Low temperatures can cause sudden high blood pressure, increase blood viscosity, reduce oxygen to the brain, and raise the risk of stroke.
Dr. Vu Van Nam, a specialist in neurology and stroke at Tam Anh General Hospital in Hanoi, states that the incidence of stroke tends to increase during cold weather, particularly in the elderly and those with underlying health conditions. Strokes often occur around midnight and early morning when temperatures drop more significantly than at other times.
Dr. Nam points out several reasons why cold weather increases the risk of stroke:
Vasoconstriction and sudden high blood pressure: In low temperatures, the body reacts by constricting peripheral blood vessels (the vessels that carry blood from the heart to distant organs) to retain heat and concentrate blood flow to vital organs. This leads to increased blood pressure, which exerts significant pressure on the circulatory system. High blood pressure can also strain blood vessels, causing them to rupture—one of the leading risk factors for hemorrhagic stroke. Cold weather stimulates the sympathetic nervous system, increasing the secretion of hormones like adrenaline, which causes vasoconstriction, increases heart rate, and burdens the cardiovascular system, particularly in individuals with a history of heart disease or hypertension.
Increased blood viscosity: In colder weather, blood thickens and becomes more viscous to retain body heat, raising the risk of blood clots forming in the blood vessels. These clots can obstruct blood flow to the brain, leading to ischemic stroke.
Increased heart rate: As temperatures drop, the body generates additional heat to stay warm, resulting in an increased heart rate to pump blood faster and maintain body temperature. A high heart rate places additional strain on the heart, potentially leading to arrhythmias or other cardiovascular events related to stroke. For those with cardiovascular diseases, prolonged overexertion of the heart can easily result in myocardial infarction or stroke.
Hanoians in the cold of January 2024. (Illustrative photo: Giang Huy).
Reduced oxygen to the brain: Cold weather results in dry air, which decreases the efficiency of oxygen exchange in the lungs. When the brain does not receive enough oxygen, the risk of stroke increases, particularly for individuals with chronic lung or cardiovascular diseases.
Unhealthy habits: Winter brings shorter days and longer nights, which can disrupt biological rhythms due to a lack of sunlight. People tend to reduce physical activity and alter their sleep patterns, affecting blood pressure and metabolism, thereby indirectly increasing the risk of stroke. Dr. Nam notes that consuming high-fat and high-salt foods can easily elevate blood pressure and lead to obesity—two significant risk factors for stroke.
Stroke is an acute condition that occurs suddenly, with a high rate of mortality and disability complications. To reduce the risk of stroke during cold weather, Dr. Nam advises everyone to keep warm, especially around the head and neck, dress appropriately, and wear scarves and gloves when going outside. Regularly monitor blood pressure, especially in the elderly or those with a history of hypertension, diabetes, or dyslipidemia.
Maintain a healthy diet (limit alcohol, fried foods, and fast food), and increase indoor exercise for about 30 minutes daily. Stay hydrated even when not feeling thirsty, as the body needs sufficient water for good blood circulation. Regular stroke screenings during cold weather help protect health and proactively prevent issues.
If individuals experience symptoms such as weakness in limbs, numbness in arms or legs, difficulty speaking, facial drooping, or sudden dizziness, they should quickly seek treatment at the nearest stroke treatment facility for timely diagnosis and care. The “golden hour” for stroke emergency treatment is within 4.5 hours from the onset of symptoms. Early treatment significantly increases the effectiveness of care.
