Types of asthma

Asthma isn’t really a single disease. It’s an umbrella term, covering various patterns of symptoms and a multitude of causes. This chapter looks at some of the common types of asthma, which may overlap. You should discuss your particular pattern of symptoms with your doctor or asthma nurse to help optimize your treatment. For example, from time to time most people with asthma experience symptoms when they exercise particularly heavily or during the occasional night. However, regularly suffering exercise-induced and nocturnal symptoms may indicate that your asthma is poorly controlled and so your dose of anti-inflammatory (preventer) might need to rise. On the other hand, some people experience symptoms only following exercise or during the night. As we’ll see, treatment may differ in each case.

Severe asthma

Between 5 and 10 per cent of asthmatics suffer severe symptoms – that’s around half a million British people, according to Asthma UK. While definitions vary, essentially severe symptoms remain poorly controlled despite repeated courses of standard drugs (usually including high doses of inhaled corticosteroid and oral steroids) and despite people sticking to their treatment.

Severe asthma can take several forms. Some people suffer asthma symptoms almost continually, despite taking steroids and other anti-inflammatory medications. Other patients with ‘brittle asthma’ endure severe attacks but have normal lung function and don’t experience marked symptoms in between. Others endure mild asthma that occasionally flares into a severe attack, despite taking their medication. Several factors can contribute to severe asthma:

  • Continual or repeated exposure to an allergen (such as house dust mite, cockroach or some fungi such as Alternaria) can lead to severe asthma.
  • Airway remodelling can also contribute to severe asthma, in which case symptoms usually worsen gradually, often over several years. (Nevertheless, some adults show a relatively rapid decline in lung function over ten years or less, especially if they developed asthma for the first time aged over 60 years.)
  • Asthma that persists from childhood tends to be more severe than asthma that first emerges in adults. For instance, Ségala and colleagues found that 31 per cent of adult asthmatics reporting no childhood asthma experienced less than one attack per month. In contrast, just 15 per cent of patients who recalled having asthma as a child suffered less than one exacerbation a month.
  • Respiratory infections – such as the bacteria Mycoplasma pneumoniae and Chlamydophila pneumoniae – commonly trigger severe asthma in adults.
  • More than 80 per cent of people with severe asthma have sinusitis: inflammation of the sinuses in the face (see page 39). It’s not clear whether sinusitis causes severe asthma, whether sinusitis and asthma arise from the same underlying inflammation, or both.
  • Smoking increases the frequency and severity of symptoms and exacerbations, and hastens the decline in lung function. So do all you can to quit. However, severe asthma also develops in lifelong non-smokers.
  • Around three-quarters of people with severe asthma are overweight or obese.

As this diversity suggests, you and your doctor will need to examine the details of your management, asthma patterns and lifestyle to determine your most appropriate treatment.

Recalcitrant asthma

Often doctors and patients lump recalcitrant and severe asthma together. However, they’re different: ‘recalcitrant asthma’ refers to symptoms that fail to respond adequately to treatment. As you may expect, many people with recalcitrant asthma suffer severe symptoms. However, mild symptoms might not respond fully to treatment, while some cases of severe life-threatening asthma improve quickly once treatment begins.

Recalcitrant asthma arises from several causes:

  • The doctor may misdiagnose asthma. Several diseases – such as COPD, congestive heart failure and vocal cord dysfunction – can mimic asthma’s symptoms. Treatments for asthma often aren’t effective in these other conditions. Indeed, they can make matters worse. Unfortunately, diagnosing asthma can prove especially difficult in older people or those with more than one ailment. So, if your asthma treatment doesn’t seem to be working, you could ask your doctor to investigate whether another condition could be responsible.
  • Recalcitrant symptoms can emerge if you and your doctor don’t adequately control a factor that increases asthma severity – such as indoor allergens, smoking, sinusitis or gastro-oesophageal reflux disease (GORD). People with GORD regurgitate small amounts of stomach acid into their mouth. Some of this can seep into the trachea and lungs, exacerbating the severity of their asthma. Tackling any exacerbating factors can enhance the response to anti-asthma medicines.
  • Doctors and asthma nurses don’t always treat asthma aggressively enough. Some doctors may, for example, not increase the steroid dose or suggest an additional treatment because they worry about side effects. (The principle ‘first do no harm’ is one of medicine’s most important ethical and intellectual foundations.) There are now guidelines for asthma control, which offer doctors clear advice on when to increase treatment and the most appropriate drug.
  • Patients fail to take their medication as advised by the doctor or asthma nurse – so-called poor ‘compliance’, ‘adherence’ or ‘concordance’. Some people may deliberately not take their medicines because they feel they don’t need the drug or because they worry about side effects. This article, and a full and frank discussion of the risks and benefits with your GP or asthma nurse, should resolve concerns about the efficacy or safety of your treatment.
  • Remodelling and other severe complications of asthma can lead to recalcitrant symptoms as the obstruction becomes ‘fixed’ and less responsive to treatment. Alternatively, the inflammation may simply be too severe for steroids to tackle effectively.
  • Some people show a markedly impaired response to steroids, the mainstay of treatment for asthmatic inflammation. As Adcock and Barnes note, researchers are only beginning to unravel the complex causes of steroid resistance. However, some people (perhaps because of their genetic code) produce too few or insensitive steroid receptors (receptors bind the steroid, which starts a chain of events that ends with the anti-inflammatory action). In other cases, the chain of events inside the cell through which steroids reduce inflammation seems to be dysfunctional.

Fortunately, research is beginning to yield new treatments for severe asthma. For example, omalizumab offers an option for adults and adolescents with severe, persistent and unstable allergic asthma.

Nocturnal asthma: a wake-up call

Among other important actions, sleep helps consolidate memories and learning, protected our ancestors from attack by predators, and aids mental and physical recuperation. Given its biological importance, it’s not surprising that sleep disturbances potentially cause considerable distress. However, according to a survey carried out by Asthma UK, 61 per cent of asthmatics say that respiratory symptoms stop them from getting a good night’s sleep, which can leave the person tired, irritable and sleepy the next day. Tired people are also more likely to have accidents and their performance at work or college can suffer.

As the survey shows, around 60 per cent of people with asthma find that wheezing and other symptoms are worse at night and in the early morning – so-called nocturnal asthma. Some people experience symptoms only at night. Three main changes contribute to this pattern:

  • Nocturnal asthma symptoms reflect the natural variation in the diameter of the bronchi over the course of the day. Even in healthy people, changes in the airway diameter mean that lung function peaks around 4 p.m. and reaches a nadir around 4 a.m. However, the difference between peak and trough lung function is much greater in asthma patients than in people with healthy lungs.
  • Inflammation seems to worsen during the night in people with nocturnal asthma more than in people with asthma of similar severity who do not wake at night wheezing or breathless. For example, levels of some mediators produced by the body to bolster or reduce inflammation vary over the course of the day.
  • Many people with asthma experience their most severe chest tightness and wheezing when they get up in the morning. This seems to reflect the combination of narrow bronchi, increased physical activity and worse inflammation.

Nocturnal asthma remains under-diagnosed, partly because some asthmatics feel that the disturbed nights are an inevitable part of the disease. Other people seem to feel that changes in sleep patterns are part of ageing. Certainly, around half of elderly people report insomnia and poor sleep quality. Nevertheless, you should not dismiss a disturbed night’s sleep as simply part of growing older. Nocturnal symptoms should be a wake-up call for you to see your doctor or asthma nurse. Waking at night wheezing or breathless is one of the strongest indicators that your asthma is poorly controlled.

Exercise-induced asthma

Healers knew that exercise could induce asthma more than 1,800 years ago. Today, doctors recognize that exercise can trigger symptoms in 80 to 90 per cent of people with asthma. Some people experience asthma symptoms only when they exercise. Nevertheless, exercise-induced symptoms are not an excuse to become a couch potato. Indeed, Sinha and David note, 29 per cent of elite athletes show exercise-induced bronchoconstriction. Furthermore, exercise helps alleviate asthma (by improving lung function) and helps counter some other risk factors linked to the disease, such as obesity.

Elaine’s exercise-induced asthma

Her school asked Elaine, a 28-year-old teaching assistant, to help with the netball club and PE classes. She’d not really exercised since leaving school but agreed, especially as it would help her lose the extra weight she’d put on since giving birth to her daughter four years before. However, about ten minutes into the class, breathlessness forced Elaine to the sidelines. Elaine thought she was just unfit. But every time she took part or tried to jog around the park to boost her fitness, she had to stop every five or ten minutes to catch her breath, and kept coughing and wheezing. She didn’t smoke and wondered if she was anaemic. But her doctor suspected exercise-induced asthma. Taking a short-acting bronchodilator 15 minutes before exercise allowed Elaine to take an active part in the class and club. She’s been jogging regularly and is training towards taking part in the local half-marathon to raise funds for the school.

So why do some people experience exercise-related bronchoconstriction? When you exercise, your muscles demand more oxygen. In response, your heart beats more quickly, your respiration rate rises and your bronchi dilate to let more air into the lungs. In healthy people, bronchi remain open throughout exercise. But in people with exercise-induced asthma, the drier and cooler air you inhale during exercise triggers the bronchi to narrow, usually between five and 15 minutes after you start working out.

As your respiration rate rises, you are less able to humidify and warm the increased amount of air you breathe in. In sensitive patients, especially in people with pre-existing inflammation, increased evaporation of water from the lungs triggers the release of mediators from mast cells (including histamine and leukotrienes). The resulting bronchoconstriction can cause chest pain, breathlessness, cough and wheeze during or after exercise. Cold air increases the dehydration and exacerbates the airway narrowing.

So you may have exercise-induced bronchospasm if you experience one or more of the following between five and 15 minutes after starting to work out:

  • Shortness of breath or chest tightness.
  • You find your exercise endurance unexpectedly declines or doesn’t improve when you increase your workouts.
  • You cough or wheeze.

Some patients with exercise-induced asthma also suffer upset stomachs or a sore throat.

The timing of symptoms is critical. Symptoms that emerge during the first five minutes of a workout do not usually indicate exercise-induced asthma, but may indicate poorly controlled asthma, lack of fitness or injury to the muscles in your chest wall. So see your doctor, who may suggest that you take an exercise tolerance test, for example, to differentiate wheezing due to asthma from other causes of shortness of breath on exertion. Heart failure, severe anaemia and obesity, which are often exacerbated by poor physical fitness, can all cause shortness of breath during exercise.

It’s worth making the effort to identify the cause and to get fit. Ironically, physical fitness is one of the best ways to beat exercise-induced bronchoconstriction. As your physical fitness improves, you use less of your vital capacity to exercise at any particular level of activity. Fitness also reduces the cooling and drying effect of air, and therefore the severity of bronchoconstriction triggered by exercise. The section below offers some suggestions that should reduce the risk of suffering symptoms while you work out. In other words, there is no excuse not to exercise! After all, 67 athletes at the 1984 Olympic Games suffered from asthma. So talk to your doctor or nurse first and pick up those trainers.

Preventing exercise-induced asthma

  • Increase your physical fitness. If you’re a member of a gym, ask them to review your programme. If not, think about joining.
  • Warm up for at least ten minutes before exercising.
  • Cover your mouth and nose with a scarf or mask when exercising in cold weather.
  • If possible, exercise in a warm environment with humidified air.
  • Avoid allergens and pollution – so don’t jog through the woods or fields, or exercise in front of an open window on a polluted city street.
  • At the end of exercise, cool down or gradually reduce the exercise intensity.
  • Wait at least two hours after eating before exercising.
  • Choose the right exercise. Running is more likely to trigger asthma than cycling, for instance. Both are more likely to induce asthma than swimming. As cold air is a common trigger, many people with asthma find ski-ing, skating and other winter sports trigger their symptoms.
  • Take a short-acting bronchodilator 15 minutes before and, if needed, during exercise. You could also try sodium cromoglicate and nedocromil, which prevent exercise-induced symptoms in between 70 and 85 per cent of patients. You can discuss these options with your doctor or asthma nurse.

Drug-induced asthma

Every time you take aspirin or ibuprofen, you’re part of a medical tradition stretching back thousands of years. Plants evolved a chemical called salicylic acid as part of their defences against disease. But our ancestors soon learnt that consuming a preparation of plants containing salicylates alleviated pain, inflammation and fever. For example, the Ebers Papyrus, an Egyptian text written some 3,500 years ago, suggests using herbal painkillers that we now know contain salicylates. Greek and Roman healers employed salicylate-containing plants to alleviate rheumatism. Traditional British healers used willow bark, which is rich in salicylic acid, to relieve pain and fever. In 1763, Edward Stone, a vicar in the Oxfordshire village of Chipping Norton, found that a dram (about 1.8 g) of willow bark extract alleviated fever.

German scientists synthesized salicylic acid chemically in 1860. A chemical variation, acetylsalicylic acid, followed in 1899, and was marketed as Aspirin. Today, the chemical offspring of natural salicylates and acetylsalicylic acid – a group of drugs called non-steroidal anti-inflammatory drugs (NSAIDs), which includes ibuprofen, diclofenac and naproxen – are among the most widely prescribed medicines.

Yet familiarity shouldn’t breed complacency. NSAIDs can cause serious, even life-threatening side effects, including gastrointestinal ulcers and bleeding (haemorrhage), strokes and asthma. Indeed, aspirin may precipitate an attack in up to a fifth of people with asthma. Kuna and colleagues report the case of a 48-year-old Polish man who was so sensitive to aspirin that he suffered an attack following sexual intercourse with his wife after she’d taken aspirin – although only when he didn’t use a condom.

So people with asthma should not use NSAIDs – even creams or gels, and even if bought without a prescription (over the counter) from a pharmacy or supermarket – without speaking to a doctor, pharmacist or nurse first. The risk of developing asthma symptoms rises as the NSAID dose increases. Therefore, even if the health professional agrees, make sure you follow the dosing instructions, take the minimum amount that controls your pain or inflammation, and use the medicine for the shortest time you can. If you develop a rash or suffer physical side effects such as difficulty breathing, dyspepsia (indigestion) or abdominal pain, stop using the NSAID and seek medical advice as soon as possible.

You should always tell pharmacists that you suffer from asthma and let them know what other medications you are taking – including herbal treatments – when buying an over-the-counter painkiller or flu remedy. Pharmacists can offer you alternatives (such as paracetamol). Asthmatics also need to be careful of some herbal medicines. As we’ve seen, many plants contain salicylates. So make sure that the herbalist knows you suffer from asthma (even if you’re not consulting for respiratory symptoms). And your doctor, nurse and pharmacist should know if you’re taking herbal supplements.

Other medicines that can trigger asthma

Several other medicines potentially trigger asthma in sensitive people. For example, doctors prescribe drugs called beta-blockers for, among other conditions, some cases of dangerously high blood pressure (hypertension), some anxiety symptoms and glaucoma. (In glaucoma, pressure exerted by fluids inside the eye damages the nerves carrying signals from the light-sensitive retina at the back of the eye to the brain. Untreated glaucoma can lead to blindness.)

Beta-blockers cause airways to narrow. In healthy people taking beta-blockers, the narrowing isn’t enough to cause respiratory symptoms. However, in people with asthma the narrowing may provoke an attack. Enough beta-blocker can even reach the bloodstream from eye drops used to treat glaucoma to trigger bronchoconstriction. Fortunately, doctors can usually find an alternative medication that will not provoke exacerbations.

Rory and the hot dog

Rory, a 31-year-old sales executive, has suffered from asthma since childhood. And he knows that aspirin makes his asthma worse. So he carefully avoids taking NSAIDs, always reads the side of the box of any painkiller or cold and flu remedy he buys, and tells the pharmacist about his aspirin sensitivity. However, at a recent football match he suffered a severe asthma attack that left him wheezing and breathless during the second half of the important game. He assumed the excitement was responsible – ‘Just my luck,’ he lamented to his friends. But the attack happened again at another game, and then at his children’s school fireworks display. He realized that on all three occasions he’d eaten hot dogs. At his next routine appointment, he asked – rather hesitantly – whether he could be allergic to hot dogs. The nurse mentioned that some hot dogs contain preservatives or a colour that might trigger his aspirin-sensitive asthma. Rory now sticks to burgers.

Food additives

Food manufacturers may use salicylates as preservatives in certain foods, including some hot dogs, ice cream, sandwich spreads, soft drinks and so on. A wide range of other preservatives as well as several colours and antioxidants can trigger asthma in sensitive people. For example, the yellow dye tartrazine triggers symptoms in around half of people with aspirin-sensitive asthma. (These are not allergies: IgE isn’t involved.)

Salicylates also occur naturally in some fruits and vegetables. So totally avoiding salicylates is impracticable. But if you are sensitive, try to avoid those foods that seem to evoke a strong reaction – and always read the label. (You may need to keep a food diary to discover any foods that provoke symptoms in you.) Table 1 below shows some common additives associated with asthma in sensitive people.

Table 1: Examples of additives that may provoke asthma symptoms in some sensitive people

  • E102 Tartrazine
  • E104 Quinoline yellow
  • E110 Sunset yellow
  • E122 Carmoisine
  • E123 Amaranth
  • E132 Indigo carmine
  • E142 Green S
  • E160b Annatto
  • E210–219 Benzoates
  • E223 Sodium metabisulphite
  • E320 Butylated hydroxyanisole (BHA)
  • E321 Butylated hydroxytoluene (BHT)