A French study reported in the 12th January issue of Archives of Internal Medicine has found a strong correlation between blood pressure and outdoor temperature in a large sample of the elderly.(1) As a result, the investigators advise that, during periods of extreme temperatures, careful monitoring of blood pressure and antihypertensive treatment "could contribute to reducing the consequences of blood pressure variations in the elderly".
The study, which monitored 8801 participants over the age of 65 in the French Three-City study, found that systolic and diastolic blood pressure values differed significantly across the four seasons of the year and according to the distribution of outdoor temperature. The higher the temperature, the greater the decrease in blood pressure. Systolic blood pressure, for example, decreased with increasing temperature, with an 8.0 mmHg decrease between the lowest ( < 7.9C) and the highest (21.2C) temperatures. Average systolic blood pressure was 5 mmHg higher in winter than in summer. High blood pressure, defined as a systolic blood pressure of 160 mmHg or higher, or a diastolic blood pressure of 95 mmHg or higher, was detected in 33.4 per cent of participants during winter and 23.8 percent during summer. These changes in blood pressure were greater in subjects 80 years or older than in younger participants.
Participants' blood pressure was measured at the beginning of the study (starting in 1999) and again about two years later. Outdoor temperatures on the day of measurement were obtained from local meteorological offices. Participants in the Three-City study were from Bordeaux, Dijon and Montpellier.
"Although our study does not demonstrate a causal link between blood pressure and external temperature, the observed relationship nevertheless has potentially important consequences for blood pressure management in the elderly," the authors state. "Because the risk of stroke or aneurysmal rupture is
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European Society of Cardiology