How Does Hot Weather Affect Your Blood Pressure ?

How Does Hot Weather Affect Your Blood Pressure

How Does Hot Weather Affect Your Blood Pressure

The warm weather we have been experiencing for the past week is set to stretch into the next two weeks of May.

With temperature expected to stay high in the next few weeks, many people will have occasional moments of feeling giddy. This may happen all the more so in people who are struggling to control their blood pressure.

In principle, the body is geared to towards maintaining a stable balance for existence. However, in situations where the outside conditions change a lot, the balancing program may be overwhelmed. This often happens when the body’s blood pressure maintenance is influenced by both medication and weather conditions at the same time.

As the weather gets hot, our body tries to lower the core temperature. We do that by sweating. In order to sweat, the body will need to bring fluid to the skin and give the skin better blood perfusion. As such, the smallest blood vessels, otherwise known as capillaries, will be widened as compared to normal situations. This is why we often get red shiny faces in hot weather.

On the other hand, blood pressure needs to be maintained. Blood pressure maintenance can be described as an interplay of various systems that would be hormonal, nervous and chemical in nature. But ultimately, it always come back to the most basic theory – that blood pressure is defined through equations rooted in physics.

At this level of physics, there is an interplay between the three key factors:

  • Volume of blood (cardiac output);
  • Speed at which this volume goes through a tube (the heartrate); and lastly
  • The resistance the volume encounters (vascular resistance)

Hence, if somebody with usually well controlled blood pressure encounters very hot weather conditions and the body wants to maintain the body temperature, the body can do so by widening the peripheral capillaries. And when that happens, the previously stable amount of blood volume and stable heart rate will flow into a tube system of lower resistance. As a consequence, blood pressure will drop.

This is why in the hot weather conditions, blood pressure levels are typically measured lower than in cold weather conditions. In northern countries, where there is a big difference between the summer and winter months, patients are often advised to change their blood pressure medication according to the seasons.

Singapore usually has a more stable overall weather. Thus, seasonal adjustment of the blood pressure medication is usually not necessary and not common.

However, if the weather becomes quite extreme, as we have experienced in the last few days where my outside thermometer showed as high as 37°C, people on hypertension medicine that gives them giddiness these days should carefully measure their blood pressure and ask the doctor if they may need to reduce the medication for a short while as the weather remains so hot.


About Dr Adrian Mondry

Dr Adrian Mondry is a Hypertension Specialist accredited by the German Hypertension League in Singapore.

He was previously a senior consultant in the department of medicine at the National University Hospital and Ng Teng Fong General Hospital (NTFGH), Dr Mondry has more than 30 years of experience in the field of internal medicine.

Dr Adrian Mondry is recognised for his leadership and contributions in establishing the dedicated hypertension clinic within the National University Health System and fast-track deep vein thrombosis service at NTFGH.

Dr Adrian Mondry is fluent in English, German and French.

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