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BLOOD PRESSURE and CARDIOVASCULAR DISEASE
About Blood Pressure: No medical test is measured as often as Blood Pressure. The cuff is strapped on during nearly every visit to the doctor. High levels of blood pressure have been related to untimely risk of death with highest significance since before the 1930’s. Although treatment for high blood pressure is a role of the doctor, every health-interested person should understand what values of blood pressure mean and what they personally can do to reduce its risk. Blood pressure is included extensively as an important risk factor in the Life Ahead Program.
Blood pressure is a pressure on the heart measured in millimeters of mercury as the higher Systolic Pressure (BPS) during its pumping stroke, and the lower Diastolic Pressure (BPD) at the return. Values of BPS/BPD for good health that are expressed as a pair of numbers are about 120/75 at all ages. People in undeveloped areas that had lots of exercise and low cholesterol diets often maintained values at this level for life. But in our industrialized societies blood pressures usually rise with age as arteries become narrowed and stiffened with deposits. The blood pressures of the average US population used the basis for Life Ahead risks are derived from results published by the NIH as:
Age 20 30 40 50 60 70 80
Systolic (BPS) 122 125 130 135 140 146 150
Diastolic (BPD 73 75 77 79 82 84 86
The Risks: The risk of cardiovascular disease and death from all causes increases steadily with any increase in blood pressure above the above 120 systolic or 75 diastolic level. The Society of Actuaries of the insurance companies has been publishing major studies that show this since 1939. But doctors usually do not show concern and initiate corrective medication until blood pressures increase above 140/90 or a first level called hypertension. As per the above table, many US people tend to become hypertensive as move above age 60. But everyone should understand that an increase in risk is shown for any level above the 120/75 base, and an action that reduces blood pressure above this level should improve health outlook even if this is not in the higher range called hypertensive.
Their was much publicity during 2003 about the rediscovered fact - cited as new - that blood pressures above 120/75 and well below the usual guide of 140/90 could have a quite significant increase in risk of disease and death. This is a sad reflection of how little attention can be paid to and how fast so-called experts can forget long available health research. This fact was obvious from the first major study of blood pressure conducted more than 60 years ago and has been reconfirmed massively at intervals since then. Thus the risks of mildly elevated blood pressures hardly are new! The risks of blood pressures of all levels above and even below 120/75 are correctly represented in Life Ahead. The problem is there is a level at which it becomes realistic for doctors to treat blood pressures with medication. And this is a quite different level than those health-interested persons should become concerned about.
The results of two major studies were combined in developing the basic risks related to blood pressure used in Life Ahead. These were first, the very large MRFIT study (Neaton, Arch Intern Med 1992, 152:56) that related death from Coronary Heart Disease to blood pressures on 316,000 men. And second, the Pooling Study (Am Heart Assn Monograph #60) of the combined results from the Framingham and 4 other large classic US studies of coronary disease. Results of hundreds of other studies involving blood pressure probably will add little to the risks identified in these two key studies. Life Ahead relates risks to the elevation in blood pressures above selected low values of 100/60 that should correspond to nil risk of blood pressure. Values below these levels can suggest other health problems. Examples of the formulas developed are appended.
Age 20 30 40 50 60 70 80
Typical US BPS/BPD 122/73 125/75 130/77 135/79 140/82 146/84 150/86
Risk Ratio, Coronary disease 0.99 1.06 1.16 1.27 1.42 1.57 1.70
Risk Ratio, Stroke 0.98 1.08 1.23 1.40 1.63 1.88 2.10
This shows that the usual increase in blood pressure that takes place with age produces substantially increased risks of both heart attacks and strokes. At higher blood pressures of 160/90 and 170/100 risks move up to 2.04 and 2.72 times for coronary disease and to 2.71 and 4.0 times respectively for stroke. And risks that would not motivate a doctor to prescribe medication still could increase risks of major cardiovascular diseases by up to 50%.
There has been much argument about which is more important, the BPS or BPD value. Years ago most professionals felt the BPD value was most important. Some now feel that the BPS is the most important. But a balance of evidence today suggests that the BPD and BPS values are near equal in importance. Life Ahead computes separate risks for BPS and BPD and combines these into an average value. As for all other factors, the program also computes each risk as a percentage of the risk of the average US population in deriving likely rates of disease and death.
The major data on blood pressure and risk was obtained only on men. The more limited research on women shows effects similar to those for men. Two studies confirm that the effect of blood pressure on stroke was near identical for men and women (Hart, CL, Stroke 199, 30:1999) and (Ellekjaer, I, Blood Press 2001, 10:156). Other studies suggest the risk of elevated blood pressure on coronary disease for women is at least equal to and may exceed that for men.
Measuring Blood Pressure is a Problem: A problem with blood pressure is that values can fluctuate quite a bit during a day and over time. Many people suffer what is called “White coat hypertension” because pressures can go up due to mild nervousness in the presence of the nurse or doctor. Values also can go up after a heavy meal or some mental stress. Health-interested persons should consider buying a measurement kit – they are not expensive – and learn how to take their own blood pressure when calm and undisturbed as in the morning before breakfast. Note again that a value such as 140/82 that usually would not lead a doctor to provide blood pressure medication still produces substantial risk elevations of 1.42 and 1.63 in heart disease and stroke. This is a risk that must be offset by good health habits.
Keeping Blood Pressures Down: Blood pressures increase with age during life mostly because of the gradual formation of atherosclerosis that narrows and stiffens arteries. Thus long term attention to diets moderate and low in cholesterol may be a most important long term action that can control blood pressures. But once pressures become elevated they are not likely to drop very quickly in response to a change in cholesterol. There is much health advice being given today on “How to get your blood pressures down." The actual research shows that reducing blood pressure very much by other than medication is not easy.
Salt and Sodium has been regarded as a BIG villain in causing high blood pressure. Extensive research from more than a hundred studies (See the section on Sodium, Salt and Blood Pressure) now shows that the true role of salt in causing blood pressure has been vastly overrated. A substantial reduction is dietary sodium is unlikely to lower blood pressures by more than 4/2 mm of BPS/BPD for a hypertensive person and a practical lowering of sodium via diet usually will contribute a reduction in BPS/BPD of perhaps 2/1 mm for an average person. This later change means that it may take a very large reduction in dietary salt to reduce blood pressure say from 140/85 to 138/84. See more about this in the paragraph on diet that follows.
Exercise and Fitness will offer some help in lowering blood pressure. A review of the results from 8 studies in which substantial amounts of exercise and large differences in levels of fitness were achieved suggests that reductions of 7/4 mm of BPS/BPD were obtained. Exercise of hypertensive men achieved a reduction of 12/7 mm. in one study. But these reductions probably are larger than most people are likely to achieve from their exercise programs.
Blood Pressure clearly is related to body weight. The averaged result from 6 studies reviewed for Life Ahead found an average change in blood pressure of 1.04/0.75 for each change of 1 in BMI. Thus a drop of 5 in BMI or about 30 pounds in weight would reduce blood pressure by 5.1/3.75 mm of BPS/BPD. This is a quite useful change.
Increased Potassium Intake can reduce blood pressure significantly. A Meta Analysis of 19 clinical trials (Cappuccio, J Hypertens 1991, 9:465) found that ‘Potassium Supplementation’ reduced average blood pressures of BPS/BPD by 5.9/3.4 units. It can be far more useful to improve potassium by diet than by supplements. A typical potassium supplement is only 100 mg. But a single half melon or baked potato can add 500-700 mg of potassium from diet. (See the ‘Sort Diet’ option in Life Ahead to view potassium values of various foods.). Potassium is included as a separate risk in Life Ahead that includes its risk on stroke. Increased Calcium intake also can improve blood pressures slightly. A meta study of 33 clinical trials found that ‘supplementation’ with calcium reduced blood pressures by a small 1.27/0.24 mm of BPS/BPD.
Diet and Blood Pressure: There has been much publicity recently on the success of the so-called DASH diet in reducing blood pressure. This diet proposes most of the today’s major diet advice for health as: 7-8 daily servings of grain and grain products; 4-5 servings of vegetables; 4-5 servings of fruits; 2-3 servings of low-fat or nonfat dairy products; 2 or fewer servings of meat, poultry; 4-5 servings of nuts, seeds and legumes (per week); and limited intake of fats and sweets.
Three levels of sodium, 1500, 2300 and 3300 in diet were tested for 30 days on two groups of about 200 people, with one group using an average diet and the second using a DASH diet. For sodium the usual diet group obtained a reduction in BPS/BPD of 6.7/2.3 mm for the change from 3300 to 1500 in sodium, but the DASH diet group obtained a change of only 3.0/1.5 over same large range. More interesting was the average improvement of 5.0/2.5 mm. in BPS/BPD for using the DASH vs. the conventional diet. This improvement as per the above table would reduce risk of coronary disease by about 10%, a small but useful benefit.
The reduction of 3/1.5 mm obtained for sodium reduction found for the DASH diet is similar to that found from the average of 58 studies of salt. The higher reduction obtained with usual diet is not an unusual result, as some of the 58 other studies found reductions in this range. These are quite small differences that are difficult to measure accurately and that would have a minimal effect of risk of disease. Another possible reason for the variable results on blood pressure and sodium from different studies may be that it is impossible to change one nutrient in a diet without changing a number of other nutrients at the same time. Were the diet differences in these studies only for sodium, or did other nutrients that changed with addition of high salt high contribute to the various observed results?
Seven different specific suggested diets given in the NIH’s free publication on the DASH diet were analyzed via the Life Ahead method that values up to 20 different included nutrients in each food. The average of these seven DASH examples tested as expected with higher Well-Days than a US average. But the health values of the individual daily DASH diets suggested varied by up to 1,500 Well-Days – or by 4 years of likely healthy life. The effect of the diets on blood pressure suggest differences of a maximum of only 250 Well-Days. Two of the seven individual daily DASH diets that attempted to meet the above diet objectives were valued via Life Ahead as not very healthy. A problem is that changing foods in diets to achieve one objective can change other factors that cause an opposing net result. This same problem was found when valuing differing daily diets recommended Atkins and Pritikin. Different specific diets recommended from each author varied substantially in their estimated health benefit. It is not the “Name” or “Type” of the diet that counts. It is the actual individual values of foods that each includes.
Mechanisms via Blood Pressure: How does elevated blood pressure increase risk of cardiovascular diseases? It is likely that increased blood pressure is not a direct cause of most diseases involved, but rather is an indicator that points usefully to their health risk. Strokes that involve bursting of small blood vessels in the brain are clearly related to blood pressure, but most strokes are ischemic or related to atherosclerosis that blocks arteries. As arteries gradually stiffen and clog during life from the atherosclerosis that produces cardiovascular disease blood pressures tend to rise. Some research does suggest that higher blood pressures may increase the rate of atherosclerosis somewhat. But blood pressure medications can produce their benefit rather quickly without changing atherosclerosis, and probably benefit via different biochemical mechanisms. The Life Ahead formulas now provide only statistical relationships of blood pressure to disease, and a better Global understanding of how blood pressure produces risks is needed.
Keeping Blood Pressures Down: Health habits clearly can help keep blood pressures lower. Although none of the above factors produces more than small changes in blood pressures for practical changes in usual habits, a combination of habit changes can contribute usefully. Exercise and fitness probably can help most. Including more diet potassium appears to be another key factor that can benefit, and those overweight should be helped by weight reduction. A little benefit may accrue to some that now have fairly high sodium by sodium reduction, and more gain from diet probably can be derived by general modification of diet toward the desirable goals noted for the DASH diet.
Life Ahead compares levels of every included factor with best values for health in every computation. Thus if habits produce desired health factor levels, they also should produce a near maximum benefit in controlling blood pressures.
Medication: Blood pressures become a recognized medical risk problem when they move much above 140/85, and then to 150/100 or higher. At such levels it becomes evident that a practical change in lifestyle habits will not succeed in reducing pressures adequately. Blood pressure medications have been very successful in controlling blood pressures of most people. Use of medication does not eliminate the need for good lifestyle habits because good diet and exercise can help further. But it is not sensible for anyone to avoid medical help when this becomes needed. Life Ahead is designed help individuals protect their health, and attempts not to enter into the medical area of treatment that needs the expertise of the professional doctor. The doctor can help many of us improve future health by selecting and prescribing appropriate blood pressure medications.
Blood Pressure Valuation and Risk in Life Ahead: Life Ahead develops lifetime average population profiles of blood pressure by each year of age for men and women as per the above table of example values vs. age. This profile then is then modified from entered blood pressure values at either present age or age at first use of medication. If these entered pressures are higher or lower than profile at age, the prior profile is adjusted upward or downward stepwise from youth to this present value. This in effect assumes a progression of blood pressure with age that moves gradually from youth to the first entered value. If blood pressure medication is started at an age, the profile is then adjusted downward to the new value achieved at this age, and stays at that value until modified again by a later entry of blood pressure.
Life Ahead identifies risks of most factors as diet and exercise as all inclusive. That is, these factor risks automatically include any risk due to an associated change in blood pressure. The ‘Good Habits’ valuation assumes further that if the total of BPS and BPD exceed 230 (ie 140/90) and that blood pressure medication is not being used, that such medication probably should be considered and that the individual should be consulting a doctor. It then assumes that medication will be used and that this will improve blood pressures to 135/80. If medication is used, the actual blood pressures obtained should be entered into the program at age medication is first used. This new entered value will be used from this date thereafter. Thus if medication is used, it is important to enter blood pressure prior to the use of medication.
Life Ahead computes the risk ratios related to blood pressure for each cardiovascular disease from differences in actual blood pressure from the above average population age-profiles of pressures at each age of life, and uses these risks together with risks from other factors to compute a likely annual incidence of each disease and death from disease included.
Formulas used in Life Ahead:
For Risk of Coronary Disease vs
BPS Risk Ratio = exp ( -0.452 + 0.0226 * (BPS -100))
BPD Risk Ratio = exp ( -0.522 + 0.0348 * (BPD - 60))
Risks of Stroke are at a somewhat higher level than these risks for coronary disease.