Right Advice, Wrong Time

The Joint National Conference on Blood Pressure, a group backed by the National Institutes of Health, has just announced that 45 million Americans are at much greater health risk than they thought. With systolic blood pressure of 120 to 139 systolic (top number), and diastolic of 80 to 89 (diastolic or lower number), tens of millions of Americans are now said to be suffering from “prehypertension”, blood pressures that may precipitate higher rates of heart attack and stroke. By failing to acknowledge that blood pressure is a “moving target” which varies approximately 20 percent during the daytime when it is usually measured, the new guidelines will frighten and confuse millions.

Blood pressure changes for many reasons, and it changes a lot. Right arm blood pressures are higher than left arm (in right handers); sitting blood pressure is different from standing blood pressure; blood pressure taken by a friend or family will be different than that taken by a doctor (white coat syndrome). Most importantly, blood pressure changes with time of day.

The changes are considerable. A person walking into a doctor’s office at 9 A.M. who has a normal blood pressure of 120/70 may find his or her blood pressure in the same office is 140/85 at 5 P.M. This is normal variation, what you should expect most days of your working life.

According to the guidelines your morning blood pressure is no problem. Your afternoon blood pressure may require you to be placed on two different anti-hypertensive drugs, perhaps for life.

What is the correct number? When is the right time to take blood pressure? The guidelines don’t say.

The new national blood pressure guidelines do point out that blood pressure be measured with a well calibrated blood pressure cuff, the cuff large enough, the arm at heart level, the patient seated and calm for five minutes, and the measurement checked at least twice.

When is the last time that happened in your doctor’s office?
The new guidelines give the right advice — Americans need to exercise more (a quarter of us do nothing), quit smoking, and eat more vegetables and fruits. But by refusing to recognize the importance of time in measuring blood pressure, they will scare many and confuse most, including doctors, and cause underdiagnosis.

Blood pressure is extremely important. But it has to be measured accurately to be meaningful. Accurate measurement requires:

Multiple measurements at the same time of day
The same conditions for measurement each time, including using the same arm
Three or more measurements on different days
Relatively relaxed clients and blood pressure takers who are not rushed.

Every part of our biology changes with time of day. Blood pressure is one element among hundreds. Your temperature will often increase 1.5 degrees to 2 degrees from morning to evening (think about that when you go through a SARS temperature screen at the airport). Weight may go up or down three pounds in a day with no meaningful change in dry weight. Aspirin will have far more gastric side effects in the morning than at night. Alcohol will have two to three times the effect at midnight than at 6 P.M.

Timing in medicine is important, for both diagnosis and treatment. If we are to protect the public health, it’s more important than ever.

Understanding your blood pressure for diabetes

Myth “You know if you have high blood pressure because it gives you headaches”

Truth High blood pressure does not always give you symptoms, and it is often found by chance during routine health checkups. Having your blood pressure checked at your annual diabetes reviews, and more frequently if your health professional suggest it, will be a more reliable indicator of whether your blood pressure is high.

My doctor tested me for Type 2 diabetes because I am having treatment for high blood pressure. Why is that?

Type 2 diabetes and high blood pressure are both linked to insulin resistance, so if you have one of these conditions it is common to have the other, too. If you keep both your blood pressure and your blood glucose level under control, your chances of developing long-term complications, especially heart disease, are greatly reduced.

What is high blood pressure?

If your larger blood vessels become more rigid and your smaller blood vessels start to constrict, your blood has to flow through a narrower space than before. The result is greater pressure on your blood vessel walls, which is known as high blood pressure or, medically, as hypertension. Having high blood pressure is common when you have Type 2 diabetes.

I have high blood pressure but I don’t feel sick. Why does it need to be treated?

Having high blood pressure makes you much more prone to cardiovascular disease (CVD) – a serious condition that develops over many years as your blood vessels gradually become narrower and less flexible. You may have high blood pressure without knowing it and, if it remains untreated, you may develop angina (severe chest pain) or have a heart attack or a stroke. Taking your blood pressure treatment as prescribed and having regular checkups can help prevent these serious conditions.

What should my blood pressure be?

If you have Type 2 diabetes your blood pressure should be below 130/80 millimeters of mercury (mmHg). In some situations, for example if you have already developed kidney damage (nephropathy), you may need to keep your blood pressure lower, for example, 125/75 millimeters of mercury (mmHg) to prevent further damage. Discussing your ideal blood pressure level, and ways to achieve it, with your health professional will give you the level that is right for you.

Why are there two figures in my blood pressure measurement?

The top figure refers to the level of pressure in your blood vessels as your heart contracts and pumps blood around your body. This is known as the systolic blood pressure. The second figure is the lowest pressure as your heart relaxes between beats. This is known as the diastolic blood pressure.

What can I do to lower my blood pressure?

Stop smoking and lose weight if you need to, eating more fresh fruit and vegetables and less saturated fat and salt (for example, less processed or commercially prepared meals) to help reduce your blood pressure. Physical activity will also lower your blood pressure. Take any blood pressure pills that you have been prescribed, even if they do not affect the way you feel, to help keep your blood pressure in the recommended range.

How low can my blood pressure go?

It would be unusual for your blood pressure to be under 100/60 mmHg if you are otherwise healthy. For every 10 mmHg drop in your systolic blood pressure (the first figure) toward this level, you benefit by reducing your risk of heart attack or stroke.

Breastfeeding’s Impact on Blood Pressure

Previous research shows women who breastfeed are more likely to have children with low blood pressure. However, a new study suggests breastfeeding’s effect on blood pressure may not be as significant as previously thought.

Researchers from London reviewed 24 studies to determine whether children of mothers who breastfeed are more likely to have lower blood pressure at different ages throughout childhood than children of mothers who do not breastfeed.

Results of the study show systolic blood pressure was slightly lower in breastfed children than in bottle-fed children. However, researchers found no significant difference in diastolic blood pressure between breastfed and bottle-fed groups. In addition, they found no specific trend among the different age groups studied.

Researchers also say most studies that show a strong correlation between breastfeeding and low blood pressure are small, which raises the possibility of publication bias. Authors of the study write, “Our systematic review found that publication bias may partly explain the lower mean systolic blood pressure observed in participants that had been breastfed in infancy, with large studies showing little difference.” Researchers add, even if publication bias did occur, the overall difference in systolic blood pressure was only 1.1 millimeters of mercury, which they say is fairly modest.

However, researchers still recommend that mothers breastfeed their infants because of other long-term benefits such as improved neural and psychological development, potential protection against obesity, and possible allergy immunity. Authors of the study conclude, “Our analysis suggests that any effect of breastfeeding on blood pressure is modest and of limited clinical or public health importance. However, blood pressure is not the only relevant outcome; the case for breastfeeding rests on a combination of short- and long-term benefits.”

SOURCE: British Medical Journal, 2003;327:1189-1192