Although asthma is a common disorder, it is difficult to define accurately, even for a physician. Using data from many sources, physicians know that the incidence of this condition is relatively high. Asthma affects nearly nine million people in the United States and causes an estimated four thousand deaths each year. It may also be an underlying cause of death in three to four times that number. Moreover, it isn’t evident from these figures that asthma causes considerable discomfort and inconvenience. Asthma may keep as many as thirty thousand working people from their jobs each day, not to mention the students kept home from school. Asthmatics frequently wind up in emergency rooms because of this disease or its complications. To the patient, asthma is a feeling of tightness in the chest, labored breathing, wheezing, coughing, gasping, and fatigue, with the apprehension that results. Although not all these symptoms may be present during a specific attack, the patient is always acutely aware that something uncomfortable and unpleasant is going on in his or her body. To the physician, asthma is a reversible, obstructive disease of the air passages that is caused by varying degrees of bronchial muscle spasm, a swelling of the mucosa, and an excessive amount of mucus. The bronchial muscles of an asthmatic twitch more than do the muscles of a normal person. This is evident in the bronchial obstruction that occurs after inhalation of small quantities of histamine, for example, or of another chemical substance that resembles acteylcholine, a substance normally released from certain nerve endings. Five points about the definition of asthma should be understood: 1. The term reversible is important to the patient. It means that, with the appropriate medication, the patient’s breathing condition will improve and eventually become normal. It is an optimistic outlook, since the physician need only find the right approach or combination of approaches and the patient can return to a relatively normal life. If lung damage has occurred, however, some effects of asthma may be irreversible. In such cases, patients will never be able to breathe as well as they once could. If this happens, the aim in treating asthmatics is to help them function as well as possible under the circumstances. It is sometimes difficult, however, to determine the extent to which a patient’s disease is reversible. Only after trying bronchodilators, and even long-term corticosteroids, can we properly assess the prospect of reversibility. 2. "Wheezing"—in the popular mind the most common symptom of asthma—is more often than not the doctor’s term, not the patient’s. Patients usually mention a feeling of tightness during an asthma attack. Coughing is another symptom that may occur, either alone in an individual not suspecting a diagnosis of asthma, or as part of an asthma attack. Some patients also experience a feeling of fatigue during an attack. 3. Many people, including some physicians, confuse asthma with allergy. Numerous asthma patients, in fact, do not have allergies, and many allergy patients do not have asthma. Perhaps this confusion has led patients to seek a magic cure for asthma by eliminating some allergic substance in the environment. Unfortunately, because asthma is a complex condition with many causes, people are rarely able to remove a single environmental substance and thus significantly alter their condition. Realistically, they should not expect a cure but rather seek a program of treatment adequate for controlling the symptoms of wheezing and one that will allow them to live fairly normal lives. 4. Some of the same misconceptions discussed in paragraph 3 have led to an incorrect or oversimplified definition of asthma, primarily because of the use of the adjectives extrinsic and intrinsic. These are outmoded terms that no longer indicate accurately the outcome of treatment. The term extrinsic asthma refers to people in whom allergies seem to be the most important causative factors. Skin tests are usually positive. The patient is often a child or young adult rather than someone who has developed asthma later in life. Such asthma attacks are thought to be related to such specific allergens as ragweed. Doctors now doubt that such a pure group exists since such factors as irritants and emotions may play as large a role in this allergic group as any other subgroup. It is rare for just a few environmental substances to be responsible for all the symptoms. That situation exists only among the mildest asthmatic patients, those that respond readily to treatment. At present, the term intrinsic asthma is used to refer to patients who are not allergic, whose asthma attacks do not stem from a known cause but are triggered by infection and nonspecific irritants. The word intrinsic, however, does not describe accurately a specific, known mechanism. This situation arises—in the case of bacteria, at least— because of the role of infection in provoking symptoms in asthmatic patients, a role that is uncertain. When these terms fit a patient’s condition very well, the word mixed is used. A "mixed asthmatic" patient is one whose symptoms are triggered by extrinsic factors and who has persistent problems with unknown causes. 5. What the allergist calls an intrinsic asthmatic, a chest physician might call chronic bronchitis. Chronic bronchitis is defined as a condition in which a cough with sputum is present for at least three months of the year and for at least two consecutive years. Many physicians, however, are not satisfied with this term. The amount of sputum can vary in an individual, and medications can greatly decrease the amount of sputum. Many "bronchitics" have irritable airways similar to those of asthmatic patients. Because reversibility is almost always present, treatment of these patients is usually no different from that of other asthmatics. Perhaps where bronchitics differ most is that many of them have a long history of smoking and thus less chance of reversibility.