Season of birth and lung fibrosis among workers exposed to asbestos

Our plain-English summary of Season of birth and lung fibrosis among workers exposed to asbestos, by T. Hannu, M.S. Jaakkola, L. Kivisaari, et al (Chronobiology International, 2007).

The study

• Authors: T. Hannu, M.S. Jaakkola, L. Kivisaari, M.S. Huuskonen, T. Vehmas
• Journal: Chronobiology International
• Published: 2007;24(3):539-51
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The season of birth has been suggested to influence the development of some diseases, but its role in lung fibrosis seems to not have been studied previously. The aim of this study was to investigate the relation between the season of birth and fibrotic abnormalities as detected radiologically in high-resolution computed tomography (HRCT) among workers exposed to asbestos. The HRCT examination was performed on 528 study subjects. Multiple ordinal regression analysis adjusting for covariates was used to study the relations between birth month or season and radiological fibrosis signs. Subjects born in autumn or winter had more extensive fibrotic changes than those born in spring or summer. This applied to all fibrotic changes, apart from subpleural nodules, but only the overall fibrosis score, septal lines, and honeycombing showed statistically significantly higher values in comparison to spring births. The highest scores were detected among those born in autumn and winter months (September-February). These results suggest that there are differences in fibrotic radiological abnormalities according to the season of birth in adults exposed to asbestos. Several hypotheses could explain the observed findings, including the effects of early respiratory infections, cold temperature, and differences in air pollution levels, as well as some metabolic and hormonal effects.

In plain English

This Finnish study asked whether the time of year a person was born was linked to signs of lung scarring (fibrosis) on high-resolution CT scans in workers exposed to asbestos. It included 528 workers from a national screening study of construction workers living in or near Helsinki. Of these, 106 had been diagnosed with asbestosis and 422 had pleural plaques on both sides and had smoked for more than 10 years. Three radiologists scored the scans without knowing the workers' histories. The analysis adjusted for age, sex, body size, smoking, occupation and years of asbestos exposure. Compared with workers born in spring, those born in autumn or winter had statistically significantly higher overall fibrosis scores. Autumn births also had higher septal line scores. Honeycombing scores were higher for winter births and for summer births. Several other signs showed no statistically significant difference from spring. The authors concluded that season of birth was significantly related to fibrosis on CT, with the highest scores in those born from September to February, and said further studies are needed to confirm this.

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 analysis of CT scans within a screening cohort of asbestos-exposed workers, using multiple ordinal regression to compare birth seasons
• Who was studied: 528 asbestos-exposed workers (518 men, 10 women; mean age 63, range 38 to 80) living in or near Helsinki, Finland, drawn from 602 construction workers in the Finnish ASBE-study. The group was 106 workers with asbestosis and 422 with bilateral pleural plaques and a smoking history of more than 10 years. Birth seasons: winter 126, spring 125, summer 146, autumn 131. Study dates were not given.
• Exposure: Occupational asbestos exposure (fiber types not specified) among construction workers. Occupations were insulators, plumbers, carpenters, electricians, engineers and other, used as a proxy for exposure intensity. Mean exposure duration was 26 years (range 2 to 48). The factor studied was season or month of birth.
• Main results:
  • Overall fibrosis score was significantly higher than in spring births for autumn births (regression coefficient 0.672, 95% CI 0.237 to 1.108, p = 0.002) and winter births (0.443, 95% CI 0.003 to 0.882, p = 0.048). Summer births did not differ significantly from spring births.
  • Septal lines were significantly higher in autumn births than in spring births (coefficient 0.582, 95% CI 0.145 to 1.020, p = 0.009). Winter and summer births did not differ significantly from spring births.
  • Honeycombing was significantly higher than in spring births for summer births (coefficient 1.246, 95% CI 0.109 to 2.383, p = 0.032) and winter births (1.174, 95% CI 0.038 to 2.310, p = 0.043). Autumn births did not reach significance (p = 0.062).
  • Subpleural nodules, curvilinear lines and visceral pleural fibrosis showed no statistically significant differences between any birth season and spring.
  • By month of birth, the overall fibrosis score peaked in January, with a three-month peak for September to November births. Septal lines peaked in October, also with a September to November peak. Honeycombing peaked in February, with a December to February peak.
• The authors' conclusion: The authors concluded that there is a significant relation between season of birth and pulmonary fibrosis detected by HRCT among asbestos-exposed workers, with the highest fibrosis signs in those born from September to February. They called for further studies in other populations. They suggested possible explanations, including viral respiratory infections, cold temperature, air pollution, and metabolic and hormonal effects, and called some of these pathways speculative.
• Limitations the authors state:
  • No detailed data on early childhood factors, such as childhood respiratory infections, were collected, so the hypothesized mechanisms could not be examined.
  • Because all subjects were asbestos-exposed, the study could not examine whether other types of fibrosis show a similar association.

Topics

Medical terms in this study, explained in our Lexicon: Fibrosis, High-Resolution CT (HRCT), Honeycombing.

Related studies

• Lung and pleural CT signs predict deaths: 10-year follow-up after lung cancer screening of asbestos-exposed workers — T. Vehmas, P. Oksa, et al. (2012)
• Cigarette smoking, asbestos, and pulmonary fibrosis — W. Weiss (1971)
• 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)
• Parenchymal and pleural fibrosis in construction workers — P. Oksa, H. Koskinen, et al. (1992)
• Asbestosis: interstitial pulmonary fibrosis and pleural fibrosis in a cohort of asbestos insulation workers: influence of cigarette smoking — R. Lilis, I.J. Selikoff, et al. (1986)
• Lung fibrosis in plutonium workers — L.S. Newman, M.M. Mroz, et al. (2005)

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