Asthma DEFINITION Asthma is a syndrome characterized by

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Asthma

Asthma

DEFINITION �Asthma is a syndrome characterized by airflow obstruction that varies markedly, both spontaneously

DEFINITION �Asthma is a syndrome characterized by airflow obstruction that varies markedly, both spontaneously and with treatment

PREVALENCE � Asthma is one of the most common chronic diseases globally and currently

PREVALENCE � Asthma is one of the most common chronic diseases globally and currently affects approximately 300 million people worldwide

World map of prevalence of asthma

World map of prevalence of asthma

� The prevalence of asthma has risen in affluent countries over the last 30

� The prevalence of asthma has risen in affluent countries over the last 30 years but now appears to have stabilized � approximately 10– 12% of adults and 15% of children affected by the disease

� Asthma can present at any age, with a peak age of 3 years

� Asthma can present at any age, with a peak age of 3 years � In childhood, twice as many males as females are asthmatic, but by adulthood the sex ratio has equalized

� The severity of asthma does not vary significantly within a given patient �

� The severity of asthma does not vary significantly within a given patient � those with mild asthma rarely progress to more severe disease � those with severe asthma usually have severe disease at the onset

RISK FACTORS � Asthma is a heterogeneous disease with interplay between genetic and environmental

RISK FACTORS � Asthma is a heterogeneous disease with interplay between genetic and environmental factors

Endogenous Factors � Genetic � Atopy � Airway � Gender predisposition hyperresponsiveness � Ethnicity

Endogenous Factors � Genetic � Atopy � Airway � Gender predisposition hyperresponsiveness � Ethnicity � Obesity � Early viral infections

Environmental Factors � Indoor allergens � Outdoor allergens � Occupational sensitizers � Passive smoking

Environmental Factors � Indoor allergens � Outdoor allergens � Occupational sensitizers � Passive smoking � Respiratory infections � Diet � Acetaminophen (paracetamol)

Atopy � The strongest risk factor for asthma is a family history of atopy

Atopy � The strongest risk factor for asthma is a family history of atopy � Patients with asthma commonly suffer from other atopic diseases, particularly allergic rhinitis, which may be found in over 80% of asthmatic patients, and atopic dermatitis (eczema) � Atopy may be found in 40– 50% of the population in affluent countries

Genetic Predisposition � It now seems likely that different genes may also contribute to

Genetic Predisposition � It now seems likely that different genes may also contribute to asthma specifically, and there is increasing evidence that the severity of asthma is also genetically determined � asthma is polygenic � Genetic polymorphisms may also be important in determining the response to asthma therapy

Infections � Although viral infections (especially rhinovirus) are common triggers of asthma exacerbations, it

Infections � Although viral infections (especially rhinovirus) are common triggers of asthma exacerbations, it is uncertain whether they play a role in etiology � There is some association between respiratory syncytial virus infection in infancy and the development of asthma

Diet � The role of dietary factors is controversial � diets low in antioxidants

Diet � The role of dietary factors is controversial � diets low in antioxidants such as vitamin C and vitamin A, magnesium, selenium, and omega-3 polyunsaturated fats (fish oil) or high in sodium and omega-6 polyunsaturated fats are associated with an increased risk of asthma � Vitamin D deficiency may also predispose to the development of asthma

Obesity � an independent risk factor for asthma, particularly in women � the mechanisms

Obesity � an independent risk factor for asthma, particularly in women � the mechanisms are thus far unknown � Asthma occurs more frequently in obese people (body mass index >30 kg/m 2) and is often more difficult to control

Air Pollution � Air pollutants, such as sulfur dioxide, ozone, and diesel particulates, may

Air Pollution � Air pollutants, such as sulfur dioxide, ozone, and diesel particulates, may trigger asthma symptoms, but the role of different air pollutants in the etiology of the disease is much less certain � Indoor air pollution may be more important with exposure to nitrogen oxides from cooking stoves and exposure to passive cigarette smoke

Allergens � Inhaled allergens are common triggers of asthma symptoms

Allergens � Inhaled allergens are common triggers of asthma symptoms

Occupational Exposure � Occupational asthma is relatively common and may affect up to 10%

Occupational Exposure � Occupational asthma is relatively common and may affect up to 10% of young adults � Over 300 sensitizing agents have been identified

Triggers � Allergens � Upper respiratory tract viral infections � Exercise and hyperventilation �

Triggers � Allergens � Upper respiratory tract viral infections � Exercise and hyperventilation � Cold air � Sulfur dioxide and irritant gases � Drugs (β blockers, aspirin) � Stress � Irritants (household sprays, paint fumes)

Pharmacologic agents � All β blockers need to be avoided, and even selective β

Pharmacologic agents � All β blockers need to be avoided, and even selective β 2 blockers or topical application (e. g. , timolol eye drops) may be dangerous � Angiotensin-converting enzyme inhibitors are theoretically detrimental as they inhibit breakdown of kinins, which are bronchoconstrictors; however, they rarely worsen asthma � characteristic cough is no more frequent in asthmatics than in nonasthmatics

Exercise � Exercise is a common trigger of asthma, particularly in children � EIA

Exercise � Exercise is a common trigger of asthma, particularly in children � EIA is worse in cold, dry climates than in hot, humid conditions

Physical factors � Cold air � Hyperventilation � Laughter � strong smells or perfumes

Physical factors � Cold air � Hyperventilation � Laughter � strong smells or perfumes

Food and diet � There is little evidence that allergic reactions to food lead

Food and diet � There is little evidence that allergic reactions to food lead to increased asthma symptoms, despite the belief of many patients � Certain food additives may trigger asthma � Metabisulfite � Tartrazine

Air pollution � sulfur dioxide, ozone, and nitrogen oxides are associated with increased asthma

Air pollution � sulfur dioxide, ozone, and nitrogen oxides are associated with increased asthma symptoms

Hormones � Some women show premenstrual worsening of asthma, which can occasionally be very

Hormones � Some women show premenstrual worsening of asthma, which can occasionally be very severe � Thyrotoxicosis and hypothyroidism can both worsen asthma

Gastroesophageal reflux � Gastroesophageal reflux is common � acid reflux might trigger reflex bronchoconstriction

Gastroesophageal reflux � Gastroesophageal reflux is common � acid reflux might trigger reflex bronchoconstriction � it rarely cause asthma symptoms � antireflux therapy usually fails to reduce asthma symptoms in most patients

Stress � Psychological factors can induce bronchoconstriction through cholinergic reflex pathways

Stress � Psychological factors can induce bronchoconstriction through cholinergic reflex pathways