What Is Asthma?
By Dr. Nyjon Eccles BSC MBBS PhD MRCP

Asthma is a condition that affects the airways – the small tubes that carry air in and out of the lungs. If you have asthma your airways are almost always sensitive and inflamed. When you come in to contact with something that you are allergic to, or something that irritates your airways (a trigger), your airways react by constricting due to the muscles around the walls of your airways tightening and thereby becoming narrower, making it harder to breathe. The lining of the airways becomes inflamed due to an auto-immune allergic reaction. The outcome is swelling and often the production of sticky mucus or phlegm. This combination leads to the experience of asthma symptoms. Asthma tops the list of chronic respiratory diseases found in children in Western societies today. Over 5.1 million people in the UK have asthma – that's around 1 in 13 adults.

A 1997 study published in Science reported that “the prevalence of asthma in westernized societies has risen steadily this century, doubling in the last 20 years. Asthma now affects one child in seven in Great Britain, and in the United States it causes one-third of pediatric emergency room visits.” Another study found that between 1964 and 1980, asthma in children aged six to 11 years increased 50 per cent. In 1995, the CDC reported that, between 1982 and 1992, asthma increased 52 per cent for persons between the ages of five and 34 years old, and deaths from asthma increased 42 per cent. The 1978 Canada Health Survey found that only 2.3 per cent of Canadians 15 years and over reported having asthma. By 1991, its prevalence was at 6 per cent. Now more than 1.5 million Canadians of all ages suffer from asthma. Asthma’s economic burden is formidable. Asthma costs UK £2 billion every year. In the U.S., the total cost of illness related to asthma in 1990 was estimated at $6.2 billion. According to Canada’s 1994 National Population Health Survey, the long-term disability costs associated with asthma, emphysema, and chronic bronchitis in 1993 totaled $1.8 billion, without counting costs associated with treating asthma in children under 11 years old. Although public health officials attribute the recorded increases in asthma to better case diagnoses, more air pollution indoors and outdoors, and smoking, some scientists find evidence that vaccination and lack of contagious infectious diseases in early childhood may later encourage the development of asthma and other allergic conditions.  
     
In 1996, the British medical journal, The Lancet, published Danish and British findings concerning child health, lung function, and allergy. Noting that the incidence of early childhood diseases in Britain had fallen this century while those of allergic diseases such as asthma, hay fever, and eczema rose sharply, the researchers hypothesized that certain childhood infections, specifically measles, may protect against allergy. A European Commission survey has reported that 13% of people over 15 in the UK have had asthma at some point in their lives. National Asthma Campaign experts say this matches their own statistic, which puts the number of Britons diagnosed with the condition at eight million. The UK figure was the highest in the survey of 16 European Union member states, with runners-up Finland (11%) and Ireland (10.5%) not far behind. Lowest in the table were Germany, with less than 4% of the population saying they had asthma, and Spain, with a total of 4.4%. The survey was carried out in January and February 2003, with an average of 1,000 participants over the age of 15 in each country answering questionnaires about a range of health issues. Eight million people in the UK have been diagnosed with asthma at some point in their lives. More than five million people in the UK are receiving treatment for asthma, and it is the UK's most common long-term childhood illness: one in eight children are currently being treated for asthma symptoms.

The UK has the highest rate of severe wheeze in the world for children aged 13 to 14. Asthma has become more common over the last 30 years, but we still do not know why this is. Scientists believe there may be many contributory factors, which are a result of our changing lifestyles. For example, we are more likely to have centrally heated homes with fitted carpets and little ventilation; ideal conditions for the house-dust mite, a very common asthma trigger that lives in soft furnishings. Our diets now include fewer fresh foods, while some evidence suggests that eating plenty of fruit and vegetables can help to reduce asthma symptoms. It has also been suggested that our increasingly clean environment is to blame for the rise in asthma. The so-called 'hygiene hypothesis' is based on evidence that shows exposure to bacteria at an early age can help to build immunity against developing allergies and asthma later in life.     
                                                               
What are asthma symptoms?

Asthma symptoms can vary. You may find that you start to cough or wheeze, get short of breath, or have a tight feeling in your chest. Despite what many people think, wheezing does not always occur. In fact, coughing is the most common asthma symptom. What are the causes of asthma? Asthma can start at any age. Some people get symptoms during childhood which then disappear in later life. Others develop 'late-onset' asthma in adulthood, without ever having had symptoms as a child.

It is difficult to say for sure what causes asthma, but so far we know that:

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