Severe Asthma in Children Raises Risk of Adult COPD

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Scientists have revealed yet another reason to be concerned about the continuing rise in the prevalence of asthma among children. Results of a study from the Royal Children’s Hospital in Melbourne note that children who have severe asthma have a more than 30 times greater risk of developing chronic obstructive pulmonary disease (COPD) as adults.

Asthma among children has been on the rise for decades. Between 1980 and 1994, there was a greater than 160 percent increase in asthma rates in children younger than five years old, according to the Centers for Disease Control and Prevention. The National Center for Health Statistics reported that 8.9 percent of US children had asthma in 2005, and by 2007, a report from the American Lung Association noted that nearly 10 percent of school-age children had asthma.

Several factors are believed to be contributing to this increase. Environmental triggers, including poor air quality, climate change, and exposure to second hand smoke recently have been reported to be significant culprits. Indoor pollutants are also named, including nitrogen dioxide, exposure to mice and cockroaches, and other allergens.

In the new Melbourne study, the lead author, Andrew Tai, MBBS, FRACP, noted that he and his team set out “to describe the association between the pattern of childhood asthma and the risk of developing adult COPD in a longitudinal cohort.” Their subjects were from the Melbourne Asthma Study, who had been recruited at age seven in 1957. At enrollment, the children were classified into four groups: free of wheeze, presence of intermittent asthma, presence of persistent asthma, or severe asthma. All the participants were evaluated regularly until they reached age 50.

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A total of 197 people from the original group responded to a comprehensive questionnaire and underwent lung function tests for the current study. Individuals who had been diagnosed with severe asthma as children had a 31.9 times greater risk of having COPD as adults than children who did not have asthma.

The authors noted that children who had experienced mild asthma were not at increased risk of developing COPD as adults. Tai explained that most children with mild asthma usually grow out of the condition by adolescence or adulthood, while those who had more severe asthma “tend to have predisposing risk factors (like atophy) and continue to have symptoms of wheeze well into adult life.”

The researchers also pointed out that they believe the children who had severe asthma initially had poorer baseline lung function than did other less severe cases, and that their lung function gradually worsened over time until they reached a level characteristic with a diagnosis of COPD.

The two main conditions associated with COPD are chronic bronchitis and emphysema. The CDC reports (2008 figures) that 9.8 million adults were diagnosed with chronic bronchitis and 3.8 million adults were diagnosed with emphysema within the past year. COPD causes coughing accompanied by large amounts of mucus, wheezing, shortness of breath, chest tightness, and other symptoms. Although cigarette smoking is the leading cause of COPD, exposure to lung irritants such as air pollutions and dust may also contribute to this disease.

For now, researchers do not completely understand what links severe childhood asthma with adult COPD, but the authors of this study believe that “early treatment to prevent airway remodeling in childhood may reduce the incidence of this long-term complication of childhood asthma,” said Tai. Results of this study were presented at the American Thoracic Society International Conference in New Orleans on Sunday, May 16.

SOURCES:
Akinbami LJ. The state of childhood asthma, US, 1980-2005. National Center for Health Statistics, 2006.
American Academy of Allergy Asthma and Immunology
American Lung Association, Trends in Asthma Morbidity and Mortality November 2007
American Thoracic Society
Centers for Disease Control, Surveillance for Asthma—US 1960-1995 MMWR 1998

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