Effect of lifetime cigarette consumption on time domain spirogram indices

Our plain-English summary of Effect of lifetime cigarette consumption on time domain spirogram indices, by T. Nakadate, T. Sato, J. Kagawa, et al (Industrial Health, 1994).

The study

• Authors: T. Nakadate, T. Sato, J. Kagawa, T. Yagami
• Journal: Industrial Health
• Published: 1994;32(1):29-40
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A cross-sectional analysis on the dose-related change in time domain spirogram indices induced by lifetime cigarette consumption was conducted to examine the ability of those indices to detect early changes in the lung periphery in comparison with conventional spirometric indices. The subjects were asymptomatic healthy male workers from three occupational cohorts including asbestos workers and welders. They were asked to perform the forced expiration maneuver at least three times to obtain reliable results. A total of 893 subjects were enrolled in the study, and 484 of them who were aged 30 years or more and were free from chronic respiratory symptoms and abnormalities in chest radiography and spirometry, were analyzed. Although conventional indices, such as forced expiratory volume in one second and maximal midexpiratory flow, were not significantly different between smokers and nonsmokers, the standard deviation of transit times and of time constant distribution in smokers were significantly elevated compared with nonsmokers. Furthermore a dose-related change according to lifetime cigarette consumption was observed in those indices. We conclude that time domain spirogram indices, especially the standard deviation of time constant distribution, would be more useful than conventional indices in detecting early changes in the lung periphery.

In plain English

This cross-sectional study from Japan examined how lifetime cigarette smoking related to "time domain" measures from a forced-breathing test (spirogram) in healthy men, compared with conventional measures such as FEV1. Subjects came from three worker groups the authors followed from 1984 and 1985: employees of two asbestos-using factories and welders at a machine factory. Of 893 men enrolled, 484 aged 30 or older without chronic respiratory symptoms, chest X-ray abnormalities or abnormal spirometry were analyzed. By current job, 123 were exposed to asbestos dust, 213 to welding fumes and gases, and 148 had no noticeable exposure to either. Conventional measures did not differ significantly between smokers and never-smokers, but the standard deviation of transit times and Sigma (the spread of time constants) were significantly higher in smokers. Only Sigma showed a statistically significant dose-related change, being higher in the 10-19 and 20-29 pack-year groups than in never-smokers. Time domain measures did not differ significantly by occupational group. The authors concluded these parameters would be useful for detecting early smoking-related change. They noted there were few heavy smokers and called for confirmation in other settings.

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 the first acceptable lung function test from workers in three longitudinally followed occupational cohorts.
• Who was studied: Male workers in Japan: employees of two asbestos-using factories of one company and welders at a machine-producing factory. First surveys were in autumn 1984 (welders) and spring 1985 (asbestos factories), with follow-up up to 1989. 893 were enrolled. After excluding men with respiratory illness or chest X-ray abnormalities (34), low spirometry (40), chronic respiratory symptoms (123), or unreliable smoking answers (25), 572 remained, and the 484 aged 30 or more were analyzed.
• Exposure: The main exposure was lifetime cigarette consumption in pack-years. Occupational status was a secondary factor, assigned by job at the time of examination: 123 exposed to asbestos dust, 213 to welding fumes and gases, and 148 without noticeable exposure. Monitoring showed concentrations below Japanese permissible levels, which the article gives as 2 fibers/cc for chrysotile asbestos, 1 mg/m3 for respirable dust and 0.1 ppm for ozone.
• Main results:
  • About 20% of the analyzed subjects were never-smokers, and smokers had a mean of about 18 pack-years. The proportion who had ever smoked did not differ significantly across the three occupational groups (chi-square 4.4, p = 0.11).
  • Comparing all smokers with never-smokers, adjusted for age, occupational status and squared height where needed, there was no significant difference in FEV1, FEV1%, FEF25, MMF, loge(MTT) or Mu. Loge(STT) (standard deviation of transit times) and Sigma were significantly higher in smokers.
  • With smokers split into four pack-year categories, a dose-related change was seen in almost all indices but was statistically significant only for Sigma. The 10-19 and 20-29 pack-year categories had significantly larger Sigma values than never-smokers.
  • Mu showed a moderate increase only in the highest consumption category (30 pack-years or more). The authors state this increase was not statistically significant.
  • By occupational group, welders had significantly larger FEV1 and FEF25. There was no statistically significant difference in loge(MTT), loge(STT), Mu or Sigma among the asbestos-exposed, welding-exposed and unexposed groups.
• The authors' conclusion: The authors concluded that time constant parameters calculated from a forced spirogram would be useful in detecting early obstructive change caused by smoking in peripheral lung units, at a stage when conventional spirometric indices have not yet shown significant change.
• Limitations the authors state:
  • Because the subjects were relatively young, there were too few heavy smokers for further analysis of Mu and smoking.
  • Occupational exposure might have influenced the results. The authors judged significant bias unlikely because exposure levels were below permissible limits, smoking rates were similar across groups, and occupation was adjusted for.
  • The lack of difference in conventional indices might partly reflect the eligibility criteria, since only men with normal spirometry were analyzed.
  • The finding needs confirmation in other study settings, and changes in these indices over time with smoking still need to be examined.

Topics

Medical terms in this study, explained in our Lexicon: Spirogram, Spirometry.

Related studies

• Effects of cigarette smoke dose and time after smoke exposure on uptake of asbestos fibers by rat tracheal epithelial cells — A. Churg, J. Hobson, et al. (1990)
• Effects of cigarette smoke on the clearance of short asbestos fibres from the lung and a comparison with the clearance of long asbestos fibres — A. Churg, J.L. Wright, et al. (1992)
• UK Naval Dockyards asbestosis study: survey of the sample population aged 50-59 years — C.E. Rossiter, P.G. Harries (1979)
• Railroad workers with pleural plaques: I. Spirometric and nitrogen washout investigation on smoking and nonsmoking asbestos-exposed workers — U. Hjortsberg, P. Orbaek, et al. (1988)
• Relation between lung asbestos fibre burden and exposure indices based on job history — K. Takahashi, B.W. Case, et al. (1994)
• Absence of synergism between exposure to asbestos and cigarette smoking in asbestosis — J.M. Samet, G.R. Epler, et al. (1979)

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