There's little doubt that we're a hyper nation. As in hypertensive.
But just how many Americans have blood pressure well outside the normal ranges -- and how many of them have the condition under control -- remains a bit uncertain.
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Normal blood pressure lies anywhere at or below 120 over 80 millimeters (the first number is the beating-heart pressure; the second, the heart at rest). Any numbers 140/90 or above is considered high blood pressure; the zone in between is labeled pre-hypertension.
Having high blood pressure is a major risk factor for heart disease and stroke.
According to a September report issued by the Centers for Disease Control and Prevention, nearly 1 in 3 American adults -- 67 million -- have high blood pressure, and 36 million of them don't have it under control, even though most are under a doctor's care and being treated with medicine.
But a second report, also done by researchers at CDC's National Center for Health Statistics, published in October, took a more glass-half-full approach to basically the same numbers.
They looked at in-person interviews done with about 9,300 hypertensive participants in the National Health and Nutrition Examination Survey between 2001 and 2010.
The survey showed that, in 2001, just 29 percent had controlled blood pressure, versus 47 percent in 2010. In between, in 2003, national guidelines for treating high blood pressure were issued.
Those guidelines advocated using a combination of two or more blood-pressure medicines to achieve adequate control, and the surveys showed that two-thirds of those taking combination therapy had controlled blood pressure in 2010.
Yet the researchers noted that nearly half of the high-blood-pressure population is still not being treated with any combination therapy.
Still, there's not uniform agreement on just what numbers out of the "normal" range mean.
A 2011 study that also used health-survey data going back to the early 1960s and followed subjects for two decades concluded that people with abnormal blood pressure are not actually more likely to die prematurely than those with blood pressure in the normal range.
Scientists led by Dr. Brent Taylor from the Veterans Affairs Health Care System in Minneapolis and the University of Minnesota found that in those under age 50, the resting-heart pressure is better at predicting mortality, while for those over 50, the beating-heart reading is a better risk measure. The study appeared in the Journal of General Internal Medicine.
Taylor said this suggests that more than one approach for defining abnormal blood pressure might be needed, writing: "If we cannot reliably see an effect on mortality in a large group of individuals followed for 20 years, should we define the condition as abnormal?"
Hypertension's effects on other structures in the body are gradual, but many studies suggest it starts early. One report from the University of California, Davis, published in Lancet Neurology found that high blood pressure could harm the brain's structure and function in people as young as 40.
Although the nearly 600 subjects in the study had no cognitive disability when they were examined, there was damage to the structural integrity of the brain's white matter and the volume of its gray matter, and the scientists note that the changes could be associated with a greater likelihood of dementia and Alzheimer's disease later in life.