As the temperature drops with winter, our blood pressure tends to go up. A normal blood pressure for most adults is less than 120/80 millimetres of mercury (mmHg), where the first number is the systolic pressure (the pressure in your arteries when your heart beats) and the second is the diastolic (the pressure in your arteries when your heart rests between beats). Considering Indians have multiple co-morbidities — obesity, diabetes, cholesterol, genetic history — which can amplify your BP, they need to keep readings within this range or even lower.
Why BP goes up in winter
Cold weather constricts blood vessels to conserve body heat. This makes it harder for the blood to flow and increases blood pressure. Pollutants like PM2.5 and PM 10 have the same narrowing effect.
People tend to eat more, exercise less and gain some weight in winter, which can elevate blood pressure. Vitamin D deficiency, because of poor sunlight exposure, can increase the risk of hypertension. Also, since you sweat less in colder temperatures, you retain salt, which in turn makes your body retain water. This increases blood volume and consequently blood pressure.
Why is even the smallest BP rise bad for your heart?
If your BP is even slightly higher than 120/80 mmHg, and you have another risk factor like diabetes (Indians usually do), then the risk of heart attack goes up by two-fold. If you have multiple risk factors like obesity or cholesterol, then the combined risk goes up by up eight-fold.
High BP makes the heart work harder to pump blood, which can thicken and enlarge the left ventricle or lower chamber. It can damage blood vessel walls, triggering tears and blood clots. Cholesterol and fats build up over the tears, forming plaque. This buildup can narrow arteries and block blood flow to the heart. Or high blood pressure may just dislodge the plaques that block blood flow, triggering a heart attack.
HOW TO MANAGE YOUR BP LEVELS IN WINTER
Manage other conditions like diabetes and keep them in range. Focus on sleep hygiene and other lifestyle course correctives like diet (watch that salt) and exercise (try increasing the quota to avoid calorie and fat buildup).
If your BP is elevated, go in for daily monitoring. Record readings twice a day for a week, once in the morning without medication and again in the evening after it. Once your BP has stabilised, a weekly check is ideal.
Do not take tea or coffee half an hour before measuring your BP. Take three readings after lying down and work out an average. Consult a doctor if the reading is high. Sometimes, you may have to increase the dosage of a BP pill in winter.
(Dr Shetty is interventional cardiologist at Manipal Hospitals, Bengaluru)