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Elderly
may have higher Blood Pressure in Cold
Weather
Newswise — Outdoor temperature and blood
pressure appear to be correlated in the
elderly, with higher rates of hypertension
in cooler months, according to a report in
the January 12 issue of Archives of Internal
Medicine, one of the JAMA/Archives journals.
Seasonal variations in blood pressure have
been recognized among the general population
for 40 years, according to background
information in the article.
However, few previous studies have looked
specifically at older adults.
“Elderly persons may be particularly
susceptible to temperature-related
variations in blood pressure,” the authors
write.
“The baroreflex, which is one of the
mechanisms of blood pressure regulation, is
modified in elderly subjects, and it has
been hypothesized that disorders of
baroreflex control and enhanced
vasoreactivity [sensitivity of blood
vessels] could contribute to the
aging-associated increase in cardiovascular
morbidity [illness].”
Annick Alpérovitch, M.D., of the Institut
National de la Santé et de la Récherche
Médicale, Paris, and colleagues assessed the
relationship between blood pressure and
temperature in 8,801 individuals 65 or
older.
All were part of the Three-City study,
conducted in three French metropolitan
areas.
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.
Both systolic (top-number) and diastolic
(bottom-number) blood pressures differed
across the four seasons and across the
distributions of outdoor temperatures.
Average systolic blood pressure was 5
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.
This 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
write.
These differences over time were larger in
participants age 80 and older.
“Mechanisms that could explain the
association between blood pressure and
temperature remain undetermined,” the
authors continue.
The sympathetic nervous system (which helps
control involuntary actions, such as stress
response) is activated and the hormone
catecholamine is released in response to
cold temperatures, which may increase blood
pressure by speeding the heart rate and
decreasing the responsiveness of blood
vessels, they suggest.
“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
write.
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.”
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