Patients with newly diagnosed hypertension may be at risk of under-treatment if their therapy begins in winter according to a new study linking changes in blood pressure levels by season.
Researchers from The George Institute of Global Health in Sydney who conducted the study looked at blood pressure measures of 2.6 million patients aged 30-90 years with at least one blood pressure measure recorded over a seven-year period.
The findings are due to be presented as a poster session at the ACC.20 virtual conference being held next week show that blood pressure varied seasonally, with 3mmHg higher systolic blood pressure in winter.
It was a pattern seen across the whole population, observe investigators, affecting both older and younger patients, men and women and whether patients were on blood pressure lowering therapies or not.
Speaking to the limbic epidemiologist and study lead Dr Emily Atkins says the ‘moderately large’ changes in blood pressure by season are especially relevant to diagnosis and management with the study also showing that treatment intensity did not change over the study period to reflect these seasonal variations, says in an interview with the limbic.
“We looked at the use of blood pressure lowering medicines and if that use changes seasonally as well and while we didn’t see change in treatment intensity – how much we expect a particular drug and dose combination to reduce a person’s blood pressure – overtime we did see a difference in intensity in those newly diagnosed people who start treatment in January versus those who commence treatment in July,” she notes.
The fall in blood pressure with warmer weather during the first few months of therapy could lead to overestimation of regimen efficacy, she adds.
“If the treatment-intensity change is happening at a time when a patient’s blood pressure is going up because of seasonality heading into the cooler months you will probably end up with more effective treatment than if a patient was to commence treatment in July and go on to have their dose titrated some six weeks later as the weather begins warming up again and blood pressure, responding seasonally, comes down,” she explains.
“In that case you would end up with a less effective treatment being prescribed.”
A possible explanation for the cold weather effect could include vasodilation, adds Dr Atkins.
“When its hot you’re blood vessels dilate to help cool you down and when it’s cold they constrict to help keep you warm and that constriction may be what’s contributing to higher blood pressure readings.”
Meanwhile the European Society of Hypertension released a consensus statement on seasonal variation in blood pressure earlier this year – the first time there has been some ‘proper consideration’ of seasonal changes and how they might affect people with high blood pressure, Dr Atkins notes.
The European Society of Hypertension recommends seasonal blood pressure changes be confirmed by repeated office measurements, preferably with home or ambulatory monitoring, and adds that other reasons for blood pressure change must be excluded.
Similar issues might appear in people traveling from cold to hot places, or the reverse, it adds.
Meanwhile, blood pressure levels below the recommended treatment goal should be considered for possible down-titration, particularly if there are symptoms suggesting overtreatment.
The poster can be viewed here as part of the American College of Cardiology and World Congress of Cardiology 2020 virtual conference.