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Child asthma linked to obesity

"We haven't quite understood the link between obesity and asthma. It is hard to determine which factor is the earlier cause."

Ou Liang-hsiu, pediatrician

Obesity may play a role in the increase in childhood and adolescent asthma, a study released by Chang Gung Children's Hospital yesterday said.

In a cohort study of ISAAC (International Study of Asthma and Allergy in Children), the Taiwanese research team collected 4882 questionnaires from children six years old, and 6381 from children 13 years old in Taipei City. The poll showed that the rate of childhood asthma has edged higher -- from 16.1 percent to 19.8 percent -- ?in the elementary school-age children in the past decade, while it has risen more sharply -- ? from 10.6 percent to 14.3 percent -- ? in the junior high school group.

"Now every one in five school children in Taipei has asthma," said Ou Liang-hsiu (歐良修), the pediatrician who analyzed the survey data.

The researchers also found out that fatter children are more likely to have asthma symptoms.

"Whenever a child puts on a kilogram of weight, he becomes 0.8 percent more likely to develop asthma," said Tsai Dian-lung (蔡典龍), a professor of statistics at National Taipei University, who helped quantify the overweight risk in asthma.

"Whenever one's BMI [body mass index] increases by one unit, he or she becomes 2.8 percent more likely to have asthma," Tsai added.

A person's BMI is calculated by dividing weight in kilograms by height in meters squared. A BMI of more than 30 is considered obese.

Doctors explained that increased weight might lead to poor lung functioning, which could be the key factor in inducing asthma.

The way weight affects the lungs could also affect the airways, especially during exercise.

"When people with asthma exercise, the mechanical impact of the weight on the lungs could also compromise the airways," said Huang Jing-long (黃璟隆), head of the department of pediatrics at Chang Gung Children's Hospital.

"When the breathing speeds up, the respiratory tract doesn't have enough time to moisturize the air and thereby becomes constricted. Then you have asthma symptoms like wheezing and coughing," he added.

Many school children and teenagers, however, get trapped in the vicious circle of gaining weight and developing asthma.

"We haven't quite understood the link between obesity and asthma. It is hard to determine which factor is the earlier cause," Huang said.

When children with asthma are taught to refrain from physical education classes in school or to spend less time in doing sports with their friends, Huang said, diminished exercise gradually leads to weight gain.

"Appropriate strategies for the reduction of body weight in children may contribute significantly to a reduced incidence of childhood asthma," Haung said.

Other asthma risk factors include children's exposure to air pollution and the parents' educational level, the study indicated.

"For instance, children who live in homes where trucks often pass by are 30 to 50 percent more likely to have asthma," Ou said, "Children living in homes where parents smoke are also more vulnerable to asthma."

Mothers with a higher degree of education also report more cases of child asthma to doctors, the study showed.

"We speculated that a mother with more education has a higher awareness of asthma, and therefore is more likely to seek medical help from doctors," Ou said.
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