From Ancient Greece through the 18th century, physicians believed that bloodletting expelled bad blood, or humors, from the body, taking disease with it at the same time.

One unintended benefit of this treatment — it temporarily lowered high blood pressure.

While the Ancient Greeks didn't know about the dangers of high blood pressure — also called hypertension — we do. But it turns out that many of us might not know we have it.

A new study of 888 men and women found that 16 percent of them had "masked" high blood pressure that wasn't identified while they were at their doctor's office.

Having unidentified and uncontrolled high blood pressure is dangerous.

Not only does it increase your risk of heart attack and stroke, but new research demonstrates even modest increases in blood pressure can increase risk of heart failure.

Every 10 mm/Hg increase in systolic blood pressure (the top number) increases your risk of death by 12 percent.

High blood pressure is also linked to a higher risk of cognitive decline. The narrowing of blood vessels that contributes to high blood pressure also can mean that there's less blood flowing to the brain.

So get yourself a blood pressure cuff at the drugstore or get tested at your local pharmacy. If you have a top number over 120 or a bottom number over 80, it's time to bring that blood pressure down.

We shoot for 115/75! Your first steps: lifestyle changes like exercising more, proper diet, mindful meditation, and not smoking.

If that doesn't work, talk to your doctor about medication.