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Age and Small Airway Imaging Abnormalities in Subjects With and Without Airflow Obstruction in SPIROMICS

ARTICLE: Age and Small Airway Imaging Abnormalities in Subjects With and Without Airflow Obstruction in SPIROMICS

AUTHORS: Carlos H. Martinez, Alejandro A Diaz, Catherine Meldrum, Jeffrey L. Curtis, Christopher B. Cooper, Cheryl Pirozzi, Richard E. Kanner, Robert Paine, III, Prescott G Woodruff, Eugene R Bleecker, Nadia N Hansel, R. Graham Barr, Nathaniel Marchetti, Gerard J Criner, Ella A Kazerooni, Eric A. Hoffman, Brian D Ross, Craig J Galban, Christine T Cigolle, Fernando J Martinez, MeiLan K Han and for the SPIROMICS Investigators

JOURNAL: Am J Respir Crit Care Med. 2016 Aug 26. [Epub ahead of print]


RATIONALE: Aging is associated with reduced forced expiratory volume in the first second (FEV1) to forced vital capacity (FVC) ratio (FEV1/FVC), hyperinflation and alveolar enlargement, but little is known about how age affects small airways. We hypothesized that chest computed tomography(CT)-assessed functional small airway would increase with age, even among asymptomatic individuals.

METHODS: We used parametric response mapping analysis of paired inspiratory/expiratory CTs to identify functional small airway abnormality (PRMFSA) and emphysema (PRMEMPH) in the SPIROMICS cohort. Using adjusted linear regression models, we analyzed associations between PRMFSA and age in subjects with or without airflow obstruction. We subdivided participants with normal spirometry based on respiratory-related impairment [six minute walk distance <350 m; mMRC ≥2; chronic bronchitis; SGRQ >25; respiratory events requiring treatment (antibiotics and/or steroids or hospitalization) in the year before enrollment].

RESULTS: Among 580 never- and ever-smokers without obstruction or respiratory impairment, PRMFSA increased 2.7% per decade, ranging from 3.6% (ages 40-50) to 12.7% (ages 70-80). PRMEMPH increased non-significantly [0.1% (ages 40-50) to 0.4% (ages 70-80)(p=0.34)]. Associations were similar among non-obstructed individuals with respiratory-related impairment. Increasing PRMFSA in subjects without airflow obstruction was associated with increased FVC (p=0.004) but unchanged FEV1 (p=0.94), yielding lower FEV1 /FVC ratios (p<0.001). Although emphysema was also significantly associated with lower FEV1 /FVC (p=0.04), its contribution relative to PRMFSA in those without airflow obstruction was limited by its low burden.

CONCLUSIONS: In never- and ever-smokers without airflow obstruction, aging is associated with increased FVC and CT-defined functional small airway abnormality regardless of respiratory symptoms.

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Kelsey Bennett