Why are lung cancer rate trends so different in the United States and United kingdom?

Our plain-English summary of Why are lung cancer rate trends so different in the United States and United kingdom?, by P.N. Lee, B.A. Forey (Inhalation Toxicology, 2003).

The study

• Authors: P.N. Lee, B.A. Forey
• Journal: Inhalation Toxicology
• Published: 2003;15(9):909-49
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Over the period 1951-1995, lung cancer rates in men aged 35-74 yr more than doubled in the United States but declined slightly in the United Kingdom. In women, rates rose about sevenfold in the United States but only about threefold in the United Kingdom. To investigate whether these very different trends in lung cancer risk could be explained by smoking habits, trends in smoking were compared in the two countries and a multistage model was used to predict lung cancer rates from detailed data on age of starting and stopping smoking, amount smoked per smoker, and sales-weighted average tar levels. In both countries, there was a similar switch to filter cigarettes, reduction in tar levels and the average age of starting to smoke, and decline in prevalence of smoking in women aged under 50 yr and in men. Although some differences were evident, most notably in older women where prevalence of smoking and consumption per adult has increased more in the United States, these trends do not appear to explain the markedly different trends in lung cancer, evident in both sexes and all age groups. The multistage analyses confirmed these tentative conclusions-the differing trends in smoking in the two countries could not explain the markedly differing trends in lung cancer. Lung cancer trends in the United Kingdom were found to be clearly more favorable than expected on the basis of smoking trends, while trends in the United States were less favorable. In sensitivity analyses, these conclusions were found not to be materially dependent on the precise methods used, including whether tar reduction was or was not assumed to be beneficial. The explanation for these findings must lie in changes over time, differing in the two countries, in aspects of smoking not considered in these analyses and/or in exposure to other risk factors. Evidence relating to a number of possible such smoking variables (including type of tobacco, curing, use of pesticides and additives, and butt length) or other risk factors (including air pollution, radon, asbestos, obesity, and marijuana) is discussed, but no clear explanation of the findings is offered. Further research is urgently needed to investigate the causes of these apparently anomalous trends in lung cancer and in smoking habits. Criticism is also presented of the views recently expressed by the authors of NCI Monograph 13 that tar reduction has been ineffective in lowering lung cancer risk and that trends in lung cancer in the United States fit in well with trends in smoking habits.

In plain English

The article compared US and UK lung cancer deaths and smoking, 1951 to 1995. It used WHO death data, smoking data and, for 1955 to 1985, a multistage model predicting lung cancer rates from smoking histories. In 1951 to 1955, age-adjusted rates per 100,000 per year at ages 35 to 74 were 59.0 (US men), 9.4 (US women), 128.2 (UK men) and 16.0 (UK women). By 1991 to 1995 they were 130.6, 65.0, 115.1 and 50.8. Smoking trends were broadly similar, with some differences, most notably a larger rise in smoking among older US women; consumption per adult also fell less in US than UK men. The model did not predict the rising US to England and Wales rate ratio; UK trends were more favorable, and US trends less favorable, than smoking predicted. Asbestos was not in the model; comparing published estimates of asbestos-related lung cancers with the unexplained US rise, the authors argued asbestos seemingly could not fully explain it. The authors concluded the smoking factors studied could not explain the differing trends.

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 national lung cancer mortality statistics and smoking-habit data (sales and survey data). Lung cancer rates were predicted from smoking histories using a multistage model of carcinogenesis and compared with observed rates. The study included sensitivity analyses.
• Who was studied: Lung cancer deaths by gender and age (35 to 74) in the United States, United Kingdom, and England and Wales, 1951 to 1995, from WHO data. Model analyses covered 1955 to 1985, at ages 35 to 74 for the US and 35 to 64 for England and Wales. US smoking histories came from the Health Interview Survey of some 50,000 men and women (1978 to 1980). England and Wales histories came from the Health and Lifestyle Study.
• Exposure: Cigarette smoking was the exposure modeled: prevalence of smoking, age of starting and stopping, amount smoked per smoker, the switch to filter cigarettes, and sales-weighted average tar yield. Asbestos was not included in the model. The discussion considered it as a possible other risk factor, using published estimates of asbestos-related lung cancers.
• Main results:
  • In 1951 to 1955, US lung cancer mortality rates (per 100,000 per year, ages 35 to 74, age adjusted) were 59.0 in men and 9.4 in women.
  • In 1951 to 1955, UK rates were 128.2 in men and 16.0 in women.
  • By 1991 to 1995, US rates had risen to 130.6 in men and 65.0 in women.
  • By 1991 to 1995, UK rates were 115.1 in men and 50.8 in women.
  • The US-to-UK rate ratios increased over the period. For ages 40 to 44, 55 to 59 and 70 to 74, the factors were 2.8, 3.2 and 1.9 in males and 2.1, 3.1 and 1.6 in females.
  • Average age of starting to smoke fell similarly in both countries. No obvious difference between the US and England and Wales was seen.
  • Among older US women, smoking prevalence rose much more than in the UK. In 1986 to 1990 it was twofold or more greater than in 1951 to 1955 at ages 60 to 74. The authors called this the most notable difference between the countries.
  • In men, cigarette consumption per adult per day declined less in the US than in the UK between 1951 to 1955 and 1986 to 1990. In the UK it fell by about 40% at ages 25 to 54 and 30% at ages 55 to 74. In the US the falls were about 30% and 10%.
  • In England and Wales, modeled lung cancer trends were generally more favorable than smoking trends predicted. The US results were very different, with the discrepancy generally in the opposite direction.
  • The authors' analyses indicated almost 28,000 more US lung cancer deaths at ages 35 to 74 in 1985 than predicted from 1955 rates and smoking-predicted trends.
  • In the discussion, the authors cited published estimates (Lilienfeld et al., 1988) of US lung cancers attributable to past asbestos exposure. They called a range of 1200 to 6000 per year more plausible, with 3068 deaths the median estimate. They judged that asbestos-related lung cancers seemed unlikely to have risen by more than 2000 to 3000 over the second half of the 20th century, considerably less than the unexplained increase.
  • The authors argued that asbestos seemingly could not be the full explanation of the unexplained US increase. Their reason was that its effects in nonsmokers appear at least as great as in smokers, while lung cancer rates in US nonsmokers showed little increase.
• The authors' conclusion: The authors concluded that the differing US and UK lung cancer trends cannot be explained by trends in the major aspects of smoking they studied. They considered various other smoking and non-smoking factors but found no clear reason.
• Limitations the authors state:
  • Data on smoking in the first half of the 20th century are quite limited.
  • The authors listed several data problems: the reliability of reported smoking histories, bias from the differential mortality of smokers and nonsmokers, possibly nonrepresentative survey subjects, unreliable early data on amount smoked, and difficulty allowing for compensation for reduced tar. They said sensitivity analyses addressed many of these.
  • Cigar and pipe smoking were not taken into account. The authors judged that any resulting bias would not be substantial.
  • The analyses did not formally account for the switch from plain to filter cigarettes. The authors considered this unimportant because tar reduction was modeled.

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, Habit.

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