The monsoon season has passed, bringing back stifling, suffocating heat. In this weather, heat-related illnesses become common, requiring heightened caution.
When the body's temperature regulation system fails in high heat, people frequently experience heat exhaustion. Typical symptoms include headache and lightheadedness, often accompanied by chest tightness, indigestion, and extreme fatigue.
However, summer dizziness is not always a temporary reaction to heat. It can also serve as a warning sign of a medical emergency caused by a blocked blood vessel in the brain.
Ischemic Stroke from Blocked Brain Blood Vessels: Can It Happen in Summer?
An ischemic stroke occurs when a blood vessel supplying the brain becomes blocked, preventing oxygen and nutrients from reaching brain tissue. If blood flow is not restored, tissue damage occurs, which can cause facial paralysis or loss of movement in an arm or leg.
While many associate ischemic strokes primarily with cold winter weather, patient numbers are actually higher during the summer months.
According to data from the Health Insurance Review & Assessment Service, 500,764 people received treatment for ischemic stroke in South Korea during the summer of 2023 (June to August), compared to 479,902 in the winter of that year (December to February)—a difference of over 20,000 patients. In 2025, summer patient counts (487,750) again exceeded winter figures (485,743).
Profuse sweating in summer heat can lead to dehydration, making the blood more concentrated and increasing the risk of blood clots (thrombi) that block cerebral vessels.
Furthermore, extreme heat causes peripheral blood vessels to dilate, leading to temporary drops in blood pressure. Older adults, individuals with pre-existing cerebrovascular risk factors, and those with narrowed cerebral arteries are particularly susceptible to vessel blockages.
Over the past three years, patients aged 60 and older accounted for 85.2% of cumulative ischemic stroke cases. Because aging impairs the body's ability to regulate temperature, older adults face a significantly higher risk of summer ischemic stroke and require extra vigilance.
Distinguishing Ischemic Stroke from Ordinary Dizziness
If an ischemic stroke occurs, emergency medical evaluation is necessary immediately. Missing the critical treatment window—often referred to as the 4.5-hour "golden time"—increases the risk of permanent brain damage and severe physical disability. Because dead brain cells cannot regenerate, rapid medical intervention is crucial.
"It is difficult to strongly suspect an ischemic stroke based on dizziness alone, but specific accompanying symptoms serve as critical warning signs," said Yoon Won-ki, Head of the Cerebrovascular Center at Korea University Guro Hospital.
According to Yoon, if sudden dizziness is accompanied by gait instability, diplopia (double vision), slurred speech, one-sided paralysis, or sensory loss, you should suspect an ischemic stroke and immediately seek emergency care or consult a neurologist or neurosurgeon.
Recognizing Key Warning Signs via the FAST Rule
To quickly identify the signs of an ischemic stroke, remember the FAST acronym:
F (Face, facial drooping): One side of the face droops when smiling, or the facial features appear asymmetric.
A (Arms, arm weakness): Weakness or numbness develops in one arm or leg.
S (Speech, speech difficulty): Speech becomes slurred, or the person struggles to form complete sentences.
T (Time, act quickly): Call emergency services (911) immediately and proceed to an emergency department if any of these symptoms appear.
Yoon emphasized that even if these symptoms resolve within minutes or hours, patients must not ignore them. Transient ischemic attacks carry a high risk of progressing to a full ischemic stroke within 48 hours of initial onset.
"When engaging in outdoor activities during the summer, drink lukewarm water frequently to prevent blood concentration, hydrating before you feel thirsty," Yoon advised. "However, patients with underlying conditions that require fluid restriction, such as heart failure or kidney failure, should consult their physician regarding appropriate hydration levels."
