Blood Pressure: How Low is Too Low?

dr_duane_graveline_m.d._134By Duane Graveline, M.D., M.P.H.

I have been increasingly skeptical of the progressive lowering of target blood pressure values as the decades have swiftly passed.

When I was in medical practice, marching lockstep with my peers and far too busy to research for myself, I had neither the time nor the inclination to question the rationale behind these progressive redefinitions of normal blood pressure. Then came retirement and the internet and abruptly I had both the time and capability to critically examine the data.

For thirty years I had been completely satisfied with a 140/90 standard as the upper limit of normal blood pressure established long before I was in training in the 1951-1955 era. Throughout my 30 years of medical practice this target served me well. With experience I confidently made small adjustments to better serve my patients.

For those over 60 years of age, I felt justified in raising the acceptable systolic standard to 150 as a general rule and giving increasing importance to the diastolic before making my decision to start blood pressure medication.

The diastolic would generally have to be 95 for me to start writing prescriptions. After all, we are talking expensive, side effect prone drugs for the rest of the patient's life - a not inconsiderable consideration.

I felt I was applying reason in my medical practice in doing so and what better person to apply reason to medicine than a thoroughly experienced family doctor? Now that my own health care is being given by much younger doctors, I am moderately shocked when they regard my present 140/90 as hypertension deserving of treatment.

First of all, I am astonished at the measurement techniques they practice. You are perched on a bench and asked to hold your arm out for application of the blood pressure cuff and throughout the measurement the nurse is questioning you about the weather, what part of the country you are from and what type of practice did you have with absolutely no awareness of the effect of my verbalization on blood pressure. In my office, blood pressures were taken with the patient reclining comfortably and their arm resting on the table.

Having spent years in exercise physiology prior to my medical practice I was familiar with the huge boost in blood pressure while talking. So lack of comfort and talking are two biases guaranteed to invalidate your blood pressure value.

One of the most surprising effects of factors that can falsely elevate a blood pressure reading is the effect of discomfort on brain function that I learned about in medical school. Using a special device capable of recording blood pressure minute by minute, our environmental physiology professor first recorded our blood pressures during one minute of immersion of one of our hands in iced water. I was not surprised to find my blood pressure peaking at 245/145.

The surprise came later when we were to learn of our blood pressure response during a relatively innocuous act. We were instructed to perform a simple mental arithmetic exercise by starting with the number 100, then in our heads, subtracting by 7 (100, 93, 86, etc.)

The whole class was amazed to see a spike in blood pressure equal to what we had recorded from the iced water test. This brought home to us the importance of both physical and mental comfort when taking a blood pressure reading. This knowledge would remain with us forever as we guided our office staffs in proper blood pressure testing techniques.

Now I find that only 120/80 will appease my doctor and any foot-dragging on my part will signal that I am going to be a terribly overbearing and non-compliant patient.

Clearly the present atmosphere among clinicians is "the lower the better" for blood pressure and I happen to know that there is not one shred of research evidence that supports this view.

You can imagine my pleasure when I read of the INVEST study (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3008373/) that showed that lower is not better, it is far worse. The INVEST study was the first to evaluate the effects of blood pressure lowering using diabetic patients who also had coronary artery disease. You don't get riskier patients than diabetics with coronary artery disease, so what is true for this class of patients will likely hold true over a much wider range of patients.

Researchers analyzed data collected from 6,400 patients from late 1997 to spring 2003. The patients, who were 50 or older, were recruited from more than 850 sites in 14 countries. Rhonda Cooper-DeHoff, Pharm.D., an associate professor of pharmacy and medicine at the University of Florida was the lead investigator of this study. She said the range considered normal for healthy Americans actually proved riskier in cardiovascular events for those with a combined diagnosis of diabetes and coronary artery disease.

A J-curve response was seen where blood pressure reduction was accompanied by a decrease in complications down to just below 140 systolic, below which a progressive rise in complications occurred peaking at the 120/80 range.

No doubt this information drew a murmur of surprised response from the medical audience and no doubt raised the ire of drug companies everywhere to learn that one of their most lucrative sources of income had just been seriously threatened.

"Our data suggest that in patients with both diabetes and coronary artery disease, there is a blood pressure threshold below which cardiovascular risk increases," Cooper-DeHoff said. She recommended raising the target systolic level above 120 for blood pressure in patients with diabetes and coronary artery disease, predicting that levels between 130 and 140 appear to be the most healthful.

My assessment of this study is that the ideal target blood pressure values for diabetics with coronary artery disease is quite likely to be the ideal blood pressure value for myself and I made certain my primary care guy got a copy of this study. There is a need for more studies like this to ensure that doctors' office practices are based on fact and not habit or custom.

Duane Graveline MD MPH
Former USAF Flight Surgeon
Former NASA Astronaut
Retired Family Doctor

Updated February 2016


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