High blood pressure is linked to cold wet weather

Two Scotland fans shield themselves from the rainy weather. Picture: Getty

A study by Glasgow University found that chilly conditions, low levels of sunshine and the rain all had an impact on patients’ blood pressure readings.

They also found that in those people whose blood pressure was most sensitive to the weather, the risk of dying increased by 35 per cent.

The study looked at more than 169,000 blood pressure measurements in more than 16,000 patients who attended the Glasgow Blood Pressure Clinic between 1970 and 2011.

These readings were then mapped against the weather in the area at the time to see whether they were affected by the conditions.

Dr Sandosh Padmanabhan, reader at the Institute of Cardiovascular and Medical Sciences, said the study showed for the first time that weather could  affect blood pressure and this varied between patients.

The researchers, writing in  the journal Hypertension, found that, on average, blood pressure readings in patients being treated for their condition dropped by 2 per cent a year if the weather was similar on two consecutive visits. But they found that if  temperatures dropped from their highest average level to  the lowest level between the two visits, then the patients’ blood pressure rose by 2.1 per cent.

A reduction in the level of sunshine also led to a 2.3 per cent increase in blood pressure, while higher air-frost increased measurements by 1.4 per cent and more rainfall pushed up readings by 0.8 per cent. But the researchers also found that patients differed in how much their readings were affected by the weather.

“Temperature-sensitive” patients showed worse blood pressure control during follow-up appointments and a 35 per cent increased risk of long-term mortality compared with patients not sensitive to the weather.

“We are treating the patients, we are trying to get their blood pressure down, but despite this, between the warmest and the coldest day, there is a 2 per cent increase in blood pressure,” Dr Padmanabhan said.

The researcher said the reasons behind the link included people feeling less stressed in nicer weather, as well as the effects of the cold on blood vessels.

“We know that in the warm weather people are happy and relaxed and blood pressures are lower,” he said.

“There are multiple reasons behind the effect.

“The cold weather will make all your blood vessels constrict and will increase your blood pressure because that is a reaction to cold.”

Dr Padmanabhan said the findings were important because if doctors were aware that a patient’s blood pressure was more likely to be affected by the weather, they could make the right decisions about treatment.

“In some cases, we may actually reduce treatment thinking  the blood pressure is low when actually it is just the weather having the effect,” he said.

But Dr Padmanabhan said his team did not think increased levels of high blood pressure in Scotland were due to the cold weather in the country.

“In Scotland, I think weather complicates treatment. I don’t think it increases the population prevalence of high blood pressure. That is due to lifestyle  primarily,” he said.