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The researchers from the National Institute of
Health and Medical Research in Paris say four decades of
research has shown that blood pressure changes with the seasons,
but very little has looked specifically at old people.
According to Dr. Annick Alperovitch and
colleagues, even though their 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.
Billions of adults around the world suffer
from hypertension which increases a person's risk for stroke,
heart failure, heart attack and kidney failure.
For their study the French team looked at the
relationship between blood pressure and temperature in more than
8,800 men and women aged 65 or older from three French cities -
they had their blood pressure measured at regular intervals in
1999 and again two years later - outdoor temperatures on the day
of measurement were obtained from local meteorological offices.
The researchers found that both systolic and
diastolic blood pressures differed across the four seasons and
during varying outdoor temperatures and high blood pressure was
detected in about a third of the volunteers during winter and a
quarter in summer.
High blood pressure is defined as a systolic
reading of 160 or higher or a diastolic reading above 95.
The researchers say on average, each person's
blood pressure fell between the initial and follow-up
measurements and the decrease was strongly linked to outdoor
temperature, with the average systolic blood pressure 5
millimetres higher in winter than in summer.
These differences over time were larger in
participants age 80 and older.
The researchers say the higher the
temperature, the greater the decrease in blood pressure and they
suspect the reason for this might be a hormone linked to stress
that is released in cold weather possibly raises blood pressure
by speeding up the heart rate and decreasing the responsiveness
of blood vessels.
The team say elderly people may be
particularly susceptible to temperature-related variations in
blood pressure and they suggest that doctors should consider a
closer monitoring of elderly patients on high blood pressure
medicine when the temperature falls.
They say their study may help explain
well-established seasonal variations in illness and death from
stroke, aneurysm ruptures and other vascular diseases.
The research is published in the current issue
of the
Archives of Internal Medicine. |
