Cigarette smoking, alcohol intake, and risk of glioma in the NIH-AARP Diet and Health Study

Background: Although cigarette smoking and alcohol drinking increase the risk of several cancers and certain components of cigarette smoke and alcohol can penetrate the blood–brain barrier, it remains unclear whether these exposures influence the risk of glioma. Methods: We examined the associations between cigarette smoking, alcohol intake, and risk of glioma in the National Institutes of Health-AARP Diet and Health Study, a prospective study of 477 095 US men and women ages 50–71 years at baseline. Hazard ratios (HRs) and 95 % confidence intervals (CIs) were calculated using models with age as the time metric and adjusted for sex, race/ethnicity, education, and marital status. Results: During a median 10.5 person-years of follow-up, 492 men and 212 women were diagnosed with first primary glioma. Among men, current, heavier smoking was associated with a reduced risk of glioma compared with never smoking, but this was based on only nine cases. No associations were observed between smoking behaviours and glioma risk in women. Greater alcohol consumption was associated with a decreased risk of glioma, particularly among men (42 drinks per day vs o1 drink per week: HR 0.67, 95 % CI 0.51–0.90). Conclusion: Smoking and alcohol drinking do not appear to increase the risk of glioma. Apart from a few established risk factors (e.g., exposure to ionising radiation, male sex, non-Hispanic white race/ethnicity) and probable protective factors (e.g., history of allergies), little is known regarding the aetiology of malignant brain tumours, which have a 5-year survival rate of only 34 % (Bondy et al, 2008; Dolecek et al, 2012). Cigarette smoking and alcohol drinking are associated with increased risks of several types of cancer, including those of the oral cavity, pharynx, esophagus, larynx, stomach, colon, and rectum (Bagnardi et al, 2001; US Department of Health and Human Services, 2004). In addition, components of cigarett