A comprehensive study of nonsmokers found a high prevalence of lung nodules, with 42% of participants having at least one solid nodule measuring 30 mm³ or larger. The research, published in Radiology, also revealed that 11.1% of participants had clinically relevant nodules (≥100 mm³) requiring further evaluation, while 2.3% had actionable nodules (≥300 mm³).

The Imaging in Lifelines study, conducted in the northern Netherlands, analyzed low-dose chest computed tomography (CT) scans from 10,431 participants aged 45 years and older. The median age of the population was 60.4 years, and 56.6% were women. Of the participants, 46.1% were never smokers, and 53.9% were former smokers.

Key Findings

Overall nodule prevalence was higher in men (47.5%) than in women (37.7%). Prevalence increased with age, from 39.4% in men and 27.7% in women aged 45 to 49.9 years to 60.7% in men and 50.9% in women aged 80 years and older. Clinically relevant nodules were found in 14.0% of men and 8.9% of women. Actionable nodules were present in 2.4% of men and 2.1% of women.

The study utilized semiautomated volumetric quantification for nodule measurement, with a 30-mm³ threshold for nodule presence. Seven trained readers interpreted the CT scans, recording nodule presence, size, location, and morphological features.

Nodule size distribution was as follows:

• 30 to <100 mm³: 73.6% (3,222 of 4,377) of nodules
• 100 to < 300 mm³: 21.0% (918 of 4,377) of nodules
• ≥ 300 mm³: 5.4% (237 of 4,377) of nodules.

The number of nodules per individual varied:

• One nodule: 23.3% (2,430 of 10,431)
• Two nodules: 9.3% (975 of 10,431)
• Three nodules: 4.2% (433 of 10,431)
• Four nodules: 2.1% (224 of 10,431)
• Five or more nodules: 3.0% (315 of 10,431).

Nodule location and lobe distribution were reported as:

• Central: 18.8% (825 of 4,377)
• Peripheral: 81.2% (3,552 of 4,377)
• Right upper lobe: 21.9% (957 of 4,377)
• Right middle lobe: 12.7% (555 of 4,377)
• Right lower lobe: 25.3% (1,106 of 4,377)
• Left upper lobe: 15.2% (666 of 4,377)
• Left lower lobe: 25.0% (1,093 of 4,377).

Nodule characteristics were detailed:

• Shape: oval (28.3%), polygonal (21.1%), triangular (31.1%), spherical (9.7%), or irregular (9.9%)
• Margin: smooth (87.5%), fuzzy (4.0%), irregular (5.8%), lobulated (1.8%), or spiculated (0.9%)
• Attached structures: intraparenchymal (56.5%), peribronchial (8.3%), pleural attached (10.0%), or vascular attached (25.3%).

Former smoker characteristics were reported:

• Median pack-years: 7.9 (interquartile range [IQR] = 3.3-15.0)
• Median quitting years: 27.4 (IQR = 16.8-38.1)
• Men: median of 10.4 pack-years (IQR = 4.8-18.6)
• Women: median of 6.0 pack-years (IQR = 2.6-12.0).

Typical perifissural nodules (PFNs), which were considered benign, were found in 21.5% of participants with nodules. The overall prevalence of PFNs was 9.0% of all participants, with PFNs ≥10 mm found in 0.1% (10 of 10,431) of participants. The median volume of PFNs was 61.0 mm³ (68.0 mm³ for men, 55.0 mm³ for women).

The study used high-pitch 120-kVp low-dose chest CT with reconstruction parameters of 512 × 512 matrix, 350-mm field of view, and 1.0-mm section thickness.

Statistical analysis revealed significant correlations between age and nodule prevalence in both men (r = 0.148, P < .001) and women (r = 0.165, P < .001).

Notably, the 11.1% prevalence of clinically relevant nodules in this nonsmoking population was comparable to the 10.7% baseline prevalence reported in the NELSON study, a lung cancer screening trial of high-risk smokers.

Some limitations of the study included potential selection bias due to recruitment strategies, single-reading image interpretation, and a predominantly White study population (98.0% of participants), which may limit generalizability to other ethnicities.

The authors concluded that lung nodules were present in a substantial proportion of all age groups in this nonsmoking population, with a slightly higher prevalence in men than women. These findings may have implications for the management and follow-up of incidentally detected lung nodules in non–high-risk populations.

Disclosures of conflicts of interest can be found in the study.