Most people have had their blood pressure checked at a doctor’s office, pharmacy, or hospital. The test only takes a few seconds, but the results can reveal a lot about a person’s health.
Blood pressure readings are shown as two numbers, such as 120 over 80. For many years, doctors mainly focused on the top number because it was believed to be the strongest warning sign for heart disease.
Now, a massive new study suggests that the bottom number is also very important and should not be ignored.
The research was carried out by scientists at Kaiser Permanente, one of the largest healthcare organizations in the United States. The study examined more than 36 million blood pressure readings collected from about 1.3 million adults living in Northern California over a nine-year period from 2007 to 2016.
Because of its enormous size, the study is considered one of the largest ever conducted on blood pressure and heart disease risk.
The findings were published in the New England Journal of Medicine, one of the world’s leading medical journals.
To understand the study, it helps to know what blood pressure numbers actually mean. Blood pressure measures the force of blood pushing against the walls of the arteries as the heart pumps blood through the body.
The top number is called systolic blood pressure. It measures the pressure when the heart contracts and pushes blood into the arteries. This number has long been considered the most important because high systolic pressure strongly increases the risk of heart attacks, strokes, heart failure, and kidney disease.
The bottom number is called diastolic blood pressure. It measures the pressure inside the arteries when the heart relaxes between beats and fills back up with blood. Although doctors have always recorded this number, it has sometimes received less attention compared to systolic pressure.
In recent years, some experts even questioned whether the diastolic number mattered very much on its own, especially in older adults.
This new study challenges that idea.
The researchers found that both systolic and diastolic blood pressure are linked to serious health risks. Even though the systolic number still had the strongest connection to heart disease and stroke, the diastolic number also independently increased risk when it was too high.
In other words, people with elevated diastolic pressure were more likely to experience heart attacks or strokes, even after accounting for the systolic number.
The findings remained consistent under both old and new blood pressure guidelines.
For many years, doctors often used 140 over 90 millimeters of mercury, written as 140/90 mm Hg, as the main definition of high blood pressure. More recently, newer guidelines lowered the threshold to 130/80 mm Hg because studies showed that lower blood pressure targets may better protect the heart and blood vessels.
Some people questioned whether lowering the targets too much would lead doctors to over-treat patients. However, the new research supports the idea that both numbers matter and that paying attention to slightly elevated readings may help prevent serious disease in the future.
High blood pressure is extremely common around the world. Millions of people live with hypertension without realizing it because the condition often causes no symptoms in the early stages. For this reason, high blood pressure is sometimes called a “silent killer.”
Over time, elevated pressure damages blood vessels and forces the heart to work harder. This can slowly injure the arteries, brain, kidneys, and other organs. If left untreated, hypertension greatly increases the risk of heart attack, stroke, kidney failure, and even dementia later in life.
Doctors say this study highlights why regular blood pressure checks remain so important. A simple reading can provide valuable information about future health risks.
The research also reminds patients that blood pressure management is not only about one number. Both the top and bottom readings offer important clues about how well the heart and blood vessels are functioning.
The lead researcher, Dr. Alexander C. Flint, explained that both measures should continue to be considered when doctors evaluate cardiovascular risk. Ignoring the bottom number may cause some important warning signs to be missed.
Fortunately, there are many effective ways to lower blood pressure and protect heart health.
Lifestyle changes are often the first step. Eating a healthy diet rich in fruits, vegetables, whole grains, and low-fat foods can help reduce blood pressure naturally. Reducing salt intake is also important because too much sodium causes the body to hold extra fluid, which raises pressure inside blood vessels.
Regular exercise can strengthen the heart and improve blood circulation. Even simple activities like walking every day can make a difference. Maintaining a healthy weight, quitting smoking, managing stress, and limiting alcohol can also improve blood pressure control.
For some people, lifestyle changes alone are not enough, and medication may be needed. Modern blood pressure medicines are generally very effective and can greatly lower the risk of heart attack and stroke when taken correctly.
Researchers say the study is another example of how medical science continues to evolve. As scientists gather larger amounts of health data, they can better understand which risk factors truly matter and how doctors can improve prevention strategies.
The findings also send an important message to the public: understanding your blood pressure numbers could help save your life. Paying attention to both the systolic and diastolic readings gives a fuller picture of heart health and may help detect problems earlier.
If you do not know your blood pressure numbers, doctors recommend having them checked regularly, especially as you get older or if you have risk factors such as obesity, diabetes, smoking, or a family history of heart disease.
Keeping both numbers in a healthy range may be one of the best ways to protect your heart, brain, and overall health for the future.
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