Reduced lung function in infancy is associated with wheezing at age 18, but only in smokers, researchers reported.
In an Australian birth cohort, persistent wheezing throughout life was associated with a marked reduction in lung capacity in the first month of infancy, according to Steve Turner, MD, of Royal Aberdeen Children's Hospital in Aberdeen, Scotland, and colleagues.
But wheezing that began in early adulthood was associated with reduced infant lung function only among those who also smoked, Turner and colleagues reported online in JAMA Pediatrics.
That finding was unexpected, Turner and colleagues reported, and suggests that preventing young children with asthma symptoms and reduced lung function from smoking "might prevent persisting symptoms of obstructive airways disease."
The study is the first to report an association between reduced lung function in infancy and wheezing beyond childhood, although other studies have shown that early wheezing persists into childhood.
The Perth Infant Asthma Cohort included 243 babies whose lung function was assessed at 4 weeks, with follow-ups at 6, 12, and 18 years. The follow-up at age 6 included 123 of the initial participants, at age 12 there were 194 of the original cohort, and at age 18, 150.
For this analysis, the 18-year-old participants were divided into groups based on wheezing: no wheezing at any age, wheezing at 18 and at least one earlier assessment (persistent wheeze), wheezing at earlier assessments but not at 18 (remittent wheeze), wheezing at 18 but not earlier (late-onset wheeze).
The 13 participants with persistent wheeze were significantly more likely to have had reduced lung function as infants, compared with the 96 who had never had wheezing. Specifically, they had a 43% reduction, on average, in maximal flow at functional residual capacity (or V'maxFRC).
Persistent wheeze was also independently associated with:
- Atopy during infancy (OR 7.1, 95% CI 1.5 to 34.5, P=0.01)
- Maternal asthma (OR 6.8, 95% CI 1.4 to 32.3, P=0.02)
- Active smoking at 18 (OR 4.8, 95% CI 1.0 to 21.3, P=0.04)
When the researchers divided the participants according to quartiles of infant V'maxFRC, they found that 78% of 18-year-old smokers with wheeze fell into the lowest category, compared with just 29% of the nonsmokers.
Conversely, among those who had been in the highest quartile as infants, 29% of the current smokers and 21% of the nonsmokers had wheeze, Turner and colleagues found.
Analysis showed that trends across the quartiles were significant (at P=0.007) for smokers, but not for nonsmokers.
The links between reduced lung function in infancy, smoking, and new wheezing might have important public health implications, the researchers commented.
But the numbers in the study were small, they cautioned, so that the result "ideally should be confirmed in other cohorts."
The findings suggest that poet Alexander Pope's view of education -- "just as the twig is bent, the tree's inclined" – apply also to lung function, commented Kai-Håkon Carlsen, MD, PhD, of Norway's Oslo University Hospital.
Previous research has tracked low lung function from infancy into adolescence and young adulthood, he noted in an accompanying editorial, but Turner and colleagues worked backward – showing that people in late adolescence with poor lung function were precisely those who had low lung function in infancy.
The study is additional evidence that early reductions in lung function have important effects on respiratory health later in life, Carlsen concluded.
Primary source: JAMA Pediatrics
Source reference: Mullane D, et al "Reduced infant lung function, active smoking, and wheeze in 18-year-old individuals" Arch Pediatr Adolesc Med 2013; 167(2): 1-6.
Additional source: JAMA Pediatrics
Source reference: Kai-H Carlsen "Neonatal lung function and later respiratory consequences" Arch Pediatr Adolesc Med 2013; 167(2): 1-2.