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Higher outdoor temperatures linked to lower BP
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Daily temperature and humidity should be taken into account when monitoring BP levels, researchers concluded in a new study.
The study was designed to investigate associations between systolic and diastolic BP and climate parameters, including mean daily temperature and humidity, in a longitudinal cohort of 101,377 Dutch whole blood and plasma donors who made 691,107 visits to a blood bank from 2007 to 2009. Researchers measured BP before each blood donation and acquired climate parameters from the Royal Netherlands Meteorological Institute.
For every 1°C increase in mean daily temperature, systolic BP decreased by 0.18 mm Hg (95% CI, –0.19 to –0.16) and diastolic BP decreased by 0.11 mm Hg (95% CI, –0.11 to –0.1). The association remained after adjustment for confounders such as age, BMI, hemoglobin, smoking, antihypertensive drug use, sports participation, education, income and humidity (systolic BP, –0.17 mm Hg; 95% CI, –0.19 to –0.15; diastolic BP, –0.09 mm Hg; 95% CI, –0.11 to –0.08).
The researchers also found an association between each 1% increase in humidity and a rise in BP (systolic BP, 0.06 mm Hg; 95% CI, 0.05-0.07; diastolic BP, 0.04 mm Hg; 95% CI, 0.03-0.04); however, this finding was attenuated after adjustment for confounders including temperature (systolic BP, 0.00 mm Hg; 95% CI, –0.01 to 0.02; diastolic BP, 0.01 mm Hg; 95% CI, –0.00 to 0.01), according to results of a crude analysis.
Lower BP was most pronounced at higher temperatures and older age, according to the researchers. Predicted levels of systolic BP ranged from 134 mm Hg to 129 mm Hg with increasing temperatures for men aged 18 to 30 years vs. 145 mm Hg to 138 mm Hg with increasing temperatures for men aged 61 to 69 years. Predicted levels of systolic BP ranged from 124 mm Hg to 118 mm Hg with increasing temperatures in women aged 18 to 30 years vs. 140 mm Hg to 132 mm Hg in women aged 61 to 69 years. Predicted levels of diastolic BP ranged from 77 mm Hg to 75 mm Hg with increasing temperatures for men aged 18 to 30 years vs. 85 mm Hg to 82 mm Hg with increasing temperatures for men aged 61 to 69 years, and from 77 mm Hg to 74 mm Hg in women aged 18 to 30 years vs. 84 mm Hg to 80 mm Hg in women aged 61 to 69 years.
“Associations between mean daily temperature and blood pressure may partly explain the increased risk of [CV] mortality in extreme weather conditions. Improving climate control in houses or checking [BP] more frequently at extreme temperatures can potentially improve [BP] maintenance,” Katja van den Hurk, PhD, from the department of donor studies at Sanquin Research, Amsterdam, and colleagues wrote. “Seasonality should thus be taken into account when monitoring [BP] in daily practice and in studies on [BP] changes, particularly in older individuals.” – by Erik Swain
Disclosure: The researchers report no relevant financial disclosures.
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