Blood pressure guidelines

The National Institutes of Health conducted a study called the Systolic Blood Pressure Intervention Trial (SPRINT). Two months ago, data flowed from the study that may result in a change in long-held medical guidelines. Whereas previously a systolic blood pressure of 140 (millimeters of mercury) was generally considered not to be a cause of great concern, lowering that number to below 120 yielded a massive decrease in mortality and in serious adverse incidences.

Heart attacks, heart failure and strokes were reduced by almost a third in a cohort of over-50 adults, and deaths decreased in this group by almost a quarter, compared to the target systolic pressure of 140mm Hg.

Participants in the SPRINT study had to fit a particular health and age profile. In addition to all SPRINT subjects being over age 50, the trial only enrolled subjects if they had an elevated blood pressure and increased cardiovascular risk. So, is the SPRINT study exactly analogous to us? Does it have direct and parallel utility for healthy triathletes? We'll explore the relevance of this study's findings for us.

The SPRINT study includes data from more than 9,300 participants living in the U.S. and Puerto Rico. Cohorts received treatments labeled "standard" and "intensive," the former cohort having their systolic pressure lowered to 140mm Hg using a combination of drugs, the latter lowered to 120mm Hg.

An estimated 1 in 3 adults in the United States has high blood pressure according to the CDC. Stage-1 high blood pressure is when the systolic pressure is between 140–159 or the diastolic is between 90–99. The top number of your blood pressure reading is systolic, which is your blood pressure when the heart beats, that is, at the moment it is pumping blood. Diastolic is the lower number and is the pressure when the heart is at rest, in between beats.

Stage-2 is when systolic is at or above 160 or the diastolic threshold hits 100.

Blood pressures of 120–139 or 80–89 respectively have been labeled pre-hypertension but the SPRINT study suggests, at face value, that blood pressure in this range is still a potential killer. Well established clinical guidelines recommend a systolic blood pressure of less than 140mm Hg for healthy adults. Does the SPRINT study prime these guidelines for a rethink? Remember the study group's profile: these were not "healthy" adults.

Fortunately, most triathletes have a head start on their sedentary neighbors, and they may have an enhanced capacity to control or change behavior. Here's what one Slowtwitcher wrote on our Reader Forum in 2014, because an ace inhibitor gave him unwanted side effects: "Cut out caffeine; cut out sodium (mostly); started doing longer rides; started doing some yoga to relax. As of Saturday, after my long ride, I was at 100/67. That's down from 150/100 with no meds."

There is a view, which may be rooted in fact or may be urban myth, that while some heavily-training endurance athletes have a higher systolic number than considered ideal, this might be okay. Wrote one member of our reader forum, "I'm 130/70 with a resting pulse of 40. Doctors who don't understand athletes see this and caution me about being ‘borderline hypertensive' due to the 130."

"Bingo," answered another reader. "I had to explain the same thing over and over and over again. My GP and my physio get it, most other doctors don't. It's okay though, we're abnormal."

Is this true? Is a fit and trim triathlete's systolic of 130 normal or expected? Is it at least better than a sedentary athlete's 130?

I asked Dr. Lawrence Creswell, a cardiologist at University of Mississippi Medical Center who has done a lot of work in triathlon (Dr. Creswell authors a blog called The Athlete's Heart). He offered that, "I'd rather be a fit, trim triathlete with SBP of 130, rather than a sedentary individual with a SBP of 130."

Dr. Creswell feels that "the first treatment for elevated blood pressure," should be the sorts of things we already do: exercise, eat well, and other lifestyle changes. When asked about our push-pull with salt he said, "Yes, excess salt intake is unhealthy and, perhaps, efforts to decrease excess salt intake may be appropriate. But athletes need to replace salt loss, so salt intake is necessary. "

But he also acknowledges that, "Individuals who already exercise, don't smoke, and have an ideal weight – like many triathletes – often need medication to control elevated BP." A lot of Slowtwitchers report high BP in spite of their training and fitness – maybe it's from participating on our Reader Forum. Some take BP-lowering medication with no side effects. Others report side effects.

"Beta-blockers are poorly tolerated by athletes because they limit the HR in addition to reducing the BP," explains Dr. Creswell. "Diuretics, even weak ones like HCTZ, may be poorly tolerated because of issues with dehydration during exercise. ACE inhibitors or ARB – angiotensin receptor blockers – are often good choices for athletes. For any individual athlete, some experimentation with trial-and-error may be needed to settle on the best medication."

Dr. Creswell noted that, "According to the current JNC8 guidelines, you qualify for the diagnosis of hypertension if the BP is over 140/90 if you're less than 60 years old, or over 150/90 if you're over 60. The goal of treatment with medication for these 2 groups is under 140/90 or under 150/90, respectively."

The image above is of me, taking my own BP about 5 minutes prior to typing this. This is a little high for me, my goal is to keep it in the 120s, but I'm 58 and I suspect my days of 104/60 are long gone.

At face value the SPRINT study might seem to argue for more aggressive intervention, but the study itself concluded that the better outcomes flowing from lower systolic numbers were only demonstrated for those at "high risk for cardiovascular events but without diabetes." The study did not draw conclusions about healthy populations. The study also noted that, "some adverse events occurred significantly more frequently," when medication was used to hit "the lower target."

The high-risk population was chosen for the study because there would be enough adverse events to notice a difference. It's why we test bikes in the wind tunnel at 30mph instead of 20mph: It's hard to detect differences at 20mph. "If you chose an extremely low risk patient population, such as a healthy young triathlete where adverse events are rare," said Dr. Creswell, "it would become impossible to show a benefit of one strategy over another."

Therefore, while the SPRINT study shows a benefit to lowering the systolic BP from 140 to 120 in older, sicker patients, the healthier patient's doctor may choose to medicate one patient and not the other, even if they share an identical blood pressure, if one is otherwise healthy and the other much less so.