Young smoker CT scans show lung abnormalities, lung function loss over 3 years
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Key takeaways:
- Having a smoking history of more than 10 pack-years negatively impacts lung CT findings.
- Heightened COPD Assessment Test scores and lung function decline are significantly related.
SAN DIEGO — Lung abnormalities appeared more frequently on CT scans from young current smokers vs. never smokers, according to research presented at the American Thoracic Society International Conference.
Further, researchers found a significant relationship between an increase in these abnormalities and a faster annualized rate of FEV1 decline.
“A relatively short period, minimum 10 pack-years ... of regular tobacco smoking results in identifiable lung abnormalities before there’s any diagnosis of COPD,” Jadwiga A. Wedzicha, MD, FRCP, ATSF, professor of respiratory medicine at the National Heart and Lung Institute at Imperial College London and Royal Brompton Hospital, said during her presentation.
In the large, prospective British EArly COPD Network (BEACON) study, Wedzicha and colleagues assessed 431 current tobacco smokers (median age, 39 years; 60% men; 82.4% white) aged 30 to 45 years with more than a 10 pack-year smoking history (median, 16 pack-years) and normal spirometry (FEV1 > 80% predicted) against 67 age-matched never smokers (median age, 36 years; 52.2% men; 80.6% white) to compare the prevalence of lung abnormalities on quantitative thoracic CT scans and determine how these measurements impact lung function at a 3-year follow-up.
Of the total smoking cohort, 69.8% had a normal FEV1/FVC ratio without chronic bronchitis, 23% had a normal FEV1/FVC ratio with chronic bronchitis and the remaining 7.2% had an abnormal FEV1/FVC ratio.
Between the two sets of individuals, disease probability-defined air trapping was significantly more prevalent among current smokers vs. nonsmokers (7.4% vs. 4.7%; P < .001). The prevalence of disease probability-defined emphysema was similar in the group of smokers and the group of nonsmokers (0.05% vs. 0.03%).
In terms of ground glass opacities, more current smokers had this on their CT scans than nonsmokers (1.3% vs. 0.3%; P < .001).
Bronchovascular prominence was also found more among those who smoked vs. those who did not smoke (13.8% vs. 12%; P < .001), according to Wedzicha.
Researchers classified small vessels as less than 0.75 mm and found that smokers vs. nonsmokers had a higher small vessel volume to total pulmonary vessel volume ratio (0.32 vs. 0.3; P < .001).
Additionally, researchers observed that older age within the 30-to-45-year range raised the percentage of air trapping and emphysema. Another factor that significantly heightened air trapping was a higher number of pack-years, Wedzicha said during her presentation.
For the follow-up CT scan in the group of smokers (n = 368), the median time was 32 months, during which researchers observed a FEV1 reduction of 36.4 mL/year (95% CI, –44.4 to –28.4; P < .001).
At 3 years, baseline FEV1 per 1% increase in the studied CT measurement did not significantly differ in all but one CT parameters: small vessel volume/total pulmonary vessel volume (P = .036).
In contrast, the rate of FEV1 change per 1% increase in CT measure per year between baseline and 3 years was significant for air trapping (–1.5 mL/year), emphysema (–19.5 mL/year), small vessel volume/total pulmonary vessel volume (–1.1 mL/year), ground glass opacity (–3.4 mL/year) and bronchovascular prominence (–2.6 mL/year).
The COPD Assessment Test (CAT) was completed by smokers to capture changes in symptoms over time.
Between baseline and 3 years, a rise in CAT score by one unit corresponded to a 13.4 mL decrease (P = .003) in baseline FEV1 and significantly impacted the FEV1 yearly rate by –1.4 mL/year (P = .025).
A greater number of individuals in the smoking cohort had an FEV1 decline of less than 60 mL per year vs. 60 mL per year or more (n = 265 vs. n = 103), and Wedzicha highlighted that these two sets of individuals did not significantly differ from each other across various baseline characteristics and CT changes.
“We have identified abnormalities early in the natural history of disease, and this has really been a gap in our knowledge,” Wedzicha said.
“The radiological abnormalities relate to prior smoking, and we have shown already in these young smokers in the study a degree of subclinical small airways dysfunction,” she continued. “We generated CT data that relates to subsequent FEV1 decline.”
Wedzicha noted that a phase 2 study is planned to assess CT images of the BEACON cohort at a 5-year follow-up.