Understanding the Scale of Asthma

Asthma affects a large number of people across the globe. According to estimates, around 262 million people were living with asthma in 2019, and the condition caused approximately 455,000 deaths that year^[5]. In the United States alone, nearly 28 million people have asthma^[4], making it one of the most common long-term diseases affecting both children and adults^[8]. About 1 in 13 people in the United States live with this condition^[3].

Asthma is particularly notable as the most common chronic disease among children^[5]. While it often starts during childhood, asthma can develop at any age. Some people might experience symptoms only during childhood, while others develop asthma later in life as adults^[1].

The impact of asthma varies greatly across different parts of the world. Most asthma-related deaths happen in low- and lower-middle-income countries, where people often face challenges in getting proper diagnosis and treatment^[5]. This highlights how access to healthcare and proper management can make a life-or-death difference for people living with asthma.

Despite how common asthma is, many people do not have their condition properly controlled. Research shows that 62% of adults with asthma in the United States do not have adequately controlled symptoms^[15]. This means that more than half of adults with asthma continue to struggle with symptoms that could be better managed with appropriate treatment and care.

What Causes Asthma

Scientists and doctors are not completely certain about what causes asthma to develop in the first place^[1]. The exact reasons why some people develop asthma while others do not remain partially mysterious. What experts do know is that asthma involves long-term inflammation in the airways of the lungs^[1].

The condition causes changes in how the airways function. When someone has asthma, the inside walls of their airways can become inflamed and swollen^[2]. These airways are the tubes that carry air in and out of the lungs, and when they are affected by asthma, they become sensitive to certain triggers. This inflammation is not temporary—it stays present over time, which is why asthma is called a chronic condition, meaning it lasts for a long time or permanently^[1].

While the root cause is not fully understood, researchers have identified that asthma is caused by both inflammation and muscle tightening around the airways^[5]. During an asthma episode, the airways not only swell but also produce extra mucus, which further blocks the passage of air. Mucus is a sticky, protective liquid that normally helps shield the lungs from irritants like dust and smoke^[6]. However, in asthma, the airways make more mucus than usual, which contributes to breathing difficulties.

Risk Factors for Developing Asthma

Even though the exact cause of asthma is not fully known, several factors can increase the likelihood of developing the condition. Understanding these risk factors can help identify who might be more vulnerable to asthma.

Family history plays a significant role in asthma risk. If your biological parents have allergies or asthma, you are at higher risk of developing the condition yourself^[1]. This suggests that genetics contribute to whether someone develops asthma.

Living with certain other conditions also increases asthma risk. People who have allergies or eczema—a condition that causes itchy, inflamed skin—are more likely to develop asthma^[1]. This connection between allergies, eczema, and asthma is sometimes called atopy, which refers to a tendency to develop allergic conditions.

Early life experiences matter considerably. Children who experienced repeated respiratory infections, such as RSV (respiratory syncytial virus), during childhood are at greater risk^[1]. Young children who wheeze frequently and have frequent respiratory infections that continue beyond 6 years of age face greater risk of developing asthma^[6].

Environmental exposures, especially early in life, contribute to asthma risk. Being exposed to toxins, fumes, or secondhand smoke can increase the chances of developing asthma, particularly when these exposures happen early in life^[1]. Even thirdhand smoke—the residue left behind after smoking—poses risks^[1].

Common Symptoms of Asthma

Asthma symptoms can vary greatly from person to person. Some individuals experience symptoms all the time, a pattern called persistent asthma. Others feel fine between episodes and only have symptoms during asthma attacks, which is known as intermittent asthma^[1].

The main symptoms of asthma are problems with breathing. These include wheezing, which is a whistling or squeaky sound when you breathe, especially when breathing out^[6]. Shortness of breath is another common symptom—people may feel like they cannot catch their breath or feel breathless, as if they cannot get air out of their lungs^[6].

Chest tightness, pain, or pressure frequently accompany asthma. This can feel like something is squeezing or sitting on your chest^[1]. Coughing is also a major symptom of asthma. Sometimes coughing is worse at night or early in the morning, making it hard to sleep. For some people, coughing can be the only symptom they experience, a type called cough-variant asthma^[1].

Symptoms can be mild or severe, and they usually come and go over time^[2]. They may worsen at night and early in the morning^[5]. When symptoms become significantly worse, this is known as an asthma attack. During an attack, breathing becomes very difficult, which can be life-threatening^[7].

Various triggers can bring on symptoms or make them worse. These include exercise, high levels of air pollution, cold air, or contact with something you are allergic to, such as pollen, dust, mold, or animals^[7]. Coughing or wheezing attacks may worsen when you have a respiratory virus, such as a cold or the flu^[2].

Preventing Asthma Symptoms

While there is currently no way to prevent someone from developing asthma in the first place, there are many effective ways to prevent asthma symptoms from occurring or becoming worse. The most effective way to control asthma is to manage and avoid triggers^[17].

Identifying your personal triggers is an essential first step. Asthma triggers vary from person to person, so recognizing what affects you specifically helps you reduce exposure to those triggers^[23]. Common triggers include allergies to things like pollen, dust mites, and pet dander. Cold air, especially in winter, can trigger symptoms. Exercise, particularly intense physical activity and cold-weather sports, may bring on symptoms. Mold can trigger asthma even if you are not allergic to it^[1].

Workplace exposures matter for some people. Substances like sawdust, flour, glues, latex, and building materials can cause occupational asthma or trigger attacks^[1]. If you have occupational asthma, even low levels of allergens can trigger symptoms, so removing yourself from what triggers symptoms at work is important^[19].

Respiratory infections like colds, flu, and other respiratory illnesses commonly trigger asthma symptoms^[1]. Staying up to date with vaccinations can help prevent some of these infections. Smoke from smoking, secondhand smoke, and thirdhand smoke should be avoided. Stress, whether physical or emotional, can trigger symptoms. Strong chemicals or smells like perfumes, nail polish, household cleaners, and air fresheners may cause problems^[1].

To avoid triggers at home, several practical steps can help. If animal fur triggers your asthma, keep pets with fur out of your home or at least out of bedrooms. Remove dust and mold from your house through regular cleaning. Keep windows closed and avoid intense outdoor activity when air quality is low or allergen levels are high^[19].

Managing humidity levels in your home can also help. High humidity can promote the growth of mold, dust mites, and other harmful bacteria, while extremely low humidity can dry out the air and irritate your nose and lungs. The ideal humidity is between 30% and 50%^[23].

Working with your doctor to treat other conditions that can interfere with controlling your asthma is also part of prevention^[19]. Physical activity should not be avoided even if it triggers asthma, as it is important for overall health. Instead, speak to your doctor about strategies to help you stay active safely^[19].

How Asthma Changes Normal Body Function

To understand asthma, it helps to know how normal breathing works. The airways are tubes that carry air in and out of your lungs. During normal breathing, air flows freely in and out^[6]. When someone has asthma, several changes occur in these airways that make breathing difficult.

First, inflammation develops in the airways. This inflammation is chronic, meaning it persists over time. The inflammation makes the airways react strongly to certain triggers^[1]. When airways are inflamed, their inside walls become swollen. In addition to swelling, membranes in the airway linings may secrete excess mucus^[2].

When an asthma attack or episode occurs, multiple changes happen at once. The sides of the airways in the lungs swell up. The airways become narrower through a process called bronchospasm, where the muscles surrounding the airways tighten^[1]. At the same time, the airways produce and fill with mucus, which clogs them up^[8].

All these changes work together to make it harder for air to move through the airways. Less air gets in and out of the lungs during an asthma attack^[8]. This explains why people with asthma experience symptoms like difficulty breathing, wheezing, and coughing.

The airways become smaller during an asthma attack, similar to how branches of a tree are smaller than the tree trunk. As air moves through the lungs, the airways normally become smaller and smaller. During an asthma attack, these already-small passages become even more restricted^[8].

What makes asthma particularly challenging is that the airways are overly sensitive. They react to triggers that would not bother people without asthma. Things like pollen, exercise, or cold air can set off this reaction^[1]. This heightened sensitivity is a key feature of asthma that distinguishes it from other breathing problems.

The inflammation in asthma is long-term and ongoing. Even when someone with asthma feels fine and has no symptoms, the inflammation in their airways remains present. This is why asthma requires ongoing management and treatment, not just treatment during attacks. The goal of treatment is to reduce this underlying inflammation and prevent the airways from reacting so strongly to triggers.