High blood pressure increases the risk for major health problems, like heart failure, stroke, kidney damage, blindness.

If blood pressure drops too low, the heart muscle may not get enough oxygen.

One study found risk for a heart attack doubles when diastolic pressure is lower than 70 and quadruples when diastolic pressure drops below 60.

A study, published in the journal Neurology, is the largest to look at the link between high blood pressure and memory problems.

No one knows why African-Americans tend to have a higher risk for hypertension. One controversial hypothesis, known as the Middle Passage theory, is that black people who survived the harrowing trip across the Atlantic Ocean from Africa in the holds of ships did so because their bodies were better able to preserve salt, allowing them to avoid death by dehydration. Therefore, the theory goes, some African-Americans have a higher prevalence of “salt-sensitive hypertension”: Their blood pressure increases by unusually high amounts in response to salt.  Isolation of the MYH9 gene does not necessarily refute the theory

About 65 million Americans (roughly one in three adults) have high blood pressure.

Salt-sensitive patients are over three times more likely to experience a heart attack or stroke than those who are not salt sensitive.

Even people with “normal” blood pressure can be salt sensitive.

Researchers are looking for specific genetic links to salt sensitivity that may help them predict which patients are at risk for the problem.