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What Exactly Is Asthma?

   Asthma is a common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, airflow obstruction, andbronchospasm. Symptoms include wheezing, cough, chest tightness, and shortness of breath .

Epidemiology :

Disability-adjusted life year for asthma per 100,000 inhabitants in 2004.
     no data     less than 100     100–150     150–200     200–250     250–300     300–350     350–400     400–450     450–500     500–550     550–600     more than 600

   A 1998 study of asthma prevalence worldwide found great disparities (as high as a 20 to 60-fold difference) in asthma across the world, with a trend toward more developed and westernized countries having higher rates of asthma. Westernization however does not explain the entire difference in asthma prevalence between countries, and the disparities may also be affected by differences in genetic, social and environmental risk factors. Mortality however is most common in low to middle income countries, well symptoms were most prevalent (as much as 20%) in the United Kingdom, Australia, New Zealand, and Republic of Ireland; they were lowest (as low as 2–3%) in Eastern Europe, Indonesia, Greece, Uzbekistan, India, and Ethiopia.

   Research suggests that the prevalence of childhood asthma has been increasing, and this increased prevalence is greater than that in adults. Some 9% of US children had asthma in 2001, compared with just 3.6% in 1980. The World Health Organization (WHO) reports that some 8% of the Swiss population suffers from asthma today, compared with just 2% some 25–30 years ago.

   While asthma is more common in affluent countries, it is by no means a restricted problem; the WHO estimate that there are between 15 and 20 million people with asthma in India. In the U.S., urban residents, Hispanics, and African Americans are affected more than the population as a whole. Striking increases in asthma prevalence have been observed in populations migrating from a rural environment to an urban one, or from a third-world country to Westernized one.

   In 2005 in the United States asthma affected more than 22 million people including 6 million children. It accounted for nearly 1/2 million hospitalizations, and 14 million missed days of school annually. More boys have asthma than girls, but more women have it than men.Of all children, African Americans and Latinos who live in cities are more at risk for developing asthma. African American children in the U.S. are four times more likely to die of asthma and three times more likely to be hospitalized, compared to their white counterparts. In some Latino neighborhoods, as many as one in three children has been found to have asthma.

   In England, an estimated 261,400 people were newly diagnosed with asthma in 2005; 5.7 million people had an asthma diagnosis and were prescribed 32.6 million asthma-related prescriptions.

Signs & symptoms :

   Because of the spectrum of severity within the asthma, some people with asthma only rarely experience symptoms, usually in response to triggers, where as other more severe cases may have marked airflow obstruction at all times.
   Asthma exists in two states: the steady-state of chronic asthma, and the acute state of an acute asthma exacerbation. The symptoms are different depending on what state the patient is in.
   Common symptoms of asthma in a steady-state include: nighttime coughing, shortness of breath with exertion but no dyspnea at rest, a chronic 'throat-clearing' type cough, and complaints of a tight feeling in the chest. Severity often correlates to an increase in symptoms. Symptoms can worsen gradually and rather insidiously, up to the point of an acute exacerbation of asthma. It is a common misconception that all people with asthma wheeze—some never wheeze, and their disease may be confused with another chronic obstructive pulmonary disease such as emphysema or chronic bronchitis.

Causes of asthma :

Asthma is caused by environmental and genetic factors, which can influence how severe asthma is and how well it responds to medication. Some environmental and genetic factors have been confirmed by further research, while others have not been. Underlying both environmental and genetic factors is the role of the upper airway in recognizing the perceived dangers and protecting the more vulnerable lungs by shutting down the airway.

- Environmental factors : There are several environmental factors are playing their role in asthma . Important factors are low air quality , high ozone levels , traffic pollution , environmental tobacco smoke , viral respiratory infections , psychological stress etc .

- Genetic factors : Over 100 genes have been associated with asthma in at least one genetic association study. However, such studies must be repeated to ensure the findings are not due to chance. Through the end of 2005, 25 genes had been associated with asthma in six or more separate populations - GSTM1 ,IL10 ,CTLA-4 ,SPINK5 ,LTC4S ,LTA ,GRPA ,NOD1 ,CC16 ,GSTP1 ,STAT6 ,NOS1 ,CCL5 ,TBXA2R, TGFB1 ,IL4 ,IL13 ,CD14 ,ADRB2 (β-2 adrenergic receptor) ,HLA-DRB1 ,HLA-DQB1 ,TNF ,FCER1B ,IL4R, ADAM33 .

- Gene-Environment interactions .

- Exacerbations .

Pathophysiology of asthma :

      Asthma is an airway disease that can be classified physiologically as a variable and partially reversible obstruction to air flow, andpathologically with overdeveloped mucus glands, airway thickening due to scarring and inflammation, and bronchoconstriction, the narrowing of the airways in the lungs due to the tightening of surrounding smooth muscle. Bronchial inflammation also causes narrowing due to edema and swelling caused by an immune response to allergens.

     There are several stimulli working behind the disease . They are - 

  1. Allergens from nature, typically inhaled, which include waste from common household pests, the house dust mite and cockroach, as well as grass pollen, mold spores, and petepithelial cells.
  2. Indoor air pollution from volatile organic compounds, including perfumes and perfumed products. Examples include soap, dishwashing liquid, laundry detergent, fabric softener, paper tissues, paper towels, toilet paper, shampoo, hairspray, hair gel, cosmetics, facial cream, sun cream, deodorant, cologne, shaving cream, aftershave lotion, air freshener and candles, and products such as oil-based paint.
  3. Medications, including aspirin, β-adrenergic antagonists (beta blockers), and penicillin.
  4. Food allergies such as milk, peanuts, and eggs. However, asthma is rarely the only symptom, and not all people with food or other allergies have asthma 
  5. Sulfite sensitivity Asthma can occur in reaction to ingestion or inhalation of sulfites, which are added to foods and wine as preservatives.
  6. Salicylate sensitivity Salicylates can trigger asthma in sensitive individuals. Salicylates occur naturally in many healthy foods. Aspirin is also a salicylate.
  7. Use of fossil fuel related allergenic air pollution, such as ozone, smog, summer smog, nitrogen dioxide, and sulfur dioxide, which is thought to be one of the major reasons for the high prevalence of asthma in urban areas.
  8. Various industrial compounds (e.g. toluene diisocyanate ) and other chemicals, notably sulfites; chlorinated swimming pools generate chloramines—monochloramine (NH2Cl), dichloramine (NHCl2) and trichloramine (NCl3)—in the air around them, which are known to induce asthma.
  9. Early childhood infections, especially viral upper respiratory tract infections. Children who suffer from frequent respiratory infections prior to the age of six are at higher risk of developing asthma, particularly if they have a parent with the condition. However, persons of any age can have asthma triggered by colds and other respiratory infections even though their normal stimuli might be from another category (e.g. pollen) and absent at the time of infection. In many cases, significant asthma may not even occur until the respiratory infection is in its waning stage, and the person is seemingly improving. In children, the most common triggers are viral illnesses such as those that cause the common cold.
  10. Exercise or intense use of respiratory system—the effects of which differ somewhat from those of the other triggers, since they are brief. They are thought to be primarily in response to the exposure of the airway epithelium to cold, dry air.
  11. Hormonal changes in adolescent girls and adult women associated with their menstrual cycle can lead to a worsening of asthma. Some women also experience a worsening of their asthma during pregnancy whereas others find no significant changes, and in other women their asthma improves during their pregnancy.
  12. Psychological stress. There is growing evidence that psychological stress is a trigger. It can modulate the immune system, causing an increased inflammatory response to allergens and pollutants.
  13. Cold weather can make it harder for patients to breathe. Whether high altitude helps or worsens asthma is debatable and may vary from person to person.
Management/Treatment :

   A specific, customized plan for proactively monitoring and managing symptoms should be created. Someone who has asthma should understand the importance of reducing exposure to allergens, testing to assess the severity of symptoms, and the usage of medications. The treatment plan should be written down and adjusted according to changes in symptoms.

   The most effective treatment for asthma is identifying triggers, such as cigarette smoke, pets, or aspirin, and eliminating exposure to them. If trigger avoidance is insufficient, medical treatment is recommended. Medical treatments used depends on the severity of illness and the frequency of symptoms. Specific medications for asthma are broadly classified in to fast acting and long acting.

   Bronchodilators are recommended for short-term relief of symptoms. For occasional attacks, no other medication is needed. If mild persistent disease is present (more than two attacks a week), low-dose inhaled glucocorticoids or alternatively, an oral leukotriene modifier or a mast-cell stabilizer. For those who suffer daily attacks, a higher dose of glucocorticoid is used. In a severe asthma exacerbation, oral glucocorticoids are added to these treatments.

Prognosis :

   The prognosis for asthma is good, especially for children with mild disease. Of asthma diagnosed during childhood, 54% of cases will no longer carry the diagnosis after a decade. The extent of permanent lung damage in people with asthma is unclear. Airway remodelling is observed, but it is unknown whether these represent harmful or beneficial changes. Although conclusions from studies are mixed, most studies show that early treatment with glucocorticoids prevents or ameliorates decline in lung function as measured by several parameters.For those who continue to suffer from mild symptoms, corticosteroids can help most to live their lives with few disabilities. It is more likely to consider immediate medication of inhaled corticosteroids as soon as asthma attacks occur. According to studies conducted, patients with relatively mild asthma who have received inhaled corticosteroids within 12 months of their first asthma symptoms achieved good functional control of asthma after 10 years of individualized therapy as compared to patients who received this medication after 2 years (or more) from their first attacks. Though they (delayed) also had good functional control of asthma,they were observed to exhibited slightly less optimal disease control and more signs of airway inflammation.
   Asthma mortality has decreased over the last few decades due to better recognition and improvement in care .

References :

1. wikimedia

2. wikipedia


© 2019 by Partha Sarathi(Director)