JNC Criteria for Normal Blood Pressure and Prehypertension
According to the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7), normal blood pressure is defined as <120/80 mmHg, while prehypertension is defined as systolic blood pressure of 120-139 mmHg or diastolic blood pressure of 80-89 mmHg.
Blood Pressure Classification According to JNC 7
The JNC 7 guidelines established the following blood pressure categories for adults aged 18 and older:
| BP Classification | Systolic BP (mmHg) | Diastolic BP (mmHg) |
|---|---|---|
| Normal | <120 | and <80 |
| Prehypertension | 120-139 | or 80-89 |
| Stage 1 hypertension | 140-159 | or 90-99 |
| Stage 2 hypertension | ≥160 | or ≥100 |
Key Points About Prehypertension
Prehypertension was introduced as a new category in JNC 7 to identify individuals at high risk of developing hypertension. This designation is intended to:
- Alert both patients and clinicians to this increased risk
- Encourage early intervention through lifestyle modifications
- Potentially reduce BP or prevent progression to hypertension
- Address the fact that cardiovascular risk begins to increase at BP levels above 115/75 mmHg
Prehypertension is not considered a disease category but rather a designation to identify individuals who would benefit from preventive measures. The risk of developing hypertension is significantly higher in this group:
- Those with BP in the 130-139/85-89 mmHg range have a 50% chance of developing hypertension within 4 years (for those ≥65 years)
- Those with BP in the 120-129/80-84 mmHg range have a 26% chance of developing hypertension
Clinical Implications
The JNC 7 classification is based on the average of two or more properly measured, seated BP readings on each of two or more office visits. When systolic and diastolic pressures fall into different categories, the higher category should be used for classification 1.
Individuals with prehypertension:
- Are not candidates for drug therapy based solely on their BP level
- Should be firmly advised to adopt lifestyle modifications
- May require drug therapy if they have diabetes or kidney disease and lifestyle modifications fail to reduce BP to ≤130/80 mmHg
Cardiovascular Risk
The relationship between BP and cardiovascular disease risk is continuous, consistent, and independent of other risk factors. For every 20 mmHg systolic or 10 mmHg diastolic increase in BP, there is a doubling of mortality from both ischemic heart disease and stroke 1.
Prehypertension is associated with increased risk for cardiovascular disease (hazard ratio 1.32 [95% CI 1.05-1.65]) even after adjustment for other cardiovascular risk factors 3.
Differences Between Low and High Prehypertension
Research has shown that high-normal blood pressure (130-139/85-89 mmHg) carries a greater cardiovascular risk than low prehypertension (120-129/80-84 mmHg):
- High-normal BP remains a significant predictor of cardiovascular disease after adjustment for other risk factors (HR 1.42 [95% CI 1.09-1.84])
- Low prehypertension shows increased risk in unadjusted analyses but not in adjusted analyses
Important Clinical Considerations
93% of individuals with prehypertension have at least one additional cardiovascular risk factor 3
Individuals who are normotensive at 55 years of age have a 90% lifetime risk for developing hypertension 2
The goal for individuals with prehypertension and no compelling indications is to lower BP to normal with lifestyle changes and prevent the progressive rise in BP 1
By recognizing and addressing prehypertension early, clinicians can help patients implement lifestyle modifications that may prevent or delay the onset of hypertension and reduce cardiovascular risk.