He was known as Joe Cool, a quarterback who never seemed to feel the pressure, even in the biggest games. And Joe Montana, four-time Super Bowl champion, said he really is pretty relaxed.

"I don't get mad easily," said the Western Pennsylvania native, known for calmly leading teams to come-from-behind victories. "I don't raise my voice very often."

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Yet those qualities couldn't keep him from experiencing a potentially deadly kind of pressure. Like millions of other Americans, he suffers from high blood pressure, also known as hypertension.

Since he was diagnosed with the problem in 2002, the former standout at Ringgold High School in Washington County has become a spokesman for a blood pressure awareness campaign sponsored by Novartis Pharmaceuticals Corp.

This month, the company released "Joe Montana's Family Playbook for Managing High Blood Pressure," a free book that features Mr. Montana and his wife, Jennifer. It contains information about the disease and tips for getting it under control.

There are also a few recipes, "tweaked to make them a little bit healthier," Mr. Montana said in a telephone interview.

Doctors note that even though most patients lack symptoms, high blood pressure increases the risk for developing other health problems, including heart disease and stroke.

"It's been labeled 'the silent killer,' " said Dr. T. Barry Levine, a cardiologist and vice chairman of medicine at Allegheny General Hospital.

"People walk around feeling fine with high blood pressure. But over time -- and we're talking years -- it takes a toll."

Blood pressure -- the pressure of the blood against arteries -- is expressed as a range. Readings of 140/90 or higher indicate hypertension, but doctors recommend pressures no higher than 120/80 and emphasize that in general, the lower the pressure, the better.

Experts suggest that increased obesity and an aging population have contributed to a greater prevalence of the disease. A 2004 study found that about 65 million Americans, or one in three adults, had hypertension, up from about 50 million in the early 1990s.

Left unchecked, high blood pressure can damage the lining of blood vessels, leaving them more susceptible to coronary artery disease. Hypertension also increases the risk for heart attack, heart failure, eye damage, stroke and kidney disease.

Yet 30 percent of people with hypertension don't know they have it, according to the American Heart Association. Because people with the disease usually feel no symptoms, they may not see a need to have their blood pressure checked. Mr. Montana found that he had hypertension during a routine physical examination.

Among those who are aware, only about half have their high blood pressure under control.

While many effective medications are available, lowering high blood pressure can be a challenge because patients often need to make lifestyle changes that may include quitting smoking, losing weight, exercising regularly and limiting salt intake.

Making those changes can be difficult for Americans conditioned to waiting in drive-through lines for fast food, much of it laden with salt and calories, said Dr. Daniel Edmundowicz, director of preventive cardiology at the University of Pittsburgh Medical Center's Cardiovascular Institute.

"This is one of the frustrating things about treating hypertension," said Dr. Levine. "Most people aren't symptomatic, and they walk around with this time bomb ticking away.

"It's hard to convince people who feel perfectly fine that they need to be worried and change their lifestyles and take their medications."

While certain kidney or blood vessel problems can cause high blood pressure, the cause is unknown in most cases.

Some people are more likely to develop high blood pressure, including African-Americans, older people and those, like Mr. Montana, with a family history of the disease.

Other factors that increase the risk for developing hypertension can be controlled.

Being overweight and inactive are key risk factors, and reaction to stress appears to matter in some patients, said Dr. Karen Matthews, a professor of psychiatry, epidemiology and psychology at the University of Pittsburgh School of Medicine.

She led a study published in 2004 in the journal Circulation that found that younger adults who had a large blood pressure response to psychological stress may be at risk for hypertension later on.

An ambulatory blood pressure monitor can be used, along with a diary to report stressful periods, to help determine whether a patient's hypertension is affected by stress, Dr. Matthews said. She noted that some of those people may appear outwardly calm.

For many patients, lifestyle changes alone may be enough to control hypertension, Dr. Edmundowicz said. But others need one or more medications.

When the first medication he took didn't work, Mr. Montana, 50, switched to another that has been effective.

He often exercises five or more days a week, walking rather than running on a treadmill because of a bad knee. He also limits his food portion sizes and watches what he eats.

Mr. Montana's weight, nearly 220 pounds when he was diagnosed four years ago, is down to 206, a few pounds heavier than during his playing days.

His message, he said, is that people need to find out their blood pressure and, if it's high, make the changes needed to lower their risk.

Waiting until a health crisis occurs "is not the way to find out about it," he said, "especially when we have such great medications and great, simple ways to change your lifestyle."

To order a free copy of "Joe Montana's Family Playbook for Managing High Blood Pressure," visit www.getbpdown.com or call 1-877-438-2736.