Cold weather triggers several physiological responses that can increase stroke risk, even in healthy individuals. Deep cold causes blood vessels to constrict, elevating blood pressure as the body tries to conserve heat. Concurrently, dry air leads to subtle dehydration through skin and breath, thickening the blood and increasing its viscosity. This forces the heart to work harder to maintain circulation. The combination of high blood pressure and constricted vessels can rupture cerebral vessels or dislodge atherosclerotic plaques, forming blood clots that may cause myocardial infarction or stroke.
The risk is significantly higher for individuals with pre-existing conditions like cardiovascular disease, diabetes, or dyslipidemia. High blood pressure, often called a "silent killer" due to its lack of obvious symptoms, is a primary cause of stroke, capable of inducing both ischemic and hemorrhagic types.
Furthermore, certain lifestyle habits can heighten this risk. Blood viscosity peaks in the early morning. Exercising outdoors on an empty stomach, without hydration, or sudden exposure to cold air can promote blood clot formation. These clots can then travel to the brain, causing blockages, or impede blood flow to the heart, leading to coronary artery occlusion. Many healthy individuals often overlook these subtle internal changes, believing they are immune.
Other dangerous factors include stress, insomnia, and overwork. Stress triggers the release of cortisol and adrenaline, accelerating heart rate. Poor sleep compromises the body's ability to regulate blood sugar, further contributing to risk.
To mitigate these risks, individuals should adopt preventive measures. Drink a cup of warm water upon waking to help thin the blood, and consume a light meal to stabilize blood sugar. When venturing outdoors, ensure the neck, chest, and limbs are adequately warmed. Elderly individuals or those with underlying conditions should delay outdoor exercise until after 6 am when temperatures are milder, or opt for gentle indoor activities.
Doctor Doan Du Manh
Vietnamese Society of Vascular Diseases
