Longitudinal pattern of reported respiratory symptoms and accelerated ventilatory loss in asbestos-exposed workers

Our plain-English summary of Longitudinal pattern of reported respiratory symptoms and accelerated ventilatory loss in asbestos-exposed workers, by C.A. Brodkin, S. Barnhart, H. Checkoway, et al (Chest, 1996).

The study

• Authors: C.A. Brodkin, S. Barnhart, H. Checkoway, J. Balmes, G.S. Omenn, L. Rosenstock
• Journal: Chest
• Published: 1996;109(1):120-6
• Type of article: Randomized trial
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Studies investigating the relation between respiratory symptoms and change in ventilatory function have been limited by use of reported symptoms at a single point in time. To assess the relation between the longitudinal pattern of reported cough, phlegm, wheeze, and dyspnea and ventilatory loss, we prospectively investigated changes in FVC and FEV1 associated with development, resolution, or persistence of these symptoms over a 3- to 5-year period in 446 asbestos-exposed workers. Longitudinally reported symptoms changed frequently, with 52 to 61% of subjects reporting a specific symptom noting resolution or development of that symptom during follow-up. Initially reported symptoms were not predictive of accelerated loss of FVC or FEV1. In contrast, development of any new respiratory symptom, and to a lesser extent persistence of symptoms during follow-up, were associated with significantly greater ventilatory losses compared with asymptomatic individuals, ranging from 28 mL/yr in FEV1 for newly developed dyspnea, to 67 mL/yr in FVC for developed wheeze (p < 0.01). We conclude that development or persistence of respiratory symptoms over time, rather than the presence of symptoms per se, is predictive of future ventilatory loss. Recognition of interval changes in symptom reporting during surveillance of asbestos-exposed workers may effectively identify groups at risk for progressive ventilatory impairment.

In plain English

This study followed 446 men in the Seattle Asbestos Lung Cancer Chemoprevention Trial. Each had asbestos-related chest X-ray findings or at least 5 years in a trade with documented asbestos exposure. Over 3 to 5 years, the men answered a standard questionnaire on cough, phlegm, wheeze and breathlessness and had breathing tests (FVC and FEV1). Symptoms changed often: 52% (breathlessness) to 61% (wheeze) of men reporting a symptom either lost it or newly developed it. Symptoms reported at the start were not linked to significant changes in FVC or FEV1. The authors adjusted for smoking, age, baseline lung function and asbestos-related factors. After that, newly developed symptoms were linked to faster yearly loss than in men who never reported them: 32 to 67 mL per year for FVC and 28 to 39 mL per year for FEV1. Persistent symptoms were linked to smaller extra losses. Men whose symptoms resolved generally declined like symptom-free men. The authors concluded that developing or persistent symptoms, rather than symptoms at a single time, predicted future loss. They noted that high variability limits identifying individuals at risk.

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: Prospective longitudinal study of a subset of participants in a lung cancer chemoprevention trial, comparing symptom patterns at baseline and most recent follow-up with change in lung function
• Who was studied: 446 men in the Seattle Asbestos Lung Cancer Chemoprevention Trial (part of CARET) with at least 3 years of follow-up. They were a subset of 816 men randomized between 1985 and 1988, aged 45 to 74 at randomization. Mean follow-up was 3.7 years (range 2.9 to 5.2).
• Exposure: Asbestos exposure, with at least 15 years since first exposure. Entry required either chest X-ray evidence of asbestos-related effects or at least 5 years of employment in a trade with documented asbestos exposure. Fiber types are not specified.
• Main results:
  • Among men reporting a given symptom, 52% (dyspnea) to 61% (wheeze) reported either resolution or development of that symptom at follow-up compared with baseline.
  • Symptoms reported at baseline were not associated with significant changes in FVC, FEV1 or bronchodilator response. Baseline cough and wheeze were associated with statistically significantly greater annual losses in FEV1/FVC ratio of 0.4% and 0.5%, respectively.
  • In the adjusted analysis, newly developed symptoms were associated with accelerated decline in FVC compared with persistently asymptomatic men. The excess ranged from 32 mL/yr (cough) to 67 mL/yr (wheeze).
  • In the adjusted analysis, newly developed symptoms were associated with accelerated loss in FEV1 ranging from 28 mL/yr (dyspnea) to 39 mL/yr (cough).
  • Persistent symptoms were associated with accelerated loss to a lesser degree than new symptoms. This was most marked for wheeze and dyspnea (29 mL/yr and 26 mL/yr declines in FVC) and for cough (22 mL/yr decline in FEV1 and 0.6% decline in FEV1/FVC ratio), compared with men persistently not reporting those symptoms.
  • Men whose symptoms resolved during follow-up generally had the same annual decline in lung function as persistently asymptomatic men.
• The authors' conclusion: The authors concluded that development or persistence of respiratory symptoms over time, rather than the presence of symptoms per se, is predictive of future ventilatory loss. They also concluded that recognizing interval changes in symptom reporting during surveillance of asbestos-exposed workers may identify groups at risk for progressive ventilatory impairment.
• Limitations the authors state:
  • Possible selection bias: the subcohort with at least 3 years of follow-up was 55% of the randomized cohort, although the authors found no significant baseline differences between included and excluded participants.
  • Possible misclassification of smoking status. The study could not assess the effect of changes in smoking during follow-up.
  • Possible misclassification of chronic symptoms because of short-term acute symptoms, such as upper respiratory infections or irritant exposures.
  • The long interval between asbestos exposure and randomization meant lung function and symptom changes in early periods after exposure could not be assessed.
  • High variability in lung function loss, in both symptomatic and asymptomatic individuals, limits the usefulness of reported symptoms for identifying specific individuals at risk.

Topics

Medical terms in this study, explained in our Lexicon: Dyspnea, FEV1.

Related studies

• Correlation between respiratory symptoms and pulmonary function in asbestos-exposed workers — C.A. Brodkin, S. Barnhart, et al. (1993)
• Relation of occupational exposure to respiratory symptoms and asthma in a general population sample: self-reported versus interview-based exposure data — P.S. Bakke, R. Hanoa, et al. (2001)
• Longitudinal analysis of respiratory symptoms in population studies with a focus on dyspnea in marine transportation workers — V.H. Arrandale, M. Koehoorn, et al. (2009)
• The protective effect of beta-carotene and retinol on ventilatory function in an asbestos-exposed cohort — P. Chuwers, S. Barnhart, et al. (1997)
• Respiratory health in chrysotile asbestos miners in British Columbia: a longitudinal study — D.A. Enarson, V. Embree, et al. (1988)
• Lung function and respiratory symptoms in subjects with asbestos-related disorders: a cross-sectional study — B. Hilt, J.T. Lien, et al. (1987)

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