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Background: Pulmonary nodules (PNs) are clinically challenging because differentiation between benign and malignant PNs is not possible at CT detection; recurring CT examinations and invasive procedures are often required in PN follow-up.

Purpose: To investigate PN prevalence in a middle-aged population and the risk factors associated with these nodules.

Materials and Methods: In this secondary analysis of the cross-sectional population-based Swedish CArdioPulmonary bioImage Study (known as SCAPIS, from November 2013 to November 2018), participants aged 50-64 years with chest CT data were analyzed. Risk factors such as smoking history, occupational exposure (vapor, dust, gas, and fumes), and lung diseases were derived from comprehensive questionnaires. Robust Poisson regression was used to evaluate associations, adjusted for age and sex, between potential risk factors and the binary outcome of nodule presence or absence. Prevalence ratios (PRs), adjusted for age and sex, and 95% CIs were estimated.

Results: Among 29 574 participants (median age, 57.4 years; IQR, 53.7-61.2 years; 15 168 women), solid nodules sized 100-300 mm3, part-solid, and ground-glass nodules were found in 1420 (4.8%), 199 (0.7%), and 430 (1.5%), respectively. The prevalence of solid nodules among participants who never, formerly, and currently smoked was 32.5% (4713 of 14 515), 34.5% (3602 of 10 437), and 37.9% (1381 of 3644), respectively. Solid nodules sized 100-300 mm3 were associated with current smoking (PR, 1.38; 95% CI: 1.19, 1.60), chronic obstructive pulmonary disease (PR, 1.72; 95% CI: 1.17, 2.53), occupational exposure (PR, 1.31; 95% CI: 1.11, 1.54), emphysema (PR, 1.56; 95% CI: 1.31, 1.86), reticulation (PR, 1.96; 95% CI: 1.47, 2.61), and bronchiectasis (PR, 2.03; 95% CI: 1.64, 2.50). In participants who had never smoked, associations were found between solid nodules at least 100 mm3 and reticulation (PR, 2.28; 95% CI: 1.55, 3.36), reported lung disease other than asthma or chronic obstructive pulmonary disease (PR, 2.26; 95% CI: 1.49, 3.43), and bronchiectasis (PR, 2.17; 95% CI: 1.60, 2.94).

Conclusion: PN prevalence was approximately the same in a middle-aged population regardless of smoking history. In participants who had never smoked, nodules were linked to reported lung disease, reticulation, and bronchiectasis.