High blood pressure, clinically known as hypertension, affects nearly 75 million adults in the United States and 1 billion people globally. Although one-third of adults in the United States are affected, only half of them have their blood pressure controlled.
That has significant costs, both in terms of health and economics. The estimated economic burden for hypertension in 2014 was nearly $75 billion worldwide. It is the single largest contributor to death and disability worldwide, in large part because it dramatically increases the risk of stroke, heart attack, heart failure, and chronic kidney disease. For example, starting at a blood pressure of 115/75, the risk of death doubles for every 20 mmHg increase in systolic pressure (the first number), and for every 10 mmHg increase in diastolic pressure (the second number).
Hypertension is the most common reason for office visits in adults (excluding pregnancy) and more prescriptions are written for blood pressure lowering drugs than for any other drug class.
Let’s review the most frequently asked questions about hypertension – and how to treat it.
What is blood pressure and what is hypertension?
Blood pressure (BP) consists of measuring two types of pressure: the systolic pressure generated in the large arteries when the heart (i.e., the left ventricle) contracts, and the diastolic pressure in the system when the heart relaxes.
These days, it is relatively easy for people to measure and track their own blood pressure, either at home or in most drug stores. Quality automated blood pressure machines—preferably using an upper arm cuff—are now available for about $35-$50, which seems an affordable and worthwhile investment for every household.
The diagnosis of hypertension is made when the average blood pressure—measured on several separate occasions—exceeds a systolic pressure of 140 mmHg and/or a diastolic pressure of 90 mmHg.
According to the Joint National Committee (JNC):
- Normal blood pressure is defined as a systolic BP less than 120 mmHg and a diastolic BP less than 80 mmHg.
- Pre-hypertension is defined as a systolic BP between 120-139 mmHg and a diastolic BP between 80-89 mmHg. These individuals do not require drug therapy, but are advised to make lifestyle adjustments because they are at risk to develop hypertension (Learn more about these in the risk factors section below).
- Stage 1 hypertension is defined as a systolic BP between 140-159 mmHg and a diastolic BP between 90-99 mmHg. These individuals usually require treatment with at least one blood pressure lowering drug.
- Stage 2 hypertension is defined as a systolic BP ≥ 160 mmHg and a diastolic BP ≥ 100 mmHg. These individuals should be promptly started on drug therapy with at least two anti-hypertensive agents.
What are the risk factors for developing hypertension?
Above age 40, the systolic BP tends to increase with age in both men and women; in contrast, the diastolic BP increases only to about age 50-55, after which it tends to decline. Therefore, the “pulse pressure” (the difference between the systolic and diastolic pressures) tends to increase with age, most often due to increasing stiffness of the arterial system. The long-term regulation of blood pressure appears to be controlled by the kidney, specifically in the way it handles sodium.
The risk factors for developing hypertension can be divided into those that are unmodifiable, modifiable, and potentially modifiable. Unmodifiable risk factors include age, genetics/family history, race, and the number of nephrons present in the kidneys at birth. A nephron is the fundamental functional element of the kidney, and it is normal to be born with at least 750,000 nephrons in each kidney. Recent studies have suggested that individuals born with lower nephron number are at higher risk to develop hypertension.
Modifiable risk factors are a high salt diet, obesity, physical inactivity, excessive alcohol use, and low vitamin D levels. Potentially modifiable risk factors include diabetes, high levels of lipids, depression, and certain personality traits (the so-called high strung “type A” personality or those with high stress, anxiety, impatience, or hostile attitudes).
What are the potential complications of hypertension?
Hypertension is a major risk factor for disease in the key vascular beds (Vascular refers to the network of blood vessels in the body) of the central nervous system (brain and eye), heart, and kidneys. Neurovascular complications are stroke and damage to the retina; cardiovascular complications include abnormal enlargement of the left ventricle, heart attack, and congestive heart failure; and hypertension is a major cause (and accelerator) of chronic kidney disease (CKD).
Importantly, effective treatment of hypertension decreases the relative risk of ischemic stroke by 30-40 percent, the relative risk of heart attack by 20-25 percent, and the relative risk of congestive heart failure by as much as 50 percent.
What are the guidelines and targets for patients with hypertension?
Despite intensive study for more than 100 years, it is surprising that we still do not know exactly what represents an optimal resting blood pressure. Although experts and various societies have come to general consensus, controversies remain, so we can expect guidelines and recommendations will continue to change, as they have since the first statement from the Joint National Committee (JNC-1) in 1977.
Current goal blood pressure targets depend on age and whether other conditions (e.g., diabetes, coronary artery disease, CKD) are present, as follows:
- Less than 140/90 for the general population less than 60 years old
- Less than 150/90 for the general population 61-79 years old; some recommend 140/90 if possible to achieve without side effects
- Less than 150/90 for the general population ≥ 80 years old
- Less than 140/90 for those with diabetes, coronary artery disease, or CKD at all ages
Note that although 120/80 is considered a normal blood pressure, experts remain uncertain if medications should be used to reach that level
What is the treatment approach to hypertension?
Lifestyle modifications are recommended for all patients. Such recommendations include weight loss for those who are overweight, a heart-healthy diet low in sodium (less than 1500-mg) and high in potassium (e.g., the DASH diet), physical exercise for 150 minutes per week, and modest alcohol consumption.
For stage 1 hypertension (systolic BP 141-159; diastolic BP 90-99), in addition to lifestyle modifications, pharmacologic treatment should be initiated with one of the following drugs:
- Thiazide diuretic (e.g., hydrochlorothiazide)
- Long-acting calcium channel blocker (e.g., amlodipine)
- ACE inhibitor (e.g., Lisinopril)
- Angiotensin Receptor Blocker (e.g., Losartan)
For stage 2 hypertension (systolic BP ≥160 mmHg; diastolic BP ≥100 mmHg), in addition to lifestyle modifications, pharmacologic treatment should be initiated with two of the above drugs, often a thiazide and one other.
Patients should also be given an easy yet effective way to record their progress, such as the “Blood Pressure to Goal” sheets designed by Dr. Virginia Hood (a kidney doctor at the UVM Medical Center). Patients should be warned about potential side effects and be aware of the risk of low blood pressure (hypotension).
Finally, individuals with severe or difficult to control hypertension should be referred to a kidney doctor (nephrologist), especially because a small percentage of those with severe hypertension might have an underlying cause that requires diagnosis and treatment.
Alan Segal, MD, is a nephrologist at The University of Vermont Medical Center where he is also Director of the Nephrology Fellowship Program. He is also an associate professor at the Larner College of Medicine at UVM.