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The American Society of Hypertension (ASH) unveiled a new definition and classification system for hypertension at its annual meeting, held May 14–18 in San Francisco.
Drafted by an ASH working group, the new definition is intended to better reflect risk factors and pathology rather than pegging disease to a blood pressure number.
"Hypertension is more complicated than just blood pressure," says Thomas D. Giles, MD, ASH president and chair of the writing group. "It includes all the other factors that we know contribute to cardiovascular risk, including cholesterol, body mass index, and diabetes."
ASH undertook the effort because the existing definitions of hypertension do not adequately reflect the risks posed by the disease, Giles says.
More than 80% of people with hypertension have additional comorbidities, such as obesity, glucose intolerance, hyperinsulinemia, reduced HDL cholesterol, elevated LDL cholesterol, elevated triglycerides, or left ventricular hypertrophy. More than 50% of people with hypertension have two or more comorbidities.
The new ASH definition is intended to reflect risk factors, early markers of disease, and hypertensive target-organ damage that can occur in the kidneys, eyes, arteries, and heart (see sidebar).
EVOLVING CONCEPTS
The new definition is "trying to look at the evolution of vascular disease, together with genetic predisposition, and look at the continuum of risk," says George L. Bakris, MD, of Rush University Medical Center in Chicago. "It's a way to give an appreciation for what hypertension really is, rather than just treating a number."
"People tend to focus on a number—if you're at 141 [mmHg] you're in trouble, while if you're at 138 [mmHg] life isn't so bad," Bakris says. "That's misleading."
The issue was last visited in 2003 by the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC-7), a panel sponsored by the National Institutes of Health.1
HYPERTENSION REDEFINED: A PROPOSAL
"Hypertension is a progressive cardiovascular syndrome arising from complex and interrelated etiologies. Early markers of the syndrome are often present before blood pressure elevation is sustained; therefore, hypertension cannot be classified solely by discrete blood pressure thresholds. Progression is strongly associated with functional and structural cardiac and vascular abnormalities that damage the heart, kidneys, brain, vasculature, and other organs and lead to premature morbidity and death."—American Society of Hypertension Writing Group
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Under the JNC-7 scheme, a systolic pressure of 
120 mmHg and a diastolic
pressure of 80 mmHg is considered normal. Blood pressures >140 mmHg
systolic or >90 mmHg diastolic are considered degrees of hypertension.
JNC-7 was notable for designating a new pre-disease state of hypertension, ranging from 120 to 139 mmHg systolic and 80 to 89 mmHg diastolic. Prehypertension affects about 20% of the U.S. population, or about 45 million Americans.
The ASH writing group will present its report in an upcoming hypertension journal. Members of the panel say they expect to see descriptions of hypertension evolve in clinical research and the medical literature, and eventually reach the primary care setting.
Just how the new concepts will filter into primary care and the lay
public's understanding remains to be seen. "If anything, [the new
definition] will make things more complicated than easier," Bakris says.
"It's a definition that's trying to crystallize what specialists think.
And to give that to primary care, it's going to need language that's more
user-friendly." 
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