Wheezing Prevalence Patterns Established by Age 6
Among children who exhibit asthma-like symptoms during preschool, researchers have found that patterns of wheeze prevalence and levels of lung function are established by age 6 and do not significantly change for at least 10 years. Their findings were reported in the second issue of the November 2005 American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.
Fernando D. Martinez, M.D., of the Arizona Respiratory Center at the University of Arizona Health Sciences Center in Tucson, along with eight associates, studied 826 children based on the occurrence of "wheezing lower respiratory illnesses" before age 3 and active wheeze at age 6. Among this group, there were 425 "never wheezers," 164 "transient early wheezers," 113 "persistent wheezers" and 124 "late-onset wheezers."
The four types of pre-school wheeze that were used to classify the children were defined as based on either the presence or absence of at "least one physician-diagnosed wheezing 'lower respiratory illness' in the first 3 years of life," and at least "one episode of 'parent-reported wheeze' during the past year for the child at age 6."
During the follow-up on each child at ages 8, 11, 13 and 16 years, parents completed a questionnaire on the youngster's prevalence of wheeze (with or without a cold). Researchers characterized current wheeze at each age as either "no wheeze," "infrequent wheeze" (one to three episodes in the past year) or "frequent wheeze" (four or more episodes in the past year). The investigators also performed a pulmonary function test on each participant at age 11.
"There was no significant change in lung function among subjects within either of the three different wheezing groups or the non-wheezing group studied, relative to their peers, from age 6 to 16 years," said Dr. Martinez.
According to the authors, more than 75 percent of the "never" and "transient early wheezers" reported no wheezing between ages 8 and 16. Among the small proportion of children in those groups who reported wheezing, the researchers said that most had only infrequent episodes.
"As we published in an earlier paper, transient early wheezers start life with levels of lung function that are significantly lower than those of children who had no wheezing episodes during the first 6 years of life," said Dr. Martinez. "We now confirm that these children continue to have lower levels of lung function at ages 11 and 16 years, and that, relative to their peers, their levels of lung function remain stable during their school years."
Based on prior published research, however, the authors believe that compromised lung function during the children's school years could have a strong association with the likelihood of having bronchial hyperresponsiveness, decreased lower lung function and persistent asthma symptoms by age 42.
The researchers note that the children included in this analysis were enrolled at birth in the Tucson Children's Respiratory Study, starting in 1988.