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Elderly's blood pressure higher in cold weather

(Xinhua)
Updated: 2009-01-13 14:19

WASHINGTON -- Falling temperatures in winter may cause an unhealthy rise in the blood pressure of older people, according to a report in the Archives of Internal Medicine.

Previous research has demonstrated that blood pressure changes with the seasons but few studies have looked specifically at older adults, Annick Alperovitch of the National Institute of Health and Medical Research in Paris and colleagues said.

"Elderly persons may be particularly susceptible to temperature-related variations in blood pressure," they wrote in the study released Monday.

Researchers assessed the relationship between blood pressure and temperature in 8,801 individuals who were at least 65 years old from three French cities.

Their blood pressures were 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.

Both systolic (top-number) and diastolic (bottom-number) blood pressures differed across the seasons and across the distributions of outdoor temperatures, the study showed. The average systolic blood pressure was five millimeters of mercury higher in winter than in summer.

High blood pressure, defined as a systolic blood pressure of 160 millimeters of mercury or higher, or a diastolic blood pressure of 95 millimeters of mercury or higher, was detected in 33.4 percent of participants during winter and 23.8 percent during summer.

On average, each individual's blood pressure decreased between the initial and follow-up measurements. The decrease was also strongly correlated with outdoor temperature.

"The higher the temperature at follow-up compared with baseline, the greater the decrease in blood pressure," the authors wrote. The differences over time were larger in participants aged 80 and older.

The researchers said they did not know the reason for the association, but thought that the release of a hormone in response to cold might increase blood pressure by speeding the heart.

"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 wrote.

It may explain well-established seasonal variations in illness and death from stroke, aneurysm ruptures and other vascular diseases.

"Because the risk of stroke or aneurysmal rupture is highest in the elderly, improved protection against these diseases by close monitoring of blood pressure and antihypertensive medication when outdoor temperature is very low could be considered," they suggested.