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Smoking Exacts a Heavier Toll Than Previously Expected

By Todd Neale, Staff Writer, MedPage Today – Published: January 22, 2009 – Reviewed by Zalman S. Agus, MD; Emeritus Professor – University of Pennsylvania School of Medicine.

DAVIS, Calif., Jan. 22 — Exposure to tobacco smoke may be causing a much greater proportion of cancer deaths than previously estimated, researchers here said.

Among Massachusetts men, selected as a representative sample, there was a close correlation in changes in mortality rates from lung cancer and other cancers, Bruce Leistikow, M.D., of the University of California Davis, and colleagues reported online in BMC Cancer.

This suggested that the fraction of all cancer deaths attributable to smoking was 73%. A 2001 government estimate using data from the Cancer Prevention Study II, placed the fraction at 34%, according to Dr. Leistikow.

“The full impacts of tobacco smoke, including secondhand smoke, have been overlooked in the rush to examine such potential cancer factors as diet and environmental contaminants,” Dr. Leistikow said. “As it turns out, much of the answer was probably smoking all along.”

Action Points

Explain to interested patients that this study suggested that exposure to tobacco smoke accounts for almost three-quarters of all cancer deaths, not just those from lung cancer.

Point out that the study was performed using data from men living in Massachusetts and that the results may not be applicable to other states or females.

Previous estimates of the impact of smoke exposure on cancer death have been made using methods that are not universally applicable across population subgroups and that rely almost exclusively on self-reported smoking measures, according to Dr. Leistikow and colleagues.

The findings suggest “that increased attention should be paid to smoking prevention in healthcare reforms and health promotion campaigns,” he said.

Indeed, recent efforts to prevent smoking seem to be paying off. The rate of deaths from all causes that were attributed to smoking dropped from 288 to 263 deaths per 100,000 people from 1996-1999 to 2000-2004, according to a report in the Jan. 23 issue of the CDC’s Morbidity and Mortality Weekly Report.

Previous estimates of the impact of smoke exposure on cancer death have been made using methods that are not universally applicable across population subgroups, according to Dr. Leistikow and colleagues.

So they used a simpler and more representative and less biased method for assessing the impact that involved examining the associations between mortality rates for lung and all other cancers.

Lung cancer death rate was used as an indicator of cumulative smoke load.

Using data from the National Center for Health Statistics, the researchers examined cancer mortality rates among men living in Massachusetts from 1979 to 2003.

Rates peaked around 1992 and then declined steadily through 2003.

A scatter plot of mortality rates for lung cancer and for other cancers showed a strong association between the two over the study period, which suggests “that tobacco smoke load is a potential cause of most prematurely fatal cancers in this population,” the researchers said.

The percentage of all cancer deaths attributable to tobacco smoke exposure was 73% for all men and 74% for men ages 30 to 74.

In absolute terms, that works out to be 196 deaths per 100,000 men.

The researchers said the study findings were strengthened because of the inclusion of all non-lung cancers, the use of sizeable, representative, and recent male populations, and the use of age-adjusted death rates.

Previous estimates of the impact of tobacco smoke exposure on cancer mortality sometimes used outdated lists of which cancers were related to smoking, relied on smoking status as a measure of tobacco smoke exposure, and involved smaller and racially homogenous populations, they said.

The researchers acknowledged some limitations of the current analysis, including the potential for extrapolation from population-level associations to individual risks to yield inaccurate estimates, the inability to apply the results to females, to residents of other states, or to longer-term trends, and the inability to distinguish between types of smoke exposure.

Future research should focus on developing biochemical measures of individual exposure to tobacco smoke, studying cancer disparities among larger and more racially diverse populations, and examining why the association between mortality rates from lung and other cancers varies in different populations, they said.

Research needs aside, they concluded, “the improved ability to assess the population effect of tobacco smoke damage can be used to better inform cancer control policy, including the regulation of tobacco products and smoking in public places.”

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