The Seasonality of Hypertension: A Reason to Have a Home Blood Pressure Monitor
December 18, 2013
Written by: Victor E. Battles, M.D.
Because of the seasonality of hypertension or the tendency for significant BP changes to occur with changes in
seasons, it is wise to own and make frequent use of a home blood pressure monitor. Seasonal variations in BP have
been recognized and well documented in several research studies from the early 1980s through the late 1990s, but
optimal use of the information derived from those studies cannot be achieved without the widespread use of home
blood pressure monitor devices. By being aware of the seasonal changes in patients affected by this phenomenon
doctors can make the appropriate adjustments to achieve and/or maintain good BP control and minimize the damaging
effects of high blood pressure on various parts of the body.
Research studies have shown an inverse relationship between environmental temperature and BP levels, with
pressure readings being higher during cold weather and lower in warm and hot weather. A notable French study
involved 8,801 adult patients greater than 65 years of age over a two-year period of time, during which time
33.4% of the individuals in the study had high BP readings during the winter compared to 23.8% during the
summer. The elevated blood pressure readings during the winter were seen for both systolic and diastolic
pressures but the study only reported the average systolic pressure elevation for the group, which was 5 points
higher in the winter than in the summer.
Other studies performed using home blood pressure monitor technology or 24 hour ambulatory monitors have shown
similar findings, with the most drastic variations in BP occurring in regions of the world with the most
extreme seasonal changes in the temperature. The BP changes that occurred were similar between men and women
The cause of this phenomenon, known in the health-care community as the seasonality of hypertension, is
unknown, but a few theories have been proposed. One is that the sympathetic nervous system, which prepares the
body to deal with stressful or emergency situations, is ramped up by cold weather which, in conjunction with
decreased sodium excretion due to diminished sweating causes the BP to rise. The corollary hypothesis is that
during warm and hot seasons larger amounts of sodium are excreted through sweating. The increased sodium
excretion is accompanied by loss of fluid volume in the blood vessels, thereby reducing blood pressure.
Some have even postulated that high blood pressure readings during the winter may be responsible for the
increased occurrence of stroke and cardiovascular complications such as heart attack, congestive heart failure
and angina during the winter months, which have been observed in some studies. Those that know or knew someone
who suffered a heart attack or stroke while shoveling snow would have no difficulty placing credence in this
theory, particularly if the victim had hypertension which was not being closely monitored between season
Not only is close blood pressure tracking via the use of a home blood pressure monitor important during the
cold seasons, but is also important as the weather warms and becomes hot, particularly if an individual with
hypertension is taking a diuretic (a medication which increases urination and sodium excretion). Since
diuretics not only cause a desired drop in blood pressure, if the sodium excretion caused by them is excessive
they can cause abnormally low blood pressure readings, which in and of themselves can be problematic,
particularly in the elderly where the risk of fainting and bodily injury are commonplace.
The season to acquire a home blood pressure monitor, if one is not already possessed, is therefore not just
during the winter, but during any season of the year, with frequent and regular use of it and reporting of the
blood pressure results to your physician. It is an ideal opportunity for patient engagement in blood pressure
management, which increases the likelihood of quality improvement in health care and reduced health-care
Victor E. Battles, M.D. is a board-certified internist with 30 + years of patient contact. Dr. Battles has
been a principal investigator in several hypertension clinical research trials, and is the founder of
Proactive Health Outlet.
Get a home blood pressure monitor