Keeping one's blood pressure levels in the normal range is important. Blood pressure that's too high (hypertension) can cause severe headaches, blurred vision and may even lead to heart disease or stroke. And blood pressure that's too low (hypotension) can cause symptoms like light-headedness, confusion and nausea.  

To prevent such issues, it's essential to have one's blood pressure checked regularly starting at age 18, per Mayo Clinic. When doing so, however, it may be helpful to know that many conditions and outside factors can affect one's blood pressure readings and that blood pressure can change with age as well. 

What is blood pressure?

Blood pressure is simply a measure of how healthy one's heart is by checking the force at which it pumps blood around the body and the time it takes to rest between heartbeats. Blood pressure is measured using two numbers that are typically recorded as one number over another. The top number shows one's systolic blood pressure and represents the force at which one's heart pumps blood through the arteries. The bottom number shows one's diastolic blood pressure, which measures how much the heart rests between heartbeats. 

Per the National Institutes of Health (NIH) National Institute on Aging, normal blood pressure for most adults is defined as a systolic pressure of less than 120 and a diastolic pressure of less than 80, written as 120/80.

Why does blood pressure change as we age? 

"Normal" is the operative word there as several factors can affect blood pressure. These include one's family history, certain medications, and some conditions such as kidney disease, sleep apnea and thyroid issues. Gender also plays a role as women are more likely to have higher pressure after menopause, though men commonly have higher rates of hypertension than women before that point. 

And because one's network of blood vessels, known as the vascular system, changes as we get older, age can also impact blood pressure. "It is important to understand that the components that make up our blood pressure includes any resistance our heart has to push against," explains Viet Le, PA-C, associate professor of preventive cardiology and physician associate at Intermountain Health.

This matters because, "as we age, our arteries lose elasticity and essentially become stiffer which can affect how much blood the heart needs to push in the same way that blowing into a balloon that has not been stretched beforehand takes much more effort than blowing into it after you have stretched it," he says. 

What's more, heart muscle tissue may also thicken as we get older, "which can also reduce the volume of blood that can be contained in the pumping chambers of the heart," Le explains. "While both a slower heart rate and reduced volume may result in slightly lower cardiac output, ultimately, the force or pressure the heart needs to create to overcome stiffening arteries becomes higher, leading generally to higher blood pressures as we age." 

What is normal blood pressure by age? 

Because of such factors, the American Heart Association and the American College of Cardiology recommend for individuals who are 65 or older to aim for a blood pressure level of 130/80.

Blood pressure can also be affected on the other end as well since children and teens are generally smaller in size than adults, with more elasticity in their organs. "Because the heart doesn't have to work as hard (in younger ages), we expect their blood pressure to be lower, with the systolic pressure to be between 95-115 and their diastolic to be between 55-75," Le explains. 

This isn't always the case, however, and because of other potential factors and conditions that may affect matters, it's best to have one's blood pressure checked regularly by a physician to ascertain the most appropriate blood pressure level for each individual. "'Normal' blood pressures can and should be gauged differently for different age groups," says Le.

More:High blood pressure can become a dangerous health problem: What you need to know to lower it