Pulmonary hypertension (PH) is a form of high blood pressure that specifically affects the blood vessels between the heart and lungs. These vessels, called pulmonary arteries, carry blood from the heart to the lungs to pick up oxygen. PH can be caused by anything that raises the pressure in these arteries, such as heart or lung disease.

The types of PH are grouped based on their causes and fall into five categories. Though some types can be treated directly, most cases of PH are treated according to their underlying cause. Your treatment plan will depend on the cause of your PH.

This article explains what can lead to PH and outlines seven risk factors that may increase your chances of developing the condition.

Causes of Pulmonary Hypertension

Group 1 PH is caused by pulmonary arterial hypertension (PAH). In PAH, the pulmonary arteries become thick, narrow, or stiff and reduce blood flow. PAH may be caused by:

• Certain inherited gene mutations (changes)
• Congenital heart disease (heart conditions present at birth)
• Other medical conditions, such as connective tissue diseases or blood cell disorders
• Use of prescribed or illicit drugs
• Idiopathic (unknown) causes

Group 1 PH is less common than PH in groups 2 through 5, which may be caused by:

• Certain heart conditions, such as left-sided heart disease, left-sided heart failure, and heart valve problems
• Lung diseases
• Conditions that reduce oxygen levels, such as obstructive sleep apnea (a condition in which breathing repeatedly stops and starts during sleep due to a blocked airway)
• Blood clots in the lungs
• Tumors
• Other conditions, including kidney disease

Pulmonary Hypertension Risk Factors

Both inherited and environmental factors can affect a person’s risk of PH. Researchers believe that PH usually occurs because of a mix of these factors, along with other medical conditions. In some cases, it’s unclear why PH develops.

1. Age and Sex

In general, the risk of PH rises with age. The condition is most common in adults between 30 and 60 years old. According to the Pulmonary Hypertension Association, women are at least 2.5 times more likely than men to develop PAH, especially during their childbearing years. PAH due to an unknown cause is more likely in young adults.

Although rare, PH can also develop in children and infants, usually due to congenital conditions (health problems present at birth).

2. Genes and Family History

In some people, PAH is directly caused by a genetic mutation passed down from a parent. These gene changes can cause an overgrowth of cells in the blood vessels of the lungs, making them narrow. Narrower arteries reduce blood flow, which raises pressure in the heart’s right ventricle and the pulmonary artery.

Having a family member with PH raises your risk. Sometimes, a person develops PAH from a gene change that wasn’t inherited but happened randomly.

Other inherited genes may increase your chances of getting PH when combined with certain environmental factors. Most researchers believe that many genes may influence both the risk of developing PAH and how severe it becomes.

Having a family history of blood clots can also raise your risk of PH.

3. Congenital Heart Conditions

Some people are born with congenital heart defects (CHDs) that increase their risk of PH. CHDs occur when the heart or connected blood vessels don’t form normally before birth, and they affect fewer than 1 percent of people. However, almost 40 percent of people with a defect are at risk of PH, and around 10 percent of them will develop it.

People with shunt lesions — holes in the upper or lower chambers of the heart — have the highest risk. Shunt lesions cause blood to flow the wrong way, from the left side of the heart to the right. This adds extra blood flow to the pulmonary arteries, which can increase pressure and lead to PH.

If healthcare providers recognize CHDs early, it may be possible to repair them before they lead to PH. Without treatment, shunts may damage the blood vessels permanently, which can cause blood to flow in reverse. This results in cyanosis (oxygen-deprived tissue) and is called Eisenmenger syndrome, which can also lead to PH.

4. Certain Medical Conditions

Many people who develop PH have at least one related health condition that increases their risk. Medical conditions commonly linked to PH include:

• Scleroderma — Around 30 percent of people with this connective tissue disease develop PH.
• Sickle cell anemia (also called sickle cell disease) — Between 20 percent and 40 percent of people with this condition develop PH.
• Human immunodeficiency virus (HIV) — An estimated 1 in 200 people with HIV will develop PH.

Through various mechanisms, many other conditions can also increase the risk of PH, including:

• Blood disorders, such as polycythemia vera and essential thrombocythemia
• Chronic obstructive pulmonary disease (COPD)
• Chronic hypertension (high blood pressure)
• Connective tissue disease, such as lupus
• Down syndrome
• Gaucher disease
• Heart disease
• Hereditary hemorrhagic telangiectasia
• Inflammatory diseases, such as sarcoidosis
• Kidney disease
• Liver disease, such as cirrhosis
• Lung diseases, such as emphysema
• Metabolic disorders, such as glycogen storage disease
• Obstructive sleep apnea
• Pulmonary embolism (blood clots in the lungs)
• Pulmonary fibrosis (scarring of the lungs)
• Schistosomiasis (a parasitic infection)
• Thyroid disease
• Tumors that press on the pulmonary arteries

PH can also develop later in life as a result of a splenectomy (surgical removal of the spleen).

5. High Altitude

Living at a high altitude — specifically, at least 8,000 feet (2,438 meters) above sea level — increases the risk of PH. This is because oxygen levels drop as elevation rises. When there’s less oxygen in the air, your body can develop chronic hypoxia (long-term low oxygen), which may trigger PH in at-risk people who have lived for years at a higher altitude.

If you have PH, traveling to high elevations may worsen your symptoms. For example, you might notice that activities like walking or climbing stairs cause more shortness of breath and chest pain than usual. Everyone’s response to elevation is different, so symptoms may vary from person to person.

6. Exposure to Inhaled Toxins

Inhaling certain substances, such as asbestos, over time is also linked to a higher risk of PH. People who work with or remove asbestos can develop asbestosis, a lung disease caused by inhaling asbestos fibers and dust. Asbestosis also leads to lung scarring and thickening around the lungs, which may increase the risk of PH in advanced stages.

Smoking tobacco or using nicotine products may also raise your risk of PH. Although researchers don’t fully understand how nicotine affects the lungs and heart in PH, smoking cigarettes is strongly linked to lung diseases such as COPD, which are known PH risk factors. Some animal studies suggest that exposure to nicotine may contribute to PH, even without other lung diseases, but more human research is needed.

7. Medication or Other Drug Use

Certain prescription or recreational drugs have been linked to PH. Drugs that may increase your risk of PH include certain:

• Antidepressants
• Antiviral medications
• Cancer medications
• Diabetes medications (used for blood sugar control)
• Illicit drugs
• Immunosuppressants
• Weight loss medications

Always tell your doctor about all medications, supplements, or drugs you use. They can help you understand if anything you take may affect your risk of PH. Understanding your risk factors — including your medical history, environment, lifestyle, and genetics — is an important step toward early detection, better management, and improved quality of life with PH.

Find Your Team

On myPHteam, the social network for people with pulmonary hypertension and their loved ones, members come together to ask questions, give advice, and share their stories about life with PH and pulmonary arterial hypertension.

Do you know what caused your PH? Share your thoughts in the comments below, or start a conversation by posting on your Activities page.