Research from around the world shows the blood pressure rises during winter and falls during summer months. Cold weather is consistently associated with higher blood pressure in all groups of people studied, including health adults without hypertension, people already diagnosed with high blood pressure, children and the elderly.
How much does blood pressure rise during cold weather?
How you respond to cold weather will depend partly on your age, your general health, diet and lifestyle, as well as any medication you are taking.
A study involving over 55,500 healthy people without high blood pressure, found that every 10°C decrease in temperature was associated with an average 1.85/1.18 mmHg increase in blood pressure. Blood platelets (a measure of stickiness) also increased, although levels of LDL-cholesterol went down (perhaps burned to help warm the body).
A French study found that blood pressure varied significantly across the seasons, and was 149/82.1 mmHg in winter compared with 144/81 mmHg in summer. On average, blood pressure was 8/3 mmHg higher when temperatures were below 7.9°C than when they were 21.2°C or above, for example.
Researchers in Glasgow assessed over 169,000 blood pressure measurements from 16,010 patients who attended a blood pressure clinic over a 40 year period, and mapped each patient’s blood pressure measurement against prevailing weather conditions to assess the effect of weather. They found that in people who were weather sensitive, blood pressure was 2.68/1.85 mmHg higher during cold/frosty weather than when the sun was shining, although not everyone appeared to be temperature sensitive.
In contrast, a study in Africa, where people are used to warmer weather, found that a decrease in environmental temperature of 10 degrees C (from 25°C to 15°C) increased average blood pressure measurements by an astonishing 32/19.5 mmHg!
Why cold weather increases blood pressure
The fact that blood pressure rises during cold weather may be part of an ancient survival mechanism that activates the sympathetic nervous system and increases secretion of stress hormones (such as noradrenaline, adrenalin and cortisol). This causes blood vessel constriction and a rise in blood pressure in response to cold temperatures to help conserve heat and body temperature.
It doesn’t take long for blood pressure to rise when you are cold, either – significant rises are seen within five minutes exposure to temperatures of 11 Degrees C (52 degrees F) for example. Experiments in which volunteers plunged one hand into freezing water for one minute show that the subsequent rise in blood pressure lasts for up to two hours.
Recent research suggests that cold sensitivity may be linked with a receptor that is activated by the vessel-constricting hormone angiotensin. It’s therefore possible that people taking an ACE inhibitor drug may be less sensitive to the effects of cold weather.
Other winter factors are also involved in blood pressure increases, however, including:
- reduced sun exposure and falling levels of vitamin D
- a tendency to take less physical exercise
- cold causes blood to thicken and become more sluggish
- increased levels of atmospheric pollution from burning fuels
- winter viruses such as colds an ‘flu
- the stress of returning to work after winter holidays.
All these effects, combined, may explain why cold temperature is a key risk factor for heart attack and stroke.
How to overcome cold weather
Dress up warmly indoors using layers of clothing, warm underwear and woolly socks.
Put a blanket over your knees when sitting down.
Use a hot water bottle.
Follow a DASH diet with more fruit and vegetables, less salt and alcohol.
Exercise regularly, on most days.
Wrap up warm when going out, with scarf, hat, gloves, wind proof coat etc.
Check your blood pressure regularly with a home monitor.