Why are lung cancer rate trends so different in the United States and United kingdom?
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.
Lee
Peter N
PN
P. N. Lee Statistics and Computing Ltd, 17 Cedar Road, Sutton, Surrey SM2 5DA, UK. PeterLee@pnlee.demon.co.uk
Forey
Barbara A
BA
D000328:Adult; D000367:Age Factors; D000368:Aged; D000397:Air Pollution / Q000009:adverse effects / Q000032:analysis; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000139:chemically induced / Q000453:epidemiology* / Q000401:mortality; D008297:Male; D008385:Marijuana Smoking / Q000453:epidemiology; D008875:Middle Aged; D015233:Models, Statistical; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology; D006113:United Kingdom / Q000453:epidemiology; D014481:United States / Q000453:epidemiology