Marriage to a smoker and lung cancer risk

Our plain-English summary of Marriage to a smoker and lung cancer risk, by C.G. Humble, J.M. Samet, D.R. Pathak (American Journal of Public Health, 1987).

The study

• Authors: C.G. Humble, J.M. Samet, D.R. Pathak
• Journal: American Journal of Public Health
• Published: 1987;77(5):598-602
• Cited by: 69 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000975).

Abstract

As part of a population-based case-control study of lung cancer in New Mexico, we have collected data on spouses' tobacco smoking habits and on-the-job exposure to asbestos. The present analyses include 609 cases and 781 controls with known passive and personal smoking status, of whom 28 were lifelong nonsmokers with lung cancer. While no effect of spouse cigarette smoking was found among current or former smokers, never smokers married to smokers had about a two-fold increased risk of lung cancer. Lung cancer risk in never smokers also increased with duration of exposure to a smoking spouse, but not with increasing number of cigarettes smoked per day by the spouse. Our findings are consistent with previous reports of elevated risk for lung cancer among never smokers living with a spouse who smokes cigarettes.

In plain English

This New Mexico case-control study examined lung cancer in people married to smokers and in women whose husbands may have worked with asbestos. It included 609 cases and 781 controls; 28 cases were interview-reported never smokers, four of whom hospital records showed had smoked. Among current and former smokers, a smoking spouse showed no effect. Among never smokers, a spouse who smoked cigarettes only was linked to higher odds: odds ratio 2.9 (90 per cent confidence interval 1.3 to 6.7) in simple comparisons and 2.2 (1.0 to 4.9) in adjusted models. Risk rose with exposure duration only in simple comparisons, not with spouse's daily cigarettes. The authors concluded that the results indicated increased risk in never smokers but not in active smokers. Possible asbestos exposure was reported only for women; when the husband held a job judged possibly asbestos-related, odds ratios were 2.5 (90 per cent confidence interval 1.0 to 6.4) in never smokers and 0.8 (0.4 to 1.6) in ever smokers. They noted that other secondhand smoke sources were unmeasured and that more surrogate interviews for cases could bias results upward.

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: Population-based case-control study, with analyses of marriage to a smoker and of indirect asbestos exposure through a spouse's job
• Who was studied: 609 lung cancer cases and 781 controls with known passive and personal smoking status. Interviews classified 28 of the cases as lifelong nonsmokers. For four of these 28, hospital chart summaries showed smoking. Cases were Hispanic and non-Hispanic residents of New Mexico under 85 years old with primary lung cancer, identified by the New Mexico Tumor Registry. They were diagnosed from 1980 to 1982, with additional cases added from December 1983 to November 1984. Controls came from random telephone sampling and from a Medicare roster of residents 65 and older. They were frequency-matched to cases for sex, ethnicity and 10-year age group.
• Exposure: Two exposures were studied. The first was the spouse's tobacco smoking: cigarettes, cigars and pipes, with duration and amount smoked daily. The second was possible indirect asbestos exposure, measured two ways. One measure counted a spouse's job that appeared on a list judged to possibly involve asbestos. The other counted a spouse who was described as exposed to asbestos at work. No fiber types were named.
• Main results:
  • Among current and former cigarette smokers, marriage to a smoker showed no effect. For exposure to cigarettes only, all subjects combined, the odds ratio was 1.2 (90% CI 0.9, 1.6) for current smokers. For former smokers it was 1.1 (0.8, 1.5).
  • Among never smokers, all subjects, a spouse's cigarette smoking regardless of pipe or cigar use was associated with a three-fold increased risk: OR 3.2 (90% CI 1.5, 7.2). For exposure to cigarettes only, spouses who smoked other tobacco products were excluded; there the age-adjusted OR was 2.9 (CI 1.3, 6.7).
  • In logistic regression models for never smokers, all subjects, the OR was 2.2 (90% CI 1.0, 4.9) for cigarettes only and 2.6 (1.2, 5.6) for cigarettes and/or pipe or cigar. These were lower than in the cross-tabulations, but all point estimates were above 1.
  • Restricting the analysis to females lowered the odds ratios but did not change the pattern. For never-smoking females, the crude OR for cigarettes only was 1.8 (90% CI 0.6, 5.4).
  • Duration of exposure was examined in never smokers, all subjects. In cross-tabulations the OR was 2.2 (90% CI 0.8, 5.9) for 26 years or less of exposure and 2.7 (1.0, 7.1) for more than 26 years. The logistic models did not show an increase with duration: short duration OR 1.9 (CI 0.7, 4.7), long duration OR 1.8 (CI 0.7, 4.5).
  • The spouse's daily cigarettes were examined in never smokers, all subjects. The OR was higher when the spouse smoked 20 or fewer cigarettes a day (OR 2.8, 90% CI 1.2, 6.6) than when the spouse smoked more than 20 (OR 2.2, 0.6, 7.3).
  • Potential indirect asbestos exposure was reported only for females. Among female controls, 14.5 per cent were classed as exposed based on the husband's work history. Based on a report of the husband's occupational exposure to asbestos, 8.2 per cent were classed as exposed.
  • Logistic models for women gave odds ratios for two asbestos measures.
• Spouse employed in an asbestos-related job: OR 2.5 (90% CI 1.0, 6.4) for never-smoking women; OR 0.8 (0.4, 1.6) for women who had ever smoked.
• Spouse reported as exposed at work: OR 2.2 (0.5, 9.2) for never-smoking women; OR 1.4 (0.6, 3.2) for ever-smoking women.
  The odds ratios were higher for never-smoking females.
• The authors' conclusion: The authors concluded that the results indicated increased lung cancer risk from marriage to a cigarette smoker in never smokers, but not in active smokers. They described this as about a two-fold increase, consistent with previous reports. For possible indirect asbestos exposure through a spouse's job, they reported associated elevations of lung cancer risk, more evident in never smokers. They described the size of this effect as surprisingly large.
• Limitations the authors state:
  • Passive smoke exposure was assessed only from a smoking spouse. Exposure from other smokers at home and at work was not assessed, so subjects may have been misclassified on total passive smoke exposure.
  • Surrogate interviews (generally with a surviving spouse or a child) were needed for 52 per cent of cases, including 19 of the 28 never smokers. This proportion was much higher for cases than for controls. The authors stated that this could have introduced differential misclassification and biased results upward.
  • For four of the 28 never-smoker cases, hospital records conflicted with the interview about smoking. These four were kept in the reported analyses. The authors reported that findings were unchanged when they were removed.
  • Only eight males had never smoked cigarettes, so analyses were done for females alone and for all subjects combined.
  • There were too few subjects to adjust simultaneously for ethnicity and age.
  • Too few controls had surrogate interviews, so the controls could not be split by type of interview.

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, Case-Control Study, Habit.

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