Prevalence and Incidence of Asthma

Prevalence/Incidence of Asthma: Online Medical Books

16 MEDICAL BOOKS ONLINE! Review excerpts from medical books online, free, without registration, for more information about the prevalence and/or incidence of Asthma.

Asthma: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

Asthma that results from sensitivity to specific external allergens is known as extrinsic. In cases in which the allergen isn’t obvious, asthma is referred to as intrinsic. Allergens that cause extrinsic asthma include pollen, animal dander, house dust or mold, kapok or feather pillows, food additives containing sulfites, and any other sensitizing substance. Extrinsic (atopic) asthma usually begins in childhood and is accompanied by other manifestations of atopy (type I, immunoglobulin [Ig] E-mediated allergy), such as eczema and allergic rhinitis. In intrinsic (nonatopic) asthma, no extrinsic allergen can be identified. Most cases are preceded by a severe respiratory infection. Irritants, emotional stress, fatigue, exposure to noxious fumes as well as changes in endocrine, temperature, and humidity may aggravate intrinsic asthma attacks. In many asthmatics, intrinsic and extrinsic asthma coexist.

Several drugs and chemicals may provoke an asthma attack without using the IgE pathway. Apparently, they trigger release of mast-cell mediators by way of prostaglandin inhibition. Examples of these substances include aspirin, various nonsteroidal anti-inflammatory drugs (such as indomethacin and mefenamic acid), and tartrazine, a yellow food dye. Exercise may also provoke an asthma attack. In exercise-induced asthma, bronchospasm may follow heat and moisture loss in the upper airways.

The allergic response has two phases. When the patient inhales an allergenic substance, sensitized IgE antibodies trigger mast-cell degranulation in the lung interstitium, releasing histamine, cytokines, prostaglandins, thromboxanes, leukotrienes, and eosinophil chemotaxic factors. Histamine then attaches to receptor sites in the larger bronchi, causing irritation, inflammation, and edema. In the late phase, inflammatory cells flow in. The influx of eosinophils provides additional inflammatory mediators and contributes to local injury.

Although this common condition can strike at any age, half of all cases first occur in children younger than age 10; in this age-group, asthma affects twice as many males as females. Nearly 1 in 13 children have asthma, which is increasing worldwide. Emergency department visits, hospitalizations, and mortality from asthma have been increasing for more than 20 years, especially among children and blacks.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Asthma: Asthma - epidemiology
(The 5-Minute Pediatric Consult)

Asthma - incidence

• Most common chronic illness in children
• Death from asthma in children more than tripled from 1979 to 1996, but has been decreasing since then, perhaps due to better recognition and increased use of anti-inflammatory medications. The incidence of death from asthma does not seem to correlate with severity.

Asthma - prevalence

• Wheezing in children is extremely common in the industrialized world (cumulative prevalence, 30–60%).
• In younger children, most episodes occur following viral infections.
• >50% of children who wheeze in early childhood stop wheezing by age 6 years.
• 14% of all young children (40% of those who wheeze during infancy) continue to wheeze.

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Source: The 5-Minute Pediatric Consult, 2008

About prevalence and incidence statistics:

The term 'prevalence' of Asthma usually refers to the estimated population of people who are managing Asthma at any given time. The term 'incidence' of Asthma refers to the annual diagnosis rate, or the number of new cases of Asthma diagnosed each year. Hence, these two statistics types can differ: a short-lived disease like flu can have high annual incidence but low prevalence, but a life-long disease like diabetes has a low annual incidence but high prevalence. For more information see about prevalence and incidence statistics.