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Cigarette smoking and risk of glioma: A
prospective cohort study
Silvera SA, Miller AB, Rohan TE
Department of Epidemiology and Population Health, Albert Einstein
College of Medicine, Bronx, NY, USA.
The etiology of glioma, the most commonly diagnosed malignant brain
tumor among adults in the United States, is poorly understood.
N-nitroso compounds are known
carcinogens, which are found in cigarette smoke and can induce gliomas
in rats.
On this basis, it has been
hypothesized that cigarette smoking may be associated with an
increased risk of glioma.
We investigated the association
between cigarette smoking and glioma risk in the National Breast
Screening Study, which included 89,835 Canadian women aged 40-59 years
at recruitment between 1980 and 1985.
Linkages to national cancer and
mortality databases yielded data on cancer incidence and deaths from
all causes, respectively, with follow-up ending between 1998 and
2000.
Cox proportional hazard models were
used to estimate hazard ratios (HRs) and 95% confidence intervals
(CIs) for the association between cigarette smoking and risk of
glioma.
During a mean of 16.4 years of
follow-up, we observed 120 incident glioma cases.
Among ever smokers, women who
reported having quit smoking had a 51% increase in risk of glioma
compared with never smokers (HR = 1.51, 95% CI = 0.97-2.34), while
current smokers did not appear to have an increase in risk.
When the association with former
smokers was further examined by years since quitting, women who had
quit smoking >10 years before baseline were at a decreased risk of
glioma compared with women who had quit within the 10 years prior to
baseline (HR = 0.55, 95% CI = 0.29-1.07), indicating that the
association between former smokers and glioma may be driven by women,
who recently quit smoking.
Compared with nonsmokers, duration of
cigarette smoking, number of cigarettes smoked per day and pack-years
of smoking were associated with increased glioma risk, although the
increases in risk were relatively modest.
The present study provides some
support for a positive association between cigarette smoking and risk
of glioma.
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