Benefits of quitting smoking apparent years later
While quitting smoking remains the number one means of reducing a smoker's risk for fatal lung cancer, real declines in death risk only appear between 15-20 years after individuals kick the habit, according to new study findings.
``The excess mortality risk associated with smoking can be avoided by never smoking and can be reduced among smokers only by becoming a long-term former smoker,'' write Dr. James Enstrom and Dr. Clark Heath, Jr. of the University of California, Los Angeles. Their report is published in the September issue of the journal Epidemiology.
The study authors studied the impact of quitting smoking on death rates over the past 40 years in a group of over 118,000 men and women enrolled in the American Cancer Society's Cancer Prevention Study.
The authors hypothesized that the smoking-related death rates of former smokers and never smokers would converge -- that is, become the same -- as a consequence of smoking cessation.
Cigarette smoking rates declined substantially between 1959 and 1994/1999 in the study participants, the report indicates -- from 46% to just 3% for men and from 32% to 2% for women. Even among men and women who smoked at the beginning of the study, there has been ``almost total cessation,'' according to the authors. Only 7% of men and 7% of women who smoked in 1959 still smoked by 1994/1999.
However, quitting did not translate quickly or directly into reduced death rates, the authors report. Even among former smokers, ``the death rates for those who had quit for less than 1 and (between) 1-4 years were close to the death rates for current smokers.''
In fact, death rates of former smokers only began to match those of never-smokers ``after 15-20 years of (smoking) cessation,'' according to the researchers.
Overall, smoking cessation had little real impact on long-term death rates in the group as a whole. But the researchers point out that most of the ex-smokers in the study group ``were long-term smokers who quit after the age of 55 years.'' These heavy, long-term smokers tended to have much higher death rates compared with the smaller number of smokers who quit earlier in life.
``These results explain why there has not yet been a substantial decline in the lung cancer death rate among older US males as a whole,'' the researchers say, ``and why the lung cancer death rate among US females has risen so much despite a considerable amount of smoking cessation during the past 35 years.''