Thursday, May 08, 2008


Smoking Cessation Leads to Early and Late Mortality Benefits


By Charles Bankhead

BOSTON, 08 may 2009--Within five years of a woman's last cigarette, excess vascular risk has virtually disappeared, but lung mortality remains elevated for 15 additional years, according to the Nurses' Health Study.
After 22 years of follow-up, data from the study showed that smoking cessation reduced the risk of every cause-specific mortality outcome evaluated, Stacey Kenfield, Sc.D., of the Harvard School of Public Health, and colleagues reported in the May 7 issue of the Journal of the American Medical Association.
The full mortality benefit of smoking cessation accrued over 20 years, but over a variable timeframe, they added.
"Our findings indicate that 64% of deaths in current smokers and 28% of deaths in past smokers are attributable to smoking," they added. "Quitting reduces the excess mortality rates for all major causes of death examined."
Launched in 1976, the Nurses' Health Study originally involved 121,700 female RNs in the United States, ages 30 to 55. Participants provided detailed information about their medical history and risk factors for cancer, heart disease, and other conditions. In 1980, 28% of the participants were smokers, 26% former smokers, and 46% never smokers. By 2002, only 8% of surviving participants were smokers.
From the outset, the information has been updated by biennial questionnaires. After 12 years of follow-up, the data showed that current smoking and starting at a younger age increased the risk of all-cause and cause-specific mortality. With an additional 10 years of follow-up, the current study had the statistical strength to characterize smoking's effect on more causes of death, particularly respiratory disease and cancer.
Dr. Kenfield and colleagues analyzed data comprising 12,483 deaths: 4,485 (35.9%) among never-smokers, 3,602 (28.9%) among smokers, and 4,396 (35.2%) among former smokers. The total number of deaths consisted of:
2,957 vascular deaths
759 respiratory deaths
1,237 lung cancer deaths
2,104 smoking-related cancer deaths (including lung)
3,805 deaths due to other types of cancer
2,858 deaths due to other causes
Current smokers had almost a three-fold greater mortality risk compared with never-smokers (HR 2.81, 95% CI 2.68 to 2.95). There was a similar difference in analyses limited to major cause-specific mortality. Risks increased significantly with the number of cigarettes smoked daily. Former smokers had a 23% excess mortality risk.
Smokers had a seven-fold greater risk for smoking-related cancer deaths, as identified by the 2004 surgeon general's report (HR 7.25, 95% CI 6.43 to 8.18) and a 60% greater risk for other cancer deaths. The hazard ratios for former smokers were 2.33 and 1.09, respectively.
For all respiratory causes of death, smoking increased the risk 10-fold compared with never smokers. Former smokers had a four-fold greater risk.
Smokers had more than a three-fold greater risk of vascular death compared with never smokers. Most of the excess risk had disappeared in former smokers, whose hazard ratio was 1.32 versus never smokers.
The authors reported no financial disclosures.
Primary source: Journal of the American Medical AssociationSource reference:Kenfield SA, et al "Smoking and smoking cessation in relation to mortality in women" JAMA 2008; 299: 2037-2047.

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