The effects of secondhand smoke exposure on HRCT findings among asbestos-exposed workers

Our plain-English summary of The effects of secondhand smoke exposure on HRCT findings among asbestos-exposed workers, by T. Vierikko, R. Järvenpää, J. Uitti, et al (Respiratory Medicine, 2008).

The study

• Authors: T. Vierikko, R. Järvenpää, J. Uitti, P. Virtema, P. Oksa, M.S. Jaakkola, T. Autti, T. Vehmas
• Journal: Respiratory Medicine
• Published: 2008;102(5):658-64
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: There is evidence suggesting that secondhand smoke (SHS) exposure is causally linked to adverse respiratory effects. We examined the relations between the exposure to SHS and radiological signs in chest high-resolution computed tomography (HRCT).

Methods: Asbestos-exposed workers (n=633) were imaged with HRCT, primarily to investigate potential occupational lung disease. After excluding current smokers, the study population included 361 ex- and 141 never-smokers. They answered a questionnaire on occupational exposures, smoking habits and SHS exposure. HRCT images were assessed for emphysema, ground-glass, irregular/linear and rounded opacities, honeycombing and several other signs. Regression analyses were adjusted for asbestos exposure, ex-smoking, age, body mass index and potential reader effect.

Results: Due to missing data the multivariate analyses were restricted to 310 participants aged 47.5-87.0 years. Their lifetime SHS exposure ranged between 0 and 193.5 pack-years (mean 23.5), and exposure in the past 12 months 0-30 packs (0.43). Total (B=0.005, 95% confidence intervals (95% CI) 0.002-0.008, p=0.000) and workplace (B=0.006, 95% CI 0.003-0.009, p=0.001) cumulative SHS exposures were significantly related to ground-glass opacities. Total SHS exposure in the last 12 months (B=0.027, 95% CI 0.000-0.054, p=0.048) and workplace exposure (B=0.027, 95% CI 0.000-0.054, p=0.048) were also significantly related to ground-glass opacities. Positive effects of SHS were also detected on irregular/linear opacities.

Conclusions: SHS exposure in the last 12 months and over lifetime significantly increases ground-glass opacity in HRCT, suggesting an early or subclinical desquamative interstitial pneumonia/respiratory bronchiolitis. This study further supports that SHS has adverse effects on the lungs that can be detected by X-ray methods.

In plain English

This cross-sectional study of asbestos-exposed workers in three Finnish cities examined whether secondhand smoke was linked to findings on high-resolution chest CT. After excluding current smokers, 310 men aged 47.5 to 87.0 (91 never-smokers, 219 ex-smokers) answered all questions on secondhand smoke at home and at work. Analyses were adjusted for asbestos exposure, past smoking, age, body mass index and scan reader. Ground-glass opacity scores rose by 0.005 per pack-year of lifetime exposure (95% CI 0.002 to 0.008) and by 0.027 per pack of exposure in the past 12 months (95% CI 0.000 to 0.054). Workplace exposure showed similar links. Home exposure was not significantly linked to ground-glass opacity in the main models. However, a table showed a significant link for lifetime home exposure after also adjusting for recent exposure. Lifetime exposure had a borderline link with irregular or linear opacities. Never-smokers analysed alone showed no significant associations. The authors concluded that secondhand smoke can induce lung changes visible on CT, possibly early respiratory bronchiolitis or desquamative interstitial pneumonia, but called for larger studies. The authors noted that only 310 of 502 non-smokers completed the questions.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: cross-sectional multicentre study
• Who was studied: 633 asbestos-exposed workers in Helsinki, Tampere and Turku, Finland, were scanned with HRCT and questioned in 2003–2004. After current smokers were excluded, 502 non-smokers remained (141 never-smokers and 361 ex-smokers). Of these, 310 men aged 47.5–87.0 years (mean 65) completed all secondhand smoke questions: 91 never-smokers and 219 ex-smokers.
• Exposure: Self-reported secondhand smoke exposure at home and at work, covering both the past 12 months (in packs) and a lifetime (in pack-years). Lifetime exposure ranged from 0 to 193.5 pack-years (mean 23.5). Past-12-month exposure ranged from 0 to 30 packs (mean 0.43). All participants were asbestos-exposed workers. Fiber types are not specified; asbestos exposure was entered as an index for adjustment.
• Main results:
  • Among the 310 participants, total lifetime secondhand smoke exposure was significantly related to increasing ground-glass opacity score. The score rose by B = 0.005 per pack-year (95% CI 0.002–0.008, p = 0.000).
  • Total secondhand smoke exposure in the past 12 months, measured in packs, was significantly related to increasing ground-glass opacity score (B = 0.027 per pack, 95% CI 0.000–0.054, p = 0.048).
  • Workplace exposure was related to ground-glass opacities in the past 12 months (B = 0.027 per pack, 95% CI 0.000–0.054, p = 0.048). It was also related over a lifetime (B = 0.006 per pack-year, 95% CI 0.003–0.009, p = 0.001). After adjustment for the other type of secondhand smoke exposure, the effects of recent exposure were no longer statistically significant.
  • In the main models, home secondhand smoke exposure (past 12 months and lifetime) was related to increased ground-glass opacities, but these effects did not reach statistical significance. For lifetime home exposure, the main-model result was B = 0.005, 95% CI 0.000–0.010, p = 0.059.
  • Table 3 used an additional model that was also adjusted for secondhand smoke exposure in the past 12 months. In that model, lifetime home exposure was significantly associated with ground-glass opacity (B = 0.005 per pack-year, 95% CI 0.002–0.007, p = 0.000).
  • Lifetime secondhand smoke exposure had a borderline significant effect on irregular and/or linear opacities (B = 0.006 per pack-year, 95% CI 0.000–0.013, p = 0.059).
  • Home secondhand smoke exposure in the past 12 months, measured in packs, was related to increased irregular and/or linear opacities (B = 1.873, 95% CI 0.512–3.233, p = 0.007). It was also related to honeycombing (B = 1.100, 95% CI 0.675–1.524, p = 0.000).
  • Relations between total secondhand smoke exposure and the other HRCT signs were not statistically significant.
  • When never-smokers were analysed alone, no significant associations were found. The authors attributed this probably to the small sample size.
  • In the multivariate analyses, ex-smoking was related to emphysema only, and asbestos exposure was related to irregular/linear opacities only.
• The authors' conclusion: The authors concluded that secondhand smoke exposure can induce processes in the lungs seen as ground-glass opacity and linear/irregular opacities on HRCT. They suggested these may be early signs of respiratory bronchiolitis or desquamative interstitial pneumonia. They added that these effects should be investigated in larger samples with heavier exposure levels before making any definite conclusions.
• Limitations the authors state:
  • The number of never-smokers was small.
  • Only 310 of 502 participants (61.8%) completed all the secondhand smoke questions.
  • Exposure was self-reported, which may have caused some misclassification.
  • Most participants were construction workers working mainly outdoors, which may have diluted their workplace exposure. Together with the limited sample size, this may have affected the ability to detect associations with emphysema or other signs.
  • Participants were not a random population sample, so the results cannot be extrapolated directly to the general population.
  • The scans may have over-detected or under-detected abnormalities.

Topics

Medical terms in this study, explained in our Lexicon: High-Resolution CT (HRCT), Occupational Lung Disease, Occupational Exposure, Habit, Emphysema, Honeycombing, Asbestos Exposure, confidence interval.

Related studies

• Scoring CT/HRCT findings among asbestos-exposed workers: effects of patient's age, body mass index and common laboratory test results — T. Vehmas, L. Kivisaari, et al. (2005)
• Early life exposure to environmental tobacco smoke alters immune response to asbestos via a shift in inflammatory phenotype resulting in increased disease development — T.A. Brown, A. Holian, et al. (2016)
• Clinical and HRCT screening of heavily asbestos-exposed workers — T. Vierikko, R. Järvenpää, et al. (2010)
• Pulmonary function, smoking habits, and high resolution computed tomography (HRCT) early abnormalities of lung and pleural fibrosis in shipyard workers exposed to asbestos — S. Neri, P. Boraschi, et al. (1996)
• Chest CT scan findings in World Trade Center workers — R.E. de la Hoz, J. Weber, et al. (2019)
• Chest HRCT signs predict deaths in long-term follow-up among asbestos exposed workers — T. Vehmas, P. Oksa (2014)

Browse more research in Respiratory Medicine, or return to medical research.