Birth weight influences lung function, airway responsiveness

Key takeaways:

• The group with low birth weight had reduced expiratory airflow at low lung volume at age 1 month.
• The group with high birth weight had increased airway responsiveness at age 12 months.

WASHINGTON — Birth weight influences lung function and airway responsiveness beyond changes in lung size, according to data presented at the American Thoracic Society International Conference.

“Meta-analysis demonstrates a strong inverse association between birth weight and restrictive lung impairment and a weaker association with airflow obstruction,” Kimberley Wang, PhD, senior research fellow, School of Human Sciences, The University of Western Australia, told Healio.

“In animals, growth restriction leads to airway wall abnormalities and changes in airway responsiveness,” she continued. “This study, therefore, aims to examine the relationship between birth weight, lung function and airway responsiveness in the Perth Infant Asthma Follow-up (PIAF) Birth Cohort.”

Kimberley Wang

The longitudinal PIAF Birth Cohort comprised 253 infants recruited between 1987 and 1989 from a general antenatal clinic in Perth. There was no preselection for family history of asthma or atopy.

Infants were born at term, defined as 37 weeks or more of gestational age. The researchers categorized low birth weight as less than 2.5 kg, normal birth weight as 2.5 to 4 kg and high birth weight as more than 4 kg.

The researchers also assessed V’maxFRC, which is a measure of expiratory airflow at low lung volume, at age 1, 6 and 12 months with adjustments for body length and airway responsiveness to histamine.

Infants with low birth weight had lower V’maxFRC than those with normal birth weight (P = .034) at 1 month. Infants with high birth weight had increased airway responsiveness compared with the normal birth weight group (P = .012) at 12 months.

At age 6, 11, 18 and 24 years, the researchers assessed airway responsiveness and lung function based on FEV₁ and forced vital capacity (FVC) z scores.

There were positive correlations between birth weight and FEV₁ (P = .017) and FVC (P = .02) at age 11 years. However, the researchers did not find any other relationship between birth weight, lung function and airway responsiveness at any other time point. A doctor diagnosis of asthma was independent of birth weight as well.

“Findings reveal a birth weight effect that extends beyond changes in lung size,” Wang said. “Therefore, airway dysfunction should be considered a precursor rather than a consequence of disease processes.”

Wang encouraged doctors “to follow up with the respiratory health of infants born with either low or high birth weight at least through childhood.”

Next, Wang said, the researchers will work “to understand why and what are the different underlying mechanisms in low vs. high birth weight that contribute to airway dysfunction.”

For more information:

Kimberley Wang, PhD, can be reached at kimberley.wang@uwa.edu.au.