Doctors View Early Morning Rise of Blood Pressure as `Clinically Significant'

Background

Circadian variation is the medical term for the body's natural 24-hour clock. The new science of treating certain diseases that follow these circadian patterns is known as "chronotherapeutics" and is showing success in the management of certain conditions, including arthritis, asthma, cardiovascular disease and cancer.

Clinical studies in chronobiology have demonstrated that the human body's circadian variations have certain highs and lows over a 24-hour period. Blood pressure and heart rate-physiological processes that affect vital cardiovascular functions-vary predictably over 24 hours according to this rhythm.

For Canadians keeping typical sleep-at-night/work-during-the-day schedules, most incidents of angina, stroke, and heart attack, typically occur during the early morning hours. Recent clinical studies have demonstrated that the greatest increase in blood pressure and heart rate occur just before waking, typically during the 6:00 a.m. to 12 noon period.

A survey of 300 Canadian general and family practitioners conducted between March 20th and March 27th, 1998 by the Angus Reid Group yielded the following insights,

• Four in five (79%) general and family practitioners agree that the early morning rise of a patient's blood pressure is clinically significant.
• Three-quarters indicate that the patterns of the body's natural clock are important to the diagnosis of cardiovascular disease (73%) and hypertension (77%).
• Patterns associated with the body's natural clock are also deemed important to the treatment of hypertension (84%) and various cardiovascular diseases: myocardial infarction (81%); silent ischemic events (79%); and angina (76%).
• Doctors are split on whether the profession has a good understanding of chronobiology - a science devoted to understanding how certain ailments are affected by the body's natural clock (52% indicate that they do while 48% believe they do not).
• Ninety-six percent (96%) of general practitioners and family doctors indicate that they would benefit from more information about treating people based on the body's natural clock.
• Ninety-four percent (94%) indicate that it would be beneficial to have medication that corresponds to those times when one's likelihood of having an angina attack or hypertension are highest.

Four in five doctors agree that the early morning rise of a patient's blood pressure is clinically significant. They also recognize a link between the body's natural clock and cardiovascular diseases and hypertension

Four out of five (79%) general and family practitioners agree that the early morning rise of a patient's blood pressure is clinically significant. However there is some dissonance between those who believe that blood pressure is at its highest between 7:00 a.m. and 3:00 p.m. (41%) and those who believe it is highest between 3:00 p.m. and 11:00 p.m. (40%).

In terms of angina, the plurality (43%) indicates that symptoms of angina are most likely to occur between 7:00 a.m. and 3:00 p.m. The majority believes that the symptoms of myocardial infarction and silent ischemic events (53% each) are most likely to occur between 11:00 p.m. and 7:00 a.m.

In addition, three-quarters feel that circadian rhythms are important to the diagnosis of cardiovascular disease (73%) and hypertension (77%).

A majority also agrees that circadian rhythms are important to the treatment of hypertension (84%) and cardiovascular disease, specifically myocardial infarction (81%), silent ischemic events (79%), and angina (76%).

Nine in ten physicians agreed that circadian rhythms have an influence on hypertension (90%), ischemic heart disease (91%) and angina (87%). Over three quarters (78%) feel that there is a connection to all three.

Doctors split on whether the profession has a good understanding of chronobiology - a science devoted to understanding how certain ailments are affected by the body's natural clock

While doctors indicate that they recognize patterns of the body's natural clock and certain ailments, they are basically split on whether the profession has a good overall understanding of chronobiology (52% believe that general practitioners have an overall good understanding of circadian rhythms while 45% do not). Two thirds (67%) claim to be at least somewhat familiar with the concept themselves.

General and family practitioners obtain most of their current information about chronobiology through journal articles (64%), medical education symposia (33%), and medical school (31%).

Doctors indicate they would benefit from more information about treating people based on the body's natural clock

Almost all (96%) agreed that they would benefit from learning more about circadian rhythms and the role of chronotherapy in cardiovascular disease. The principal sources of information which physicians would use to learn more about circadian rhythm and the role of chronotherapy would be medical education symposia and journal articles.

On average, physicians estimate that only a small proportion of their patients (14%) understand the concept of chronobiology. Most (86%) feel that patients should be educated about the connection between circadian rhythms and cardiovascular disease, but mainly through direct communication with their doctor.

High demand for medicine that corresponds to those times when one's likelihood of having an angina attack or hypertension are highest

General and family practitioners almost unanimously (94%) indicate that it would be beneficial for them to have medicine available that is delivered at the times of day when it is needed most for hypertension; the same (93%) was said for angina.

Almost all (93%) agreed that they would like to have treatments for cardiovascular disease available that would match a patient's circadian rhythms.

This Searle Canada/Canadian Hypertension Society/Angus Reid Poll was conducted by telephone with a random sample of 300 general and family practitioners between March 20 and 27, 1998.

These data were statistically weighted to ensure the sample's regional composition reflects that of the actual Canadian universe of general and family practitioners according to the Southam/Canadian Medical Association Masterfile, a database of all physicians in Canada.

With a Canada-wide sample of 300 one can say with 95 percent certainty that the results are within ±5.6 percentage points of what they would have been had the entire Canadian population of general and family practitioners been polled. The margin of error will be larger within regions and for other subgroupings of the survey population.

For more information on this news release, please contact:

Scott Megginson
The Angus Reid Group
Toronto, Ontario
(416) 324-2900