead to lower blood pressure.”
The problem can be more noticeable when you change positions, like standing up after lying down, Freer said. Dizziness and lightheadedness are symptoms associated with low blood pressure.
Freer added that the strain dehydration puts on the kidneys can also cause blood pressure to drop, especially in people who are dehydrated.
Conversely, some people may experience an increase in blood pressure.
“Heat can cause an increase in blood pressure because your body has to work harder to keep you warm and circulate blood to encourage sweating and evaporation, which would otherwise cause your body temperature to rise, like heat stroke,” Loic says.
Loic says high blood pressure can be asymptomatic, but can also cause headaches and dizziness.
