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Friday, January 20, 2012

Who Knows What Their Blood Pressure Is?



     Everyone knows that blood pressure is one of the most important variables in health. Uncontrolled blood pressure leads over many years to strokes, heart attacks, peripheral vascular disease, aneurysms, and heart failure. 
     Most people know that the recommended level of blood pressure is to have the upper number (systolic pressure) be less than 140 mm Hg, and to have the lower number (diastolic pressure) less than 90 mm Hg.  The systolic number is the level of pressure achieved in the arteries when the heart contracts, and the diastolic number is the level of pressure in the arteries when the heart relaxes in between beats. Of these two numbers the upper systolic pressure number is the more important.
     So, what's your blood pressure? How would one know? Most people know (if they can remember it) their blood pressure from a visit to the doctor's office. But is the number you get from the doctor's office the correct number? A large number of new studies suggests that it is not. 
     First, there is the factor of "white coat hypertension," which by now most of my patients seem to know about; this is when your blood pressure is transiently elevated because one may feel somewhat nervous or anxious about going to the doctor. Pain is another factor that will elevate the blood pressure in a doctor's office. 
     A second factor is that in the busy flow of doctors' office practice, the correct technique for measurement may not be employed. According to the experts, the proper way of measuring blood pressure is to check it after at least 5 minutes of quiet sitting waiting for the doctor. In most practices, the nurse checks it as soon as or right before leading a patient into the exam room, which is not optimal. Usual practice, however, is for the doctor to re-measure any high readings after 5 minutes has passed. If the patient has been waiting for 45 minutes to an hour for the doctor, however, the blood pressure may be elevated just due to aggravation.
     The expert recommendations also call for the blood pressure to be taken while the patient is sitting upright in a chair with his/her back supported and the feet flat on the floor. Checking the patients' blood pressure while they are sitting on the exam table with their backs unsupported and their feet dangling in the air is not consistent with these standards, but it is, in fact, the most common way blood pressure is measured in the office. 
     Other problems that occur in doctors' office are the use of an incorrect cuff size (cuffs that are too small tend to elevated the pressure readings) due to an inexperienced staff person. Also, the blood pressure devices themselves can get banged up, dropped, or just old and no longer give accurate readings.
     For all of these reasons and some others a single blood pressure measurement in a doctor's office is simply not a reliable indicator of the true blood pressure.  A new study in the Annals of Internal Medicine* concludes that: "Physicians who want to have 80% or more certainty that they are correctly classifying patients' BP control should use the average of several measurements. Hypertension quality metrics based on a single clinic measurement potentially misclassify a large proportion of patients." The data from this study show clearly that patients could not be classified as having BP that was in or out of control with 80% certainty on the basis of a single clinic systolic blood pressure measurement anywhere in the range from 120 mm Hg to 157 mm Hg. The investigators recommend obtaining an average of several measurements and feel that the optimal number of readings to average is 5 to 6.
     Based on several other studies it now appears that the optimal way to measure and manage patients' blood pressure is for the patients to monitor their blood pressure at home with the increasingly accurate and inexpensive automatic measuring devices that are now available. This is actually better than using the numbers obtained in the doctor's office, even if the doctor does go through the trouble to average 5-6 readings. (Most don't!)
     I advise patients not to be obsessive about it. (This tends to raise your blood pressure.) There is no point in checking it several times a day; nor is there any need really to check it more than twice a week. I tell most patients that once a week is fine. Ideal management calls for patients to bring into their doctor a list or log of at least 5-6 recent measurements so that a reliable average blood pressure may be obtained. In the near future, I expect that the makers of the blood pressure devices will computerize and memorize hundreds of measurements so that a continuous average is reported automatically. Until then we'll just have to obtain an average the old fashioned way--add up all the numbers and divide by the number of readings. The improvement that should come soon to doctors' offices is that electronic medical record system will begin to automatically calculate the average of multiple physician readings.
     It is certainly clear to me in my practice that blood pressures vary quite erratically for many patients, and I only make my decisions on blood pressure medication adjustment based on an average blood pressure. I recommend that all patients who have been told that they have high blood pressure get themselves a home blood pressure measuring device (now available for less than $50). If they can bring in at least 5-6 readings from home every 4 months we will really be able to do a great job of managing hypertension.

* References: (Powers BJ et al, "Measuring blood pressure for decision making and quality reporting: Where and how many measures?" 2011; 154: 781-788; editorial by Appel LJ et al., "Improving the measurement of flood pressure: Is it time for regulated standards?" 154: 836-7) 

Thursday, January 19, 2012




     It is a long-standing problem that there has been little or no hard evidence to guide the decision on how to screen for and prevent osteoporosis. The United States Preventive Services Task Force has gone ahead and endorsed it despite the lack of evidence. The recent "Welcome to Medicare" guidelines will pay for it every 2 years. I have long been opposed to this test because it is expensive and because no one is sure how to use it. The vast majority of its value lies in the first screening with a bone density test technique, and, simply stated, none of the numerous experts has any real idea of if and when to repeat the test for patients who are normal, for patients who have osteopenia, and/or for patients who have actual osteoporosis.  My recommendation has been for everyone simply to exercise regularly and take the recommended amount of daily calcium (1000 mg/day) and vitamin D (800 IU/day).
     Until now, that is. A study just published today in the New England Journal of Medicine (Gourlay ML et al. NEJM 2012; 366: 225-33) answered the question. They studied a group of 4957 women, 67 years of age or older, who had normal initial bone density or had only mild osteopenia on initial testing; these women had no history of fracture of the wrist, hip, or spine and were not taking medications like Fosamax for osteoporosis. They analyzed their bone density at 2 years, 6 years, 8 years, 10 years, and 16 years. They divided their subjects into 3 subgroups:  a group with normal bone density and a group with osteopenia (mild, moderate, and severe) and analyzed the time until progression to frank osteoporosis. 
     The estimated time for women with normal bone density to progress to osteoporosis was 16.8 years. The estimated time for women with mild osteopenia to progress to osteoporosis was 17.3 years, for women with moderate osteopenia, 4.7 years; and for women with severe osteopenia, 1.1 years.
     The investigators conclude that the appropriate re-screening interval in which to repeat any type of bone density testing was 15 years for either normal women or women with mild osteopenia. For women with moderate osteopenia, rescreening should take place in 5 years, and for women with advanced osteopenia, rescreening should take place every years.
     This recommendation is clear and firmly evidence-based. A majority of the currently carried out rescreening with bone density tests, usually on an annual or biannual basis, should cease. Live a healthy lifestyle, exercise, take your calcium and vitamin D, and say your prayers--"Lord, may I live another 15 years."  Then you can get your repeat bone density test and derive some benefit from it. The rest is waste for women with normal bone density or only mild osteopenia.