If you’ve been diagnosed with high blood pressure (hypertension), your doctor may have recommended that you frequently take your blood pressure at home. But they may not have known just how good that advice was. Evidence is accumulating that monitoring your blood pressure at home might save your life — especially if you’ve been diagnosed with high blood pressure (hypertension) and you’re having trouble controlling it. Ongoing, or ambulatory, blood pressure readings — especially at night — might provide a better picture of a person’s blood pressure profile — and risk of dying from heart disease or stroke — than do periodic checks in doctors’ offices.
A research team led by Gil F. Salles, M.D., Ph.D. reported those results in the November 24 issue of Archives of Internal Medicine (Arch Intern Med. 2008;168:2340-2346.) Salles and colleagues examined 556 patients with hypertension that had not responded to treatment. People in the study attended an outpatient clinic between 1999 and 2004. Researchers performed a clinical examination on each patient, then monitored their blood pressure continuously for a full 24-hour period, every 15 minutes throughout the day and every 30 minutes at night. These steps were repeated at least three to four times a year until December 2007.
After almost five years, 109 (19.6 percent) of participants had a cardiovascular event or died of cardiovascular disease. This included 44 strokes, 21 heart attacks, 10 new cases of heart failure and five sudden deaths. Seventy patients (12.6 percent) died, including 46 (8.3 percent) of cardiovascular causes.
But here’s the “news you can use” part: When blood pressure was measured in clinic, it did not predict any of these events. In contrast, people who had higher average blood pressures as measured at home (both the [systolic] and bottom [diastolic] numbers) were more likely to have experienced fatal and non-fatal heart events. This association remained after controlling for office blood pressure and other risk factors for heart disease. In addition, nighttime blood pressure was a better predictor of heart events than was daytime blood pressure.
The study has tremendous implications for addressing hypertension, which is one of the most common risk factors for heart disease and stroke. Here’s the big picture: The World Health Organization estimates that 1.2 billion people worldwide have hypertension. About one in three adults in the United States, or about 74.5 million people, have high blood pressure. According to the CDC, hypertension affects 29 percent of all adults 18 and older, and an additional 28 percent have pre-hypertension. Percentages are similar in the United Kingdom, where hypertension affects about half of people over 65 and about one in four middle-aged adults. The costs are astronomical, not only for individuals but for societies at large.
Keeping blood pressure within a normal range (with an upper limit of 120/80 mm HG) significantly reduces the risk cardiovascular events. Hypertension is preventable, and in most cases, controllable. More than 100 medications are available that can help lower blood pressure, and lifestyle interventions such as changing diet and increasing your activity level have been shown to be effective. Yet more than half of people with hypertension don’t have it controlled, and nearly a third who have it aren’t being treated for the condition. According to the American Heart Association, the death rate from high blood pressure increased 19.5 percent from 1996 to 2006, and the actual number of deaths rose 48.1 percent.
But the first challenge to controlling hypertension is getting accurate measurements, which can be tricky. Blood pressure is affected by so many variables — time of day, medications, hydration levels, anxiety, mood, activity, pain, illness — that it’s almost impossible to determine whether a reading taken in a doctor’s office is normal for that person. Plus, blood pressure readings taken in physicians’ offices may be inaccurate, not only because of anxiety due to “white coat syndrome,” but because clinical support staff — and physicians themselves — may simply not be very good at measuring blood pressures. They may be too busy, machines may not be calibrated correctly, and a host of other problems may occur.
And that’s what I find exciting about Salles’ study. It takes the the measurement out of the artificial construct of the clinicians’ office and into people’s real, day-to-day lives. The American Heart Association is , with a “call to action” to increase home blood pressure monitoring. “Given the demonstrated benefit of good blood pressure control on outcomes such as heart failure and stroke, it behooves us to make good use of opportunities such as home blood pressure monitoring, which can both improve blood pressure control and engage and empower patients to be an active part of the process.”
Radical thought. You can be an active participant in your own health care. Here’s how:
- Purchase a decent blood pressure monitor and have it calibrated regularly. Several models are available, and no one model is right for any one person. But avoid the fingertip models, which are notoriously inaccurate.
- Take your blood pressure regularly, at the same time of day. Be sure to include a night-time measurement
- Record all readings ( some machines will do this for you automatically)
- Bring your results with you when you go to the doctor’s office