High blood pressure? Exercise!

We know that regular exercise is just one of the ways those with higher blood pressures can help improve their blood pressures. Yet we don't know that regular exercise necessarily leads to lower risk of death from all causes or from heart disease.

It's plausible, certainly: Given that more exercise means better blood pressure scores, and better blood pressure scores mean lower risk of death, you would be reasonable in thinking that if you exercised more that you'd be at a lower risk of death.

Ordinarily we would caution you that medicine is not math: the algebraic equation of if A = B and B = C, then A = C, does not usually apply. Today's research seems to demonstrate one of the exceptions.

In a large-scale, long-term study in Denmark (Hypertension 2019;74:1307-1315), a team of researchers surveyed over 18,000 adult men and women every four years starting in 1976. Along with gathering demographic information such as age, gender, and education, the authors also inquired about medical history, risk factors for heart disease, and the participants' customary levels of activity, grouping them into inactive (sedentary), light activity, and moderate/high levels of activity.

Each participant also submitted to a blood pressure test every four years, coinciding with their responses to the demographic and health questionnaire.

After an average follow-up of over 20 years, the authors accessed the Danish National Patient Register to find out who, among their participants, had passed away, as well as the cause of their death.

For their research the scientists had grouped their participants in 4 levels of blood pressures, matching the levels set by the World Health Organization:

• Normal blood pressure: under 120/80
• Prehypertension: systolic blood pressure (the top number) between 120-139 OR diastolic blood pressure (the bottom number) over 80-89
• Stage I hypertension: systolic blood pressure between 140-159 OR diastolic blood pressure over 90-99 (or those taking medication for hypertension)
• Stage II hypertension: systolic blood pressure at least 160 OR diastolic blood pressure at least 100

For their analysis the authors took into account gender, age, smoking status, education, Body Mass Index, and health variables such as diabetes status.

What's very interesting is that the researchers found that higher levels of physical activity had basically the same effects on all-cause mortality, regardless of whether the participants' blood pressures were normal, prehypertensive, or clinically hypertensive. On the other hand, death from stroke or heart attack - cardiovascular events, specifically - were further reduced.

That is, compared to those who were sedentary,

• Those with normal blood pressures who engaged in light activity were 24% less likely to die of any cause, while the same folks who exercised at the moderate or high activity level were 32% less likely to die of any cause. The estimates for risk of death from cardiovascular events such as stroke or heart attack were similar.
• Those with prehypertension reduced their risk of all-cause mortality 16% with light activity and 24% for moderate/high levels of activity - but they also reduced their risk of death from cardiovascular events by 19% with a minimum of light activity.
• Those with Stage I hypertension reduced their risk of all-cause mortality by 22% with light activity and 31% for moderate/high levels of activity, and reduced their risk of cardiovascular events about the same amount for light activity but 41% for moderate or high levels of activity
• Those with Stage II hypertension reduced their risk of all-cause mortality by 18% with light activity and 28% with moderate/high levels of activity, but they also reduced their risk of death from cardiovascular causes by 26% for light activity and slightly more for moderate-to-high levels of activity.

What this means for you

This is another study that shows correlation and does not prove that exercise specifically prevents death. That said, we physicians have customarily advised our patients with Stage II hypertension to avoid exercise, believing that the increase of blood pressure due to exercise could present a health risk. This study would seem to contradict that belief.

The take-home message here is that exercise can almost certainly help improve your blood pressure and is unlikely to do any harm to those who already have high blood pressure. Even better news is that it doesn't take all that much exercise to make a difference.

For this study, for example, the authors designated "light activity" as "engaging in light physical activity for 2-4 hours per week [up to 35 minutes per day]" - with "light physical activity" being defined as activity that doesn't cause you to break a sweat, such as a stroll through the mall or a casual bike ride.

"Moderate activity" was defined as "engaging in light physical activity for more than 4h/wk [35 minutes per day or more] or more vigorous activity for 2 to 4h/wk," such as brisk walking, fast cycling, or sports that cause you to break into a sweat or become tired.

If you are already active, great! If you aren't and would like to be, check with your doctor to make sure you are cleared for exercise. Discuss with them the type of exercise you would like to pursue, and remember that starting with something as simple and familiar as walking is great for you - you don't have to be a competitive athlete to reap the benefits of exercise.

First posted: November 20, 2019