Brittle asthma

What is brittle asthma?

Brittle asthma is an older term used to describe a severe type of asthma. People with brittle asthma have big variations in their symptoms and breathing tests despite being on high doses of asthma treatment. It's also used to describe people who get sudden, severe asthma attacks occurring 'out of the blue', despite having well-controlled asthma.

These types of brittle asthma seem to be very rare, with one estimate being that they affect every 1 in 2000 people with asthma.

Brittle asthma is sometimes used more generally to describe anyone who has frequent asthma attacks or difficult-to-control asthma symptoms, although this is different from the scientific description.

The term 'brittle asthma' is not used as often any more. The international guidelines on asthma classification have stopped using it. Instead, they use two other terms:

• Difficult-to-treat asthma, for people with uncontrolled asthma symptoms or flare-ups despite being prescribed high-dose asthma treatment.

• Severe asthma, for people with uncontrolled asthma symptoms or flare-ups despite being prescribed high-dose asthma treatment that is being used regularly and correctly, and despite any other triggers for asthma being treated or removed (such as smoking).

People previously described as having 'brittle asthma' would probably now be described as having difficult-to-treat or severe asthma. However, healthcare professionals sometimes still use the term.

What are the types of brittle asthma?

One classification of brittle asthma divides it into two types.

Brittle asthma type 1

In asthma, the airways of the lungs narrow, causing asthma symptoms. In asthma, this narrowing varies over time, often during the course of a single day. Airway narrowing and lung function can be measured in different ways; a common way is by measuring peak expiratory flow readings (PEF).

People with untreated or poorly controlled asthma often have reduced PEF readings, and these often go up and down a lot, which is called 'variability'.

Type 1 brittle asthma is when someone is regularly using high doses of inhaled steroids (which are usually enough to control most people's asthma), but still has big changes in their PEF readings each day. Essentially, this means that their asthma is still very active despite high-dose treatment. So, they are likely to have troublesome asthma symptoms very frequently.

Brittle asthma type 2

People with type 2 brittle asthma can suddenly develop severe asthma attacks for no apparent reason, despite having otherwise well-controlled asthma.

This can cause life-threatening attacks of asthma that develop very quickly. These often need treatment in hospital, and can be fatal.

What are the symptoms of brittle asthma?

Brittle asthma causes the same symptoms as other types of asthma, which are:

• Feeling short of breath, out of breath, or tight-chested.

• Wheezing.

• Coughing.

Asthma symptoms tend to come and go over time, sometimes within the same day. They tend to flare up when exposed to certain triggers, such as infections, exercise, smoke exposure, or cold weather. Asthma symptoms are often worse at night.

In brittle asthma, asthma flare-ups are likely to come on quickly and can be very severe.

What causes brittle asthma?

See the main asthma leaflet for causes of asthma in general. Asthma symptoms are caused by swelling (inflammation) and narrowing of the airways in the lungs.

We don't know exactly what causes brittle asthma in some people, but it's probably down to a combination of things that differ from person to person. Some possibilities include:

• Allergies. Many people with brittle asthma have atopy, a condition where the immune system tends to react strongly to allergenic things in the environment, leading to allergies, asthma, and eczema. Allergies to dust mite and different types of food allergy, such as allergies to dairy products, have been reported in people with brittle asthma. Allergies to pets and other animals may also be present. So, exposure to allergic triggers might trigger severe asthma reactions in people who are sensitive to them.

• Vulnerability to infections. Infections are a common trigger for asthma, and there have been some suggestions that people with brittle asthma might be particularly vulnerable to developing infections of the throat, sinuses, airways, or lungs.

• Psychological factors. People with severe asthma, including brittle asthma, often experience major effects on their day-to-day life from asthma, which can affect their mental health. There is some evidence that poor mental health might affect people's ability to self-manage asthma symptoms; for example, one study found that people with brittle asthma were more likely to delay seeking medical help, and tended to try to avoid using steroid tablets as long as possible, which could be harmful. Like most conditions, asthma symptoms and mental health are closely interlinked, and both can affect each other.

• Awareness of symptoms. Research on people who have had near-fatal attacks of asthma has found that they sometimes have a reduced ability to feel the early signs of their asthma worsening. It's not really known why this happens. This might explain why a brittle asthma attack can seem to come on suddenly without apparent warning - but there might actually have been signs that weren't noticed.

• Smoking or vaping. Smoking any substance (tobacco, cannabis, crack cocaine, heroin, or anything else) worsens inflammation in the lungs and makes asthma worse. Vaping is less harmful than smoking, but still causes lung inflammation and can trigger asthma attacks.

• Obesity. Obesity makes asthma worse, and weight loss can help to improve asthma symptoms.

• Resistance to steroids. Inhaled steroids are a very good treatment for most people with asthma. In a small number of people, though, inhaled and oral (tablet) steroids seem to have much less of an effect on their asthma. The reasons for this are very complex and not fully understood.

What is the life expectancy with brittle asthma?

Severe asthma attacks can be life-threatening. In 2018, over 1,400 adults and children died from asthma in the UK. Most asthma deaths, though, are potentially preventable, such as by avoiding and reducing asthma triggers, getting the right treatments, and using them correctly and regularly.

People with severe asthma - which includes many people with brittle asthma - are more likely to have life-threatening attacks of asthma, and tend to require more courses of steroid tablets, which have many side effects. Sadly, both of these can lead to a reduced life expectancy.