By Stephanie Stahl

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PHILADELPHIA (CBS) — High blood pressure is often called the silent killer because it usually has no symptoms but doctors say it’s something that African-Americans should check.

Five years ago, Tracy Johnson was at work when she suddenly felt extremely warm.

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“The nurse on the site checked my blood pressure and it was 220 over 120 and they sent me straight to the ER,” Johnson said.

Johnson, 46 years old at the time, learned she had high blood pressure, which runs in her family.

high blood pressure Study: Most African Americans Develop High Blood Pressure By Age 55

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New research in the Journal of the American Heart Association shows 75 percent of African-American men and women are likely to develop high blood pressure by age 55, compared to 55 percent of white men and 40 percent of white women.

“Blood pressure is very complex. A part of it relates to the genetic makeup, a part of it relates to diet, lifestyle,” explained Dr. Gautam Visveswaran, a cardiologist.

Researchers also found following a diet designed to stop hypertension lowered a person’s risk. Doctors say high blood pressure is preventable.

“Incorporate a healthy diet which is low salt, high in fruits and vegetables. Get to an exercise program and go to your healthcare provider,” Dr. Visveswaran said.

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High blood pressure is a risk factor for heart disease. Three months ago, Johnson needed surgery for two blockages in her heart.

“When you’re young, you think you’re invincible, so I wasn’t worried about that then but I am now,” Johnson said.

Johnson says she is more diligent now about watching her diet, taking medications, and she has lost some weight and is exercising to stay healthy.

The study also found that having a higher body weight was linked with an increased risk for high blood pressure regardless of race or gender.