Natural History of Asthma

Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at NSU

Natural History

Asthma is the most common chronic respiratory disease, affecting up to 10% of adults and 30% of children (JACI, 2011). Approximately 9% of the U.S. population has asthma - 9% of adult asthmatics have aspirin-exacerbated respiratory disease (AERD) (http://goo.gl/FIeE9).

It consists of recurrent episodes of:

- wheezing
- shortness of breath (SOB)
- chest tightness
- sleep disruption
- cough

Allergic Rhinitis and its Impact on Asthma (ARIA): Achievements in 10 years and future needs. ARIA has reclassified AR as mild/moderate-severe and intermittent/persistent. This classification closely reflects patients' needs and underlines the close relationship between rhinitis and asthma. http://buff.ly/QL1eYI

Symptoms are often worse at night or in the early morning.

Prevalence

1% in Ethiopia to over 20% in children Central and South America. The estimated total number asthma patients worldwide exceeds 150 million. Prevalence of asthma increased from 7.3% in 2001 to 8.2% (25 million) in 2009 - a 12.3% increase (CDC, 2011). U.S. asthma rates are rising but reasons are unclear, 25 million Americans, or 1 in 12 people, have asthma (Reuters, 2011). Asthma rate rises sharply in U.S.: 9.6% of children have asthma, and especially poor children, of whom 13.5% have it. In comparison, 7.7% of adults have asthma, the rate is higher among women (9.7%) and among poor adults of both sexes (10.6%) (NYTimes, 2011). One of the biggest jumps in asthma prevalence was in non-Hispanic black children - 17% had asthma in 2009 (WSJ, 2011).

From epidemiological perspective, asthma behaves as an epidemic, with rising prevalence over the past 30 years in all Westernized societies. The most striking increase has occurred in Australia, where 25% of children are diagnosed with asthma.

Childhood asthma is the number one cause of hospitalization, days lost from school, and childhood disability. The estimated cost of asthma in the U.S. was $ 11 billion in 1998.

Asthma impact in the U.S.:

- 4,000 deaths annually
- 500,000 hospitalizations annually
- 14.5 million missed days of school each year (the leading cause of school absenteeism)
- 14.5 million missed days of work for adults each year
- 1.9 million emergency room visits each year

The hygiene hypothesis

Decreased atopic sensitization associated with living in a farm was explored by studying bacteria found in cowsheds. Acinetobacter lwoffii and Lactococcus lactis shifted the immune response toward the secretion of TH1 cytokines in a murine model. One begins to wonder if biotherapy with bacterial extracts would be in the future of studies of allergy prevention.

There are several potential causes and factors for the increase in asthma:

- exposure to various allergens

- traffic exhaust fumes

- pesticides and certain plastics

- obesity and diet

Who will have asthma beyond childhood years?

Persistence of asthma beyond childhood depends on the type of asthma a particular child has.

- Mild wheezing at age 7 and younger, associated with URTI ---> 23% risk of persistence at age 35

- Definite diagnosis of asthma at age 7, not associated with URTI ---> 50% risk of persistence at age 35

- Severe asthma at age 20 ---> 75% risk of persistence at age 35

African American children living in poverty are at the highest risk of asthma. Asthma affects 5-10% of adults with prevalence decreasing to 4-8% in patients older than 65 years.

References

Allergy and Immunology MKSAP, 3rd edition.
Advances in basic and clinical immunology in 2007. Journal of Allergy and Clinical Immunology - Volume 122, Issue 1 (July 2008).

Audio

Asthma. Case Notes. BBC 4.

Related reading

"The Office" misinterprets the hygiene hypothesis (video) http://goo.gl/9YhwL

Published: 12/16/2007
Updated: 10/03/2012