Using detailed patient data and mathematical modeling programs, a US–international team of investigators has concluded that in the United States, public health efforts, beginning in the 1950s and highlighted by the US Surgeon General’s Report on Smoking and Health in 1964, prevented nearly 800,000 deaths from lung cancer between 1975 and 2000. The findings are reported in the April 4, 2012 issue of the Journal of the National Cancer Institute (JNCI).
While the study results underscore the positive impact of tobacco-control efforts in the United States since the mid 1960s—including restrictions on smoking in public places, cigarette price and tax increases, limits on underage access to cigarettes, and public awareness campaigns—they highlight the need to remain vigilant in public health efforts to promote smoking cessation.
The lead author of the NCI-funded study is Suresh H. Moolgavkar, MD, PhD, from the Program in Biostatistics and Biomathematics at Fred Hutchinson Cancer Research Center, Seattle, Washington. Other groups in the research consortium are from Erasmus Medical Center, Rotterdam, Netherlands; Pacific Institute for Research and Evaluation, Calverton, Maryland; Rice University and M.D. Anderson Cancer Center, Houston, Texas; Massachusetts General Hospital and Harvard Medical School, Cambridge, Massachusetts; and Yale University, New Haven, Connecticut. All research teams in the study are part of the NCI’s Cancer Intervention and Surveillance Modeling Network.
For the study, six groups of investigators developed independent models to estimate the number of lung cancer deaths averted in 1975–2000. They accessed patient information from cohort, case–control, or registry data and applied mathematical descriptions of the relationships between smoking behaviors and lung cancer, with consideration of factors such as number of cigarettes smoked daily, age at which smoking was initiated, and number of years quit.
Each modeling group used the population and smoking data to develop a smoking history generator, which simulates detailed individual-level smoking and other-cause mortality histories to allow estimation of lung cancer mortality rates in the population.
The data were stratified by sex and birth decade (1890–1970), and the prevalence of smoking and lung cancer deaths was considered under three scenarios: actual tobacco control (ATC), based on historical changes in rates of smoking; no tobacco control (NTC), based on predicted smoking rates if tobacco control had not been enacted; and complete tobacco control (CTC), which considers what might have happened if all smoking ceased in 1965, following the 1964 US Surgeon General’s report.
All models shared common attributes and were similarly structured. The study investigators concluded that, while the different models “yielded a range of results for the numbers of lung cancer deaths among the three smoking scenarios…estimates of the fraction of lung cancer deaths averted were reasonably consistent across models.”
The investigators assessed the difference between the NTC and observed numbers to obtain an estimate of the numbers of lung cancer deaths averted in all models. They found that, in the absence of tobacco control programs and policies, if smoking behaviors had not changed after the Surgeon General’s report, an additional 552,000 men and 243,000 women in the United States would have died of lung cancer.
Another striking finding was that, if all cigarette smokers in the United States had quit following release of the 1964 Surgeon General’s report and there were no new smokers in the United States, about 2.5 million people would not have died from lung cancer (that is, 1.6 million men and 883,000 women would not have been diagnosed with the disease).
The investigators only studied data through 2000, the latest year for which they had sufficiently detailed information for their models when the project was initiated. However, they did note that in the United States, “consistent with trends for continued gains due to past tobacco control policies, smoking prevalence continued to fall from 23.2% in 2000 to 20.6% in 2008. Much of this decrease can be attributed to tobacco-control policies, especially the cigarette price increases in 1998–1999.”
This decline in smoking in the United States in 2000 alone is significant, as it translates to about 70,000 lung cancer deaths averted (in about 44,000 men and 26,000 women). Still, the investigators said, these numbers represent only about one-third (32%) “of the lung cancer deaths that potentially could have been averted during the period 1975–2000” and nearly half (44%) of lung cancer deaths that could have been averted in the year 2000 alone.
A note from the editors in the JNCI article pointed out several limitations of the study, including the lack of data on other environmental exposures related to lung cancer incidence (eg, environmental tobacco smoke, radon exposure, diet, and air pollution) and on non-cigarette forms of tobacco use. In addition, they said, the researchers did not address the relative contributions of decreased smoking initiation and increased smoking cessation.