High blood pressure may increase the risk of dementia, study says. Doctor shares what to watch for.

NEW YORK -- High blood pressure, or hypertension, may increase the risk of dementia, according to a new study. So how can you lower your risk factors?

Dr. Nidhi Kumar is On Call for CBS New York and explains how nearly 120 million people -- half of adults the U.S. -- are living with the disease. 

What are the symptoms of hypertension?

Blood pressure is the pressure that your blood pushes against your arterial walls, says Dr. Kumar. When that pressure is high, there can be a lot of wear and tear on your organs. 

"The organs that are most vulnerable are your heart, your brain, your kidneys and your eyes," Dr. Kumar explained.

"Now, here's the problem, many people have no symptoms. They don't even realize they have high blood pressure, so it's so important to get your blood pressure regularly checked," she continued. "For some people though, clues that you have elevated pressure can be headache, dizziness, chest pain, shortness of breath, even nosebleeds."

What causes high blood pressure?

Blood pressure typically rises with age, because your body's vessels get stiffer.

"But we're seeing high blood pressure in younger people, and a lot of it are causes that can be reversible, like sleep apnea or poor sleep... Too much stress, not enough exercise, too much salt in the diet... Finally, medications -- cold medications, allergy medications, even over-the-counter birth control pills," said Dr. Kumar.

How is hypertension linked to dementia?

The study from the Journal of Hypertension Research followed approximately 2,000 people in their 40s and 50s with hypertension in Argentina. 

"They had a 30 percent increase of developing dementia later in life," Dr. Kumar said. "So the take-homes from these studies are that middle age is the time to really focus on your risk factors and get them under really tight control."

Setting healthy blood pressure goals

Dr. Kumar says a healthy blood pressure is measured as 120 over 80.

"Really, think as low as possible, try to get your blood pressure numbers below 120 over 80, and lifestyle goes such a long way," she said.