Blood pressure, or more specifically the pressure that blood creates when moving through the artery walls, is an important indicator that reflects the functioning of the circulatory system. Blood pressure index includes two parts: systolic blood pressure (the top number) represents the pressure in the arteries when the heart contracts to push blood, and diastolic blood pressure (the bottom number) represents the pressure during the period when the heart rests between beats.
According to the definition of the World Health Organization (WHO), a person is considered to have high blood pressure when the blood pressure index reaches 130/80 mmHg or higher (stage 1), or exceeds 140/90 mmHg (stage 2).
High blood pressure is not a single disease, but the result of many complex intertwined factors. It can arise from causes within the body, such as genetic factors, endocrine disorders or kidney diseases, called secondary hypertension.
Sometimes, this condition appears without a specific cause, called primary hypertension, which is often related to a high-salt diet, lack of exercise, smoking, drinking alcohol or prolonged stress.
However, there is one factor that many people do not pay attention to hot weather.
When the outdoor temperature increases, the human body does not remain passive but immediately deploys natural protective mechanisms to maintain stability. One of the first reactions is the dilation of blood vessels under the skin, helping the body “cool down” by bringing blood to the skin surface, where it can radiate heat to the environment. At the same time, the heart must beat faster to compensate for this blood distribution.
Although this is a normal physiological reaction, for people with a weak cardiovascular system, this can cause additional pressure, causing blood pressure to fluctuate significantly.
Who is most susceptible?
Not everyone has high blood pressure in hot weather. However, vulnerable groups include:
- Elderly people.
- Cardiovascular patients.
- People taking diuretics or blood pressure medications
- People working outdoors or exercising vigorously in hot weather.
How does the body react to hot weather?
1. Dehydration
Hot weather causes the body to sweat a lot, which means losing a significant amount of water and electrolytes. Mild dehydration can cause a decrease in blood volume, which lowers blood pressure in the short term. However, prolonged dehydration causes the heart to work harder to pump blood, leading to a counter-reaction that can cause blood pressure to suddenly increase. This is especially dangerous for the elderly or those taking diuretics – drugs that often cause dehydration more quickly than normal.
2. Risk of increased blood pressure at night
A little-known phenomenon is that hot weather can also increase blood pressure at night, when blood pressure is usually expected to decrease to help the body rest.
For some people, especially elderly patients, prolonged vasodilation during the day combined with dehydration can disrupt the blood pressure regulation mechanism at night. As a result, blood pressure at night does not decrease but increases, increasing the risk of stroke during sleep.
3. Endocrine disorders
Not only is it a physical problem, such as dilated blood vessels or dehydration, hot weather also causes hormonal fluctuations. When the body senses a temperature overload, the adrenal glands can release stress hormones such as norepinephrine and cortisol.
These two hormones have the effect of constricting blood vessels, increasing heart rate, thereby pushing blood pressure up. This reaction is a survival mechanism in emergency situations, but when it occurs frequently in prolonged hot conditions, it can become the cause of acute hypertensive crises, especially in people who already have unstable blood pressure.
What to do to protect blood pressure in hot weather?
Here are some useful tips that can help:
1. Drink enough water
When the outdoor temperature increases, our bodies will lose more water through sweat, causing blood pressure to fluctuate abnormally. To minimize the risk of high blood pressure in hot weather, one of the most important things is to ensure that the body is always adequately hydrated. Maintain the habit of drinking water regularly throughout the day, even when you are not thirsty. If you have to work or exercise outdoors for a long time, consider adding more water containing electrolytes to compensate for the loss of salt and minerals.
2. Limit exposure to sunlight
In addition, limiting exposure to harsh sunlight also plays an important role. The time between noon and early afternoon, from about 11am to 3pm is when the sun is at its strongest, so limit going out or make sure to take protective measures such as wearing sunscreen, a wide-brimmed hat and bringing water.
3. Check your blood pressure regularly
In addition, for those with a history of high blood pressure, it is advisable to proactively check your blood pressure daily during the hot season. If you feel any unusual symptoms such as dizziness, rapid heartbeat, unexplained fatigue or persistent headaches, do not hesitate to contact a medical professional for timely advice.
