Educational differences in lung cancer mortality in male smokers

Our plain-English summary of Educational differences in lung cancer mortality in male smokers, by P. Martikainen, E. Lahelma, S. Ripatti, et al (International Journal of Epidemiology, 2001).

The study

• Authors: P. Martikainen, E. Lahelma, S. Ripatti, D. Albanes, J. Virtamo
• Journal: International Journal of Epidemiology
• Published: 2001;30(2):264-7
• Type of article: Randomized trial
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: To assess the extent of lung cancer mortality differentials by education while adjusting for exposure to tobacco smoke and asbestos based on survey questions.

Methods: Alpha-Tocopherol, Beta Carotene Cancer Prevention (ATBC) Study of 50-69-year-old Finnish male smokers enrolled 1985-1988. These analyses are based on the placebo group and the alpha-tocopherol supplementation group, altogether 14 011 men, with full information on tobacco smoking. Mortality follow-up was to the end of April 1993 and it was based on the complete death certificate register of the Statistics Finland.

Results: Lung cancer mortality of basic-educated men was 32% (rate ratio [RR] = 1.32; 95% CI : 0.93-1.87) higher than that of better-educated men in the ATBC Study. The excess is practically unchanged when additional adjustment was made for age at initiation, duration of smoking, current smoking at baseline and at first follow-up, smoke inhalation, occupational exposure to asbestos and interactions between asbestos exposure and all smoking variables. This excess mortality was about 40% of the similar excess observed in the general population of men of similar age.

Conclusions: Educational differences in lung cancer mortality in the total Finnish population are likely to be mainly caused by differences in exposure, particularly to active smoking. Further understanding of the determinants and consequences of socioeconomic differences in smoking behaviour are of major scientific and public health importance.

In plain English

The authors analysed data from the Alpha-Tocopherol, Beta Carotene Cancer Prevention (ATBC) Study, a randomized trial of Finnish male smokers aged 50 to 69 recruited in 1985–1988. Using 14 011 men from the placebo and alpha-tocopherol-only groups, they compared lung cancer death rates by education. They adjusted for smoking history and for occupational asbestos exposure, which was asked about as ever working in asbestos mining, production or insulating jobs (about 2% of men). Over an average 5.5 years, 238 men died of lung cancer. Lung cancer mortality among basic-educated men was 32% higher than among better-educated men (rate ratio 1.32; 95% CI 0.93 to 1.87). Further adjustment for smoking, asbestos and their interactions left this practically unchanged (1.33; 95% CI 0.93 to 1.89). Among all men of the same age in the recruitment areas, the excess was 82% (1.82; 95% CI 1.67 to 1.98). The smokers' excess was about 40% of that. The authors concluded that educational differences in Finland are likely to mainly reflect more heavy smoking among less-educated men. They noted that asbestos exposure in building and construction was not fully reported.

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: Analysis of cohort data from a randomized placebo-controlled prevention trial (ATBC Study), compared with national census-based mortality data
• Who was studied: 14 011 Finnish male smokers aged 50–69, recruited 1985–1988 from 14 areas in South-Western Finland (alpha-tocopherol-only and placebo groups of the ATBC Study), followed for mortality to the end of April 1993 (average 5.5 years). For comparison, all men aged 50–69 in the 1985 census resident in the recruitment areas.
• Exposure: Educational attainment (basic: elementary school or less, versus higher). Smoking history: age at starting, years smoked, cigarettes per day, inhalation. Occupational asbestos exposure, asked as ever being employed in asbestos mining, asbestos production or asbestos insulating occupations. No fiber type was specified. About 2% of men reported such work (2% of basic-educated, 1% of higher-educated).
• Main results:
  • 238 men in the ATBC cohort died of lung cancer during follow-up (200 basic-educated, 38 higher-educated).
  • Age-adjusted lung cancer mortality was 32% higher among basic-educated men than among better-educated men in the ATBC Study (RR 1.32; 95% CI 0.93–1.87).
  • Further adjustment for smoking variables, asbestos exposure and interactions between asbestos and smoking gave RR 1.33 (95% CI 0.93–1.89) for basic-educated men. The authors reported that these adjustments had no effect on the excess.
  • Differences in smoking behaviour between the education groups in the ATBC cohort were very small.
  • In the general Finnish male population aged 50–69 in the same areas, age-adjusted lung cancer mortality of basic-educated men was 82% higher than that of higher-educated men (RR 1.82; 95% CI 1.67–1.98). The excess among the ATBC smokers was about 40% of this.
• The authors' conclusion: The authors concluded that educational differences in lung cancer mortality in the total Finnish population are likely to mainly reflect the higher proportion of heavy smokers among less-educated people.
• Limitations the authors state:
  • Adjustment for asbestos was only partial. Residual confounding is likely because asbestos exposure in the building and construction industry was not fully reported.
  • Limitations of the survey questions on smoking and inaccurate responses cannot be completely ruled out as explanations.
  • Education in the national data came from a register of certificates, which differs somewhat from the ATBC self-reports.
  • The mortality difference found among long-term heavy smokers may not be the same at lower smoking levels or among non-smokers.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Death Certificate, rate ratio, Occupational Exposure, Asbestos Exposure.

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