Lung Function of Adults Born at Very Low Birth Weight

To assess the lung function in adults who were very low birth weight (VLBW) infants in comparison with controls and to assess if bronchopulmonary dysplasia (BPD) added further insult to their underlying pulmonary function.

The study population consisted of 226 adults, aged 26 to 30 years, selected from the 1986 New Zealand VLBW cohort (birth weight <1500 g). One hundred adults born at term in 1986 who did not require NICU admission served as age-matched controls.

In this retrospective cohort analysis, participants underwent anthropometric, health, and welfare assessments. Participants then completed pulmonary function testing, including spirometry, plethysmographic lung volumes, single-breath diffusing capacity of the lung for carbon monoxide (D_LCO), and single-breath nitrogen washout (SBN₂). Respiratory physiologists were blinded as to the participants’ group.

63% of VLBW adults had normal spirometry versus 82% of controls (P = .0004), with the predominant pattern of abnormality being obstruction (35% in VLBW adults versus 14% in controls). VLBW adults had lower z scores for FEV₁, FEV₁/FVC, and FEF _25-75, all of which demonstrated statistical significance. VLBW adults also had significantly lower z scores for both D_LCO (P < .0001) and transfer coefficient for carbon monoxide (K_CO) (P < .0001), and a higher phase III slope of SBN₂ (P = .004). Differences between groups persisted when adjusting for multiple variables including sex and smoking status. Among VLBW adults, those diagnosed with BPD had significantly lower z scores for FEV₁, FEV₁/FVC, and FEF _25-75, and a higher phase III slope of SBN₂ compared with those without BPD. No statistically significant difference was found among VLBW adults with or without BPD in D_LCO or K_CO.

VLBW adults had a higher incidence of airway obstruction, reduced gas exchange, and ventilatory inhomogeneity compared with controls. VLBW adults with BPD had further reduction in measures of airway obstruction and ventilatory inhomogeneity.

This study provides further evidence that infants with VLBW have abnormalities in lung function that persist into adulthood. It adds to the literature by including measurements of gas exchange (D_LCO and K_CO) and ventilatory inhomogeneity (SBN₂), which can be worsened by modifiable behaviors such as smoking. Given their baseline abnormalities in lung function, VLBW patients who develop recurrent respiratory infections should also be evaluated for the development of bronchiectasis. Clinicians should remain cognizant of the long-term multidisciplinary follow-up and counseling needed for infants with VLBW.