Hypertension, also known as high blood pressure, is one of the most common chronic diseases. It is often referred to as a "silent killer" because it shows no obvious symptoms but "significantly increases the risks of heart, brain, kidney and other diseases," according to the World Health Organization (WHO).

Monday is World Hypertension Day. The theme this year is "Measure your blood pressure accurately, control it, live longer!" But how much do you know about the disease?

According to the WHO, normal adult blood pressure is defined as a blood pressure of 120 millimeters of mercury (mm Hg) when the heart beats (systolic) and a blood pressure of 80 mm Hg when the heart relaxes (diastolic).

"When systolic blood pressure is equal to or above 140 mm Hg and/or a diastolic blood pressure equal to or above 90 mm Hg, the blood pressure is considered to be raised or high," said the WHO.

Risk factors for hypertension

If active intervention is not taken, hypertension will lead to health problems, including chest pain or angina pectoris, coronary heart disease, kidney failure and myocardial infarction or heart attack.

The risk factors for the disease include unhealthy diets – consumption high in sodium, salt and fat, obesity, mental stress, drug effects, smoking and drinking and physical inactivity.

The WHO also lists "a family history of hypertension, age over 65 years and co-existing diseases such as diabetes or kidney disease" as non-modifiable risk factors associated with hypertension.

Regular monitoring necessary

An estimated 1.13 billion people worldwide have hypertension, the WHO said in 2019.

In China, cardiovascular and cerebrovascular deaths account for more than 40 percent of the total deaths, of which hypertension is the first risk factor. More than 70 million Chinese under the age of 35 suffer from hypertension, China Central Television (CCTV) reported on Monday.

However, patients are always unaware of the problem, as the disease usually has no symptoms.

"The most common symptoms of hypertension that patients can feel are dizziness and headaches. Some have no symptoms, however. They just find their blood pressure high during a health examination, or occasionally when they measure blood pressure, which should be paid special attention to," Ding Chunhua, director of the cardiology department at the Aerospace Center Hospital, told CCTV.

Experts say adults over 18 years old should regularly monitor their blood pressure – at least once a year. People at high risk of hypertension are overweight, smokers, long-term alcohol consumers, experience long-term mental stress and physical inactivity and should have their blood pressure measured more regularly.

Take your medicine regularly

It's dangerous for patients to lower their blood pressure by overdose or intermittently, experts warned.

"It will cause large fluctuations in blood pressure," said Ding, who recommended patients take long-acting antihypertensive drugs at a proper dose so that their blood pressure can be lowered steadily.

If the patients take drugs when their blood pressure is high but stop when it is lowered, they could have a stroke or damage their other organs, Ding warned.