Dear Dr. Roach: I have been confused about what normal blood pressure is for me (or anyone). I know there are some issues on what normal is today, but let us say that normal is 120/80 mm Hg. Does this mean that 110/90 mm Hg, 130/70 mm Hg, or 150/50 mm Hg is also normal? Is there any significance of the ratio of systolic/diastolic blood pressure?
L.P.
Because so many people have high blood pressure, and the consequences of untreated or poorly treated high blood pressure include a risk for heart attack and stroke, it’s critically important to understand this thoroughly.
For a young, healthy person, the lower the blood pressure, the lower the risk of blood vessel damage that leads to these dreaded complications of heart attack and stroke. I routinely see people with blood pressures of 90/60 mm Hg who are just fine (although they are a bit more likely to faint).
But for middle-aged and older people, we define normal blood pressure as when the systolic (first or top number) pressure is less than 120 mm Hg and the diastolic (the second or bottom number) is less than 80 mm Hg. Elevated blood pressure is when the systolic pressure is between 120-129 mm Hg and the diastolic pressure is less than 80 mm Hg. It’s considered hypertension when the systolic number is 130 mm Hg or greater, or the diastolic number is 80 mm Hg or greater. So, all of the readings you proposed are hypertension, not just elevated blood pressure.
Of course, the higher the reading (in general), the higher the risk of damage to the blood vessels, and after some years, the higher the risk of heart attack or stroke. It’s not the ratio of the systolic and diastolic numbers that is of interest; it’s the difference between them (also called the pulse pressure). So, with the numbers you gave, the pulse pressures are 20, 60 and 100. Independent of blood pressure levels, a higher pulse pressure confers additional risk to the person, mostly because very stiff blood vessels cause a high pulse pressure. Different types of blood pressure medicines affect pulse pressure differently.
Dear Dr. Roach: Is a platelet count of 135,000 low or in the normal range for a 76-year-old male in good health with no signs of abnormal bruising or bleeding?
P.R.
The normal range for a platelet count is 150,000-450,000 per microliter, so 135,000 is just below the lower limit of normal. However, it’s quite rare to have abnormal bleeding with a platelet count like this, even under stress like a surgical procedure. About 2.5% of the healthy population will have a platelet count below 150,000, so a level of 135,000 may not represent disease at all. Typically, the risk of spontaneous major bleeding becomes high when platelet levels drop below 30,000.
The most common cause of low platelets in older adults is an immune-mediated condition called “immune thrombocytopenia,” but there are many possible causes, including medications, bone marrow diseases, and liver disease. For a 76-year-old, if repeat blood counts show that the platelet count is stable in the 100,000 range, most experts would not do further testing in absence of any symptoms.
Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to [email protected]
