Optimal Blood Pressure

Years ago doctors believed that a systolic blood pressure of 100 plus your age was perfectly acceptable and it was physiologically normal for blood pressure (BP) to rise with age. This belief ended when it became clear that a 65-year-old person with a BP of 160/85 was at a much greater risk of cardiovascular disease than someone the same age with a much lower BP. High blood pressure, or hypertension, was then defined as a BP of 150/100 or higher regardless of age. As more data became available it became clear that even this method for diagnosing hypertension was still associated with much greater incident of cardiovascular disease.

Currently, high blood pressure or hypertension is defined as 140/90 or higher. However, the newest guidelines for those at very high risk for cardiovascular disease, such as those with diabetes or a previous heart attack, call for treatment beginning when BP is 130/85 or higher. It is now clear that a BP considerably less than 130/85 is usually better for preventing death from cardiovascular disease.An optimal BP would be one that is associated with the lowest overall risk of dying. A recent publication1 used an analysis of 61 prospective studies to examine the relationship between one’s BP and risk of dying. They looked at the impact of BP at different ages to determine the BP level at which the risk of dying from a stroke, heart attack or other cardiovascular disease incident was the lowest. They also looked at the relationship between BP and the risk of dying from all causes for people in different age groups. The figure on page 29 shows the relative risk of dying from a heart attack based on blood pressure levels from low to high. It is clear that the risk of dying from a heart attack is lowest for those with the lowest BP. In fact, the risk of dying from a heart attack for people 40-49 years old doubles for every 20-point increase in systolic BP starting at 115. The risk of increasing systolic BP was somewhat less for older people, but this analysis showed that the absolute risk of dying from a higher systolic BP was much greater for people in the oldest age group. The Higher Your BP the Sooner You Are Likely to DieIt is important to note that the risk of dying of cardiovascular disease increased above systolic BP of 115 and/or a diastolic BP of 75 and this was true for all middle-aged and older adults. The authors of this massive meta-analysis conclude, “Throughout middle and old age, usual blood pressure is strongly and directly related to vascular (and overall) mortality, without any evidence of a threshold down at least to 115/75 mmHg.” Other data presented in this study made it clear that the risk of dying from a stroke increases somewhat more rapidly with rising BP than the risk of dying from a heart attack. The lower the BP, the lower the risk of any form of cardiovascular disease. This study also showed a higher BP was associated with a modest but statistically significant increased risk of death from all other causes combined.Unfortunately, data from the Framingham Heart Study recently showed that BP rises dramatically with age. This data showed that 90% of Americans eventually get diagnosed with hypertension. Most will have hypertension by the time they are in their 60s. More than 2/3 of those who make it to age 65 without hypertension will develop it before their 75th birthday. Can This Rise in BP Seen with Age Be Stopped?A diet with a lot less salt is the most important way to prevent the rise in BP seen with increasing age. There is now overwhelming scientific evidence that reducing salt intake to below 1,200 to 1,500 mg daily will probably prevent the rise in BP seen in almost all Americans as they grow older.2 In addition to salt restriction, preventing weight gain and avoiding heavy alcohol intake will also help keep BP in the ideal range (below 110/70) throughout life. Finally, a DASH-style diet that emphasizes whole grains, legumes, lots of vegetables and fruits, some nonfat dairy products and a little omega-3 rich seafood, nuts and seeds should help nearly all Americans prevent BP from rising with age. By James J. Kenney, PhD, RD, FACN. References1. Lancet 2002;360:1903-132. Kenney, JJ. Salt Toxicity - www.foodandhealth. com