Blood pressure measures the force exerted by circulating blood against artery walls. This measurement includes two numbers: systolic pressure (force when the heart beats) and diastolic pressure (pressure when the heart rests between beats). Maintaining a healthy range is important because consistently high force can damage blood vessels, increasing the risk of cardiovascular events. In 2017, major professional organizations, including the American College of Cardiology (ACC) and the American Heart Association (AHA), updated their guidelines, dramatically altering the definition of high blood pressure.
Defining the New Blood Pressure Categories
The 2017 guidelines significantly lowered the threshold for diagnosing high blood pressure based on new evidence. Under previous standards (JNC 7 guidelines), hypertension was defined as 140/90 mm Hg or higher. The current guidelines lowered this diagnosis to 130/80 mm Hg, resulting in many more Americans being classified as having high blood pressure.
The revised categories begin with Normal blood pressure, defined as a systolic reading below 120 mm Hg and a diastolic reading below 80 mm Hg. The category previously termed “prehypertension” was replaced by Elevated blood pressure, which is a systolic reading between 120 and 129 mm Hg and a diastolic reading below 80 mm Hg.
Stage 1 Hypertension is diagnosed when the systolic pressure is between 130 and 139 mm Hg, or the diastolic pressure is between 80 and 89 mm Hg. Stage 2 Hypertension is reserved for readings of 140/90 mm Hg or higher. This means the former definition of hypertension is now considered Stage 2.
The Research That Drove the Change
The scientific justification for this reclassification stemmed primarily from the findings of the Systolic Blood Pressure Intervention Trial (SPRINT). This large-scale randomized clinical trial studied over 9,300 adults aged 50 and older who were at increased cardiovascular risk but lacked diabetes or a history of stroke. The trial compared the effects of two different treatment goals for systolic blood pressure.
One group aimed for a standard treatment goal of less than 140 mm Hg, while the other aimed for an intensive goal of less than 120 mm Hg. The trial was stopped early because the intensive treatment group showed such significant benefit. Participants in the intensive group achieved an average systolic reading of 119.2 mm Hg, compared to 135.8 mm Hg in the standard group.
The intensive lowering of blood pressure reduced the rate of the primary composite outcome—including heart attack, stroke, heart failure, and cardiovascular death—by 25%. The intensive treatment also reduced the overall risk of death from any cause by 27%. These results provided evidence that cardiovascular risk begins at a lower pressure than previously acknowledged, and that targeting a systolic pressure below 130 mm Hg offers protection, especially for high-risk individuals.
The SPRINT trial demonstrated that the benefits of tighter blood pressure control outweighed the risks associated with the extra medication required to reach the lower goal. On average, the intensive arm required one additional antihypertensive medication to achieve the target. This data established a clear link between a lower blood pressure goal and reduced major adverse cardiac events, leading the ACC/AHA task force to adopt the 130/80 mm Hg threshold for hypertension.
What This Means for Diagnosis and Treatment
The immediate consequence of the new guidelines was a substantial increase in the number of people diagnosed with hypertension, with the national prevalence rising from about 32% to 46% of the adult population. This reclassification has helped healthcare providers identify individuals at increased risk much earlier, allowing for preemptive intervention.
A diagnosis of Stage 1 Hypertension (130–139/80–89 mm Hg) does not automatically mean a prescription for blood pressure medication. The guidelines emphasize a risk-stratified approach to treatment. For low-risk adults with Elevated blood pressure or Stage 1 Hypertension who do not have other cardiovascular risk factors, the primary intervention is intensive lifestyle modification.
These modifications include dietary changes, regular physical activity, and weight management, which should be attempted for three to six months before considering medication. Drug therapy is recommended immediately for any patient with Stage 2 Hypertension. It is also recommended for those with Stage 1 Hypertension who have known cardiovascular disease or a high predicted risk (10% or greater) of a heart attack or stroke within ten years. The goal for most patients with confirmed hypertension is to achieve a blood pressure below 130/80 mm Hg.